[PATCH] rebase -i: improve error message when picking merge

[PATCH] rebase -i: improve error message when picking merge

[Phillip Wood via GitGitGadget]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

The only todo commands that accept a merge commit are "merge" and
"reset". All the other commands like "pick" or "reword" fail when they
try to pick a a merge commit and print the message

    error: commit abc123 is a merge but no -m option was given.

followed by a hint about the command being rescheduled. This message is
designed to help the user when they cherry-pick a merge and forget to
pass "-m". For users who are rebasing the message is confusing as there
is no way for rebase to cherry-pick the merge.

Improve the user experience by detecting the error when the todo list is
parsed rather than waiting for the "pick" command to fail and print a
message recommending the "merge" command instead. We recommend "merge"
rather than "exec git cherry-pick -m ..." on the assumption that
cherry-picking merges is relatively rare and it is more likely that the
user chose "pick" by a mistake.

It would be possible to support cherry-picking merges by allowing the
user to pass "-m" to "pick" commands but that adds complexity to do
something that can already be achieved with

    exec git cherry-pick -m1 abc123

The change is relatively straight forward but is complicated slightly as
we now need to tell the parser if we're rebasing or not.

Reported-by: Stefan Haller <lists@haller-berlin.de>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
    rebase -i: improve error message when picking merge

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1672%2Fphillipwood%2Frebase-reject-merges-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1672/phillipwood/rebase-reject-merges-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1672

 builtin/rebase.c              |  2 +-
 rebase-interactive.c          |  7 ++---
 sequencer.c                   | 49 ++++++++++++++++++++++++++++++-----
 sequencer.h                   |  2 +-
 t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++
 5 files changed, 81 insertions(+), 12 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 5b086f651a6..a33e41c44da 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -297,7 +297,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
 	else {
 		discard_index(&the_index);
 		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
-						&todo_list))
+						&todo_list, 1))
 			BUG("unusable todo list");
 
 		ret = complete_action(the_repository, &replay, flags,
diff --git a/rebase-interactive.c b/rebase-interactive.c
index d9718409b3d..78d5ed1a41d 100644
--- a/rebase-interactive.c
+++ b/rebase-interactive.c
@@ -114,7 +114,8 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
 	 * it.  If there is an error, we do not return, because the user
 	 * might want to fix it in the first place. */
 	if (!initial)
-		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
+		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf,
+							todo_list, 1) |
 			file_exists(rebase_path_dropped());
 
 	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
@@ -134,7 +135,7 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
 	if (initial && new_todo->buf.len == 0)
 		return -3;
 
-	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
+	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo, 1)) {
 		fprintf(stderr, _(edit_todo_list_advice));
 		return -4;
 	}
@@ -234,7 +235,7 @@ int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_
 	int res = 0;
 
 	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
-		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
+		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup, 1);
 		res = todo_list_check(&backup, todo_list);
 	}
 
diff --git a/sequencer.c b/sequencer.c
index 91de546b323..cf808c24d20 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2550,8 +2550,37 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
 	return 0;
 }
 
+static int error_merge_commit(enum todo_command command)
+{
+	switch(command) {
+	case TODO_PICK:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s'"),
+			     todo_command_info[command].str, "merge -C");
+
+	case TODO_REWORD:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s'"),
+			     todo_command_info[command].str, "merge -c");
+
+	case TODO_EDIT:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s' followed by '%s'"),
+			     todo_command_info[command].str,
+			     "merge -C", "break");
+
+	case TODO_FIXUP:
+	case TODO_SQUASH:
+		return error(_("cannot squash merge commit into another commit"));
+
+	default:
+		BUG("unexpected todo_command");
+	}
+}
+
 static int parse_insn_line(struct repository *r, struct todo_item *item,
-			   const char *buf, const char *bol, char *eol)
+			   const char *buf, const char *bol, char *eol,
+			   int rebasing)
 {
 	struct object_id commit_oid;
 	char *end_of_object_name;
@@ -2655,7 +2684,12 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 		return status;
 
 	item->commit = lookup_commit_reference(r, &commit_oid);
-	return item->commit ? 0 : -1;
+	if (!item->commit)
+		return -1;
+	if (rebasing && item->command != TODO_MERGE &&
+	    item->commit->parents && item->commit->parents->next)
+		return error_merge_commit(item->command);
+	return 0;
 }
 
 int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
@@ -2686,7 +2720,7 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
 }
 
 int todo_list_parse_insn_buffer(struct repository *r, char *buf,
-				struct todo_list *todo_list)
+				struct todo_list *todo_list, int rebasing)
 {
 	struct todo_item *item;
 	char *p = buf, *next_p;
@@ -2704,7 +2738,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
 
 		item = append_new_todo(todo_list);
 		item->offset_in_buf = p - todo_list->buf.buf;
-		if (parse_insn_line(r, item, buf, p, eol)) {
+		if (parse_insn_line(r, item, buf, p, eol, rebasing)) {
 			res = error(_("invalid line %d: %.*s"),
 				i, (int)(eol - p), p);
 			item->command = TODO_COMMENT + 1;
@@ -2852,7 +2886,8 @@ static int read_populate_todo(struct repository *r,
 	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
 		return -1;
 
-	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
+	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list,
+					  is_rebase_i(opts));
 	if (res) {
 		if (is_rebase_i(opts))
 			return error(_("please fix this using "
@@ -2882,7 +2917,7 @@ static int read_populate_todo(struct repository *r,
 		struct todo_list done = TODO_LIST_INIT;
 
 		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
-		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
+		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done, 1))
 			todo_list->done_nr = count_commands(&done);
 		else
 			todo_list->done_nr = 0;
@@ -6286,7 +6321,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
 	strbuf_release(&buf2);
 	/* Nothing is done yet, and we're reparsing, so let's reset the count */
 	new_todo.total_nr = 0;
-	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
+	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo, 1) < 0)
 		BUG("invalid todo list after expanding IDs:\n%s",
 		    new_todo.buf.buf);
 
diff --git a/sequencer.h b/sequencer.h
index dcef7bb99c0..ed2c4b38514 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -136,7 +136,7 @@ struct todo_list {
 }
 
 int todo_list_parse_insn_buffer(struct repository *r, char *buf,
-				struct todo_list *todo_list);
+				struct todo_list *todo_list, int rebasing);
 int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
 			    const char *file, const char *shortrevisions,
 			    const char *shortonto, int num, unsigned flags);
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 64b641002e4..20b8589ad07 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -2203,6 +2203,39 @@ test_expect_success 'bad labels and refs rejected when parsing todo list' '
 	test_path_is_missing execed
 '
 
+test_expect_success 'non-merge commands reject merge commits' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	git checkout E &&
+	git merge I &&
+	oid=$(git rev-parse HEAD) &&
+	cat >todo <<-EOF &&
+	pick $oid
+	reword $oid
+	edit $oid
+	fixup $oid
+	squash $oid
+	EOF
+	(
+		set_replace_editor todo &&
+		test_must_fail git rebase -i HEAD 2>actual
+	) &&
+	cat >expect <<-EOF &&
+	error: ${SQ}pick${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ}
+	error: invalid line 1: pick $oid
+	error: ${SQ}reword${SQ} does not accept merge commits, please use ${SQ}merge -c${SQ}
+	error: invalid line 2: reword $oid
+	error: ${SQ}edit${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ} followed by ${SQ}break${SQ}
+	error: invalid line 3: edit $oid
+	error: cannot squash merge commit into another commit
+	error: invalid line 4: fixup $oid
+	error: cannot squash merge commit into another commit
+	error: invalid line 5: squash $oid
+	You can fix this with ${SQ}git rebase --edit-todo${SQ} and then run ${SQ}git rebase --continue${SQ}.
+	Or you can abort the rebase with ${SQ}git rebase --abort${SQ}.
+	EOF
+	test_cmp expect actual
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged

base-commit: c875e0b8e036c12cfbf6531962108a063c7a821c
-- 
gitgitgadget

Re: [PATCH] rebase -i: improve error message when picking merge

[phillip.wood123]

If anyone has time to review this I'd be very grateful. I've added a 
couple of people to the cc list who have recently contributed to the 
sequencer but if anyone else fancies taking a look please do.

Thanks

Phillip

On 26/02/2024 10:58, Phillip Wood via GitGitGadget wrote:
> From: Phillip Wood <phillip.wood@dunelm.org.uk>
> 
> The only todo commands that accept a merge commit are "merge" and
> "reset". All the other commands like "pick" or "reword" fail when they
> try to pick a a merge commit and print the message
> 
>      error: commit abc123 is a merge but no -m option was given.
> 
> followed by a hint about the command being rescheduled. This message is
> designed to help the user when they cherry-pick a merge and forget to
> pass "-m". For users who are rebasing the message is confusing as there
> is no way for rebase to cherry-pick the merge.
> 
> Improve the user experience by detecting the error when the todo list is
> parsed rather than waiting for the "pick" command to fail and print a
> message recommending the "merge" command instead. We recommend "merge"
> rather than "exec git cherry-pick -m ..." on the assumption that
> cherry-picking merges is relatively rare and it is more likely that the
> user chose "pick" by a mistake.
> 
> It would be possible to support cherry-picking merges by allowing the
> user to pass "-m" to "pick" commands but that adds complexity to do
> something that can already be achieved with
> 
>      exec git cherry-pick -m1 abc123
> 
> The change is relatively straight forward but is complicated slightly as
> we now need to tell the parser if we're rebasing or not.
> 
> Reported-by: Stefan Haller <lists@haller-berlin.de>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---
>      rebase -i: improve error message when picking merge
> 
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1672%2Fphillipwood%2Frebase-reject-merges-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1672/phillipwood/rebase-reject-merges-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/1672
> 
>   builtin/rebase.c              |  2 +-
>   rebase-interactive.c          |  7 ++---
>   sequencer.c                   | 49 ++++++++++++++++++++++++++++++-----
>   sequencer.h                   |  2 +-
>   t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++
>   5 files changed, 81 insertions(+), 12 deletions(-)
> 
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 5b086f651a6..a33e41c44da 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -297,7 +297,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
>   	else {
>   		discard_index(&the_index);
>   		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
> -						&todo_list))
> +						&todo_list, 1))
>   			BUG("unusable todo list");
>   
>   		ret = complete_action(the_repository, &replay, flags,
> diff --git a/rebase-interactive.c b/rebase-interactive.c
> index d9718409b3d..78d5ed1a41d 100644
> --- a/rebase-interactive.c
> +++ b/rebase-interactive.c
> @@ -114,7 +114,8 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>   	 * it.  If there is an error, we do not return, because the user
>   	 * might want to fix it in the first place. */
>   	if (!initial)
> -		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
> +		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf,
> +							todo_list, 1) |
>   			file_exists(rebase_path_dropped());
>   
>   	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
> @@ -134,7 +135,7 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>   	if (initial && new_todo->buf.len == 0)
>   		return -3;
>   
> -	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
> +	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo, 1)) {
>   		fprintf(stderr, _(edit_todo_list_advice));
>   		return -4;
>   	}
> @@ -234,7 +235,7 @@ int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_
>   	int res = 0;
>   
>   	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
> -		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
> +		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup, 1);
>   		res = todo_list_check(&backup, todo_list);
>   	}
>   
> diff --git a/sequencer.c b/sequencer.c
> index 91de546b323..cf808c24d20 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -2550,8 +2550,37 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
>   	return 0;
>   }
>   
> +static int error_merge_commit(enum todo_command command)
> +{
> +	switch(command) {
> +	case TODO_PICK:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -C");
> +
> +	case TODO_REWORD:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -c");
> +
> +	case TODO_EDIT:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s' followed by '%s'"),
> +			     todo_command_info[command].str,
> +			     "merge -C", "break");
> +
> +	case TODO_FIXUP:
> +	case TODO_SQUASH:
> +		return error(_("cannot squash merge commit into another commit"));
> +
> +	default:
> +		BUG("unexpected todo_command");
> +	}
> +}
> +
>   static int parse_insn_line(struct repository *r, struct todo_item *item,
> -			   const char *buf, const char *bol, char *eol)
> +			   const char *buf, const char *bol, char *eol,
> +			   int rebasing)
>   {
>   	struct object_id commit_oid;
>   	char *end_of_object_name;
> @@ -2655,7 +2684,12 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
>   		return status;
>   
>   	item->commit = lookup_commit_reference(r, &commit_oid);
> -	return item->commit ? 0 : -1;
> +	if (!item->commit)
> +		return -1;
> +	if (rebasing && item->command != TODO_MERGE &&
> +	    item->commit->parents && item->commit->parents->next)
> +		return error_merge_commit(item->command);
> +	return 0;
>   }
>   
>   int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
> @@ -2686,7 +2720,7 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
>   }
>   
>   int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list)
> +				struct todo_list *todo_list, int rebasing)
>   {
>   	struct todo_item *item;
>   	char *p = buf, *next_p;
> @@ -2704,7 +2738,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>   
>   		item = append_new_todo(todo_list);
>   		item->offset_in_buf = p - todo_list->buf.buf;
> -		if (parse_insn_line(r, item, buf, p, eol)) {
> +		if (parse_insn_line(r, item, buf, p, eol, rebasing)) {
>   			res = error(_("invalid line %d: %.*s"),
>   				i, (int)(eol - p), p);
>   			item->command = TODO_COMMENT + 1;
> @@ -2852,7 +2886,8 @@ static int read_populate_todo(struct repository *r,
>   	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
>   		return -1;
>   
> -	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
> +	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list,
> +					  is_rebase_i(opts));
>   	if (res) {
>   		if (is_rebase_i(opts))
>   			return error(_("please fix this using "
> @@ -2882,7 +2917,7 @@ static int read_populate_todo(struct repository *r,
>   		struct todo_list done = TODO_LIST_INIT;
>   
>   		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
> -		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
> +		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done, 1))
>   			todo_list->done_nr = count_commands(&done);
>   		else
>   			todo_list->done_nr = 0;
> @@ -6286,7 +6321,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>   	strbuf_release(&buf2);
>   	/* Nothing is done yet, and we're reparsing, so let's reset the count */
>   	new_todo.total_nr = 0;
> -	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
> +	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo, 1) < 0)
>   		BUG("invalid todo list after expanding IDs:\n%s",
>   		    new_todo.buf.buf);
>   
> diff --git a/sequencer.h b/sequencer.h
> index dcef7bb99c0..ed2c4b38514 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -136,7 +136,7 @@ struct todo_list {
>   }
>   
>   int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list);
> +				struct todo_list *todo_list, int rebasing);
>   int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
>   			    const char *file, const char *shortrevisions,
>   			    const char *shortonto, int num, unsigned flags);
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 64b641002e4..20b8589ad07 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -2203,6 +2203,39 @@ test_expect_success 'bad labels and refs rejected when parsing todo list' '
>   	test_path_is_missing execed
>   '
>   
> +test_expect_success 'non-merge commands reject merge commits' '
> +	test_when_finished "test_might_fail git rebase --abort" &&
> +	git checkout E &&
> +	git merge I &&
> +	oid=$(git rev-parse HEAD) &&
> +	cat >todo <<-EOF &&
> +	pick $oid
> +	reword $oid
> +	edit $oid
> +	fixup $oid
> +	squash $oid
> +	EOF
> +	(
> +		set_replace_editor todo &&
> +		test_must_fail git rebase -i HEAD 2>actual
> +	) &&
> +	cat >expect <<-EOF &&
> +	error: ${SQ}pick${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ}
> +	error: invalid line 1: pick $oid
> +	error: ${SQ}reword${SQ} does not accept merge commits, please use ${SQ}merge -c${SQ}
> +	error: invalid line 2: reword $oid
> +	error: ${SQ}edit${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ} followed by ${SQ}break${SQ}
> +	error: invalid line 3: edit $oid
> +	error: cannot squash merge commit into another commit
> +	error: invalid line 4: fixup $oid
> +	error: cannot squash merge commit into another commit
> +	error: invalid line 5: squash $oid
> +	You can fix this with ${SQ}git rebase --edit-todo${SQ} and then run ${SQ}git rebase --continue${SQ}.
> +	Or you can abort the rebase with ${SQ}git rebase --abort${SQ}.
> +	EOF
> +	test_cmp expect actual
> +'
> +
>   # This must be the last test in this file
>   test_expect_success '$EDITOR and friends are unchanged' '
>   	test_editor_unchanged
> 
> base-commit: c875e0b8e036c12cfbf6531962108a063c7a821c

Re: [PATCH] rebase -i: improve error message when picking merge

[Patrick Steinhardt]

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On Wed, Apr 03, 2024 at 02:42:19PM +0100, phillip.wood123@gmail.com wrote:
> If anyone has time to review this I'd be very grateful. I've added a couple
> of people to the cc list who have recently contributed to the sequencer but
> if anyone else fancies taking a look please do.
> 
> Thanks
> 
> Phillip

I ain't got much of a stake in this, but I've put in my 2c anyway. :)

Patrick

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Re: [PATCH] rebase -i: improve error message when picking merge

[Patrick Steinhardt]

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On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
> From: Phillip Wood <phillip.wood@dunelm.org.uk>
> 
> The only todo commands that accept a merge commit are "merge" and
> "reset". All the other commands like "pick" or "reword" fail when they
> try to pick a a merge commit and print the message
> 
>     error: commit abc123 is a merge but no -m option was given.
> 
> followed by a hint about the command being rescheduled. This message is
> designed to help the user when they cherry-pick a merge and forget to
> pass "-m". For users who are rebasing the message is confusing as there
> is no way for rebase to cherry-pick the merge.
> 
> Improve the user experience by detecting the error when the todo list is
> parsed rather than waiting for the "pick" command to fail and print a
> message recommending the "merge" command instead. We recommend "merge"
> rather than "exec git cherry-pick -m ..." on the assumption that
> cherry-picking merges is relatively rare and it is more likely that the
> user chose "pick" by a mistake.
> 
> It would be possible to support cherry-picking merges by allowing the
> user to pass "-m" to "pick" commands but that adds complexity to do
> something that can already be achieved with
> 
>     exec git cherry-pick -m1 abc123

Okay. I think it's reasonable to abort early and give some advice here.
It's certainly a lot more user friendly than to abort during the rebase.
And if we ever gain the ability to e.g. `pick -m1` in the instruction
sheet directly we can adapt accordingly.

> The change is relatively straight forward but is complicated slightly as
> we now need to tell the parser if we're rebasing or not.
> 
> Reported-by: Stefan Haller <lists@haller-berlin.de>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---
>     rebase -i: improve error message when picking merge
> 
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1672%2Fphillipwood%2Frebase-reject-merges-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1672/phillipwood/rebase-reject-merges-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/1672
> 
>  builtin/rebase.c              |  2 +-
>  rebase-interactive.c          |  7 ++---
>  sequencer.c                   | 49 ++++++++++++++++++++++++++++++-----
>  sequencer.h                   |  2 +-
>  t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++
>  5 files changed, 81 insertions(+), 12 deletions(-)
> 
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 5b086f651a6..a33e41c44da 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -297,7 +297,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
>  	else {
>  		discard_index(&the_index);
>  		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
> -						&todo_list))
> +						&todo_list, 1))

I think these booleans are somewhat hard to read. I may be
overengineering this, so please feel free to push back, but would it
make more sense to introduce a `unsigned flags` field and then have a
`PARSE_INSN_IS_REBASING` flag?

>  			BUG("unusable todo list");
>  
>  		ret = complete_action(the_repository, &replay, flags,
> diff --git a/rebase-interactive.c b/rebase-interactive.c
> index d9718409b3d..78d5ed1a41d 100644
> --- a/rebase-interactive.c
> +++ b/rebase-interactive.c
> @@ -114,7 +114,8 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>  	 * it.  If there is an error, we do not return, because the user
>  	 * might want to fix it in the first place. */
>  	if (!initial)
> -		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
> +		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf,
> +							todo_list, 1) |
>  			file_exists(rebase_path_dropped());
>  
>  	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
> @@ -134,7 +135,7 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>  	if (initial && new_todo->buf.len == 0)
>  		return -3;
>  
> -	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
> +	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo, 1)) {
>  		fprintf(stderr, _(edit_todo_list_advice));
>  		return -4;
>  	}
> @@ -234,7 +235,7 @@ int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_
>  	int res = 0;
>  
>  	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
> -		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
> +		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup, 1);
>  		res = todo_list_check(&backup, todo_list);
>  	}
>  
> diff --git a/sequencer.c b/sequencer.c
> index 91de546b323..cf808c24d20 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -2550,8 +2550,37 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
>  	return 0;
>  }
>  
> +static int error_merge_commit(enum todo_command command)
> +{
> +	switch(command) {
> +	case TODO_PICK:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -C");

I wonder how actionable these commands are. Can we give the full command
that the user can use instead, including the commit ID?

That raises another question though: how exactly is the user supposed to
perform the merge? Should they merge the merge commit, resulting in two
merge commits? Should they pick one of the sides, and if so, which one?
I guess the answer is "it depends", which makes it harder for us to come
up with actionable advice here.

> +	case TODO_REWORD:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -c");

I was about to suggest that the above two cases should be merged. But
then I realized that it's "merge -c" here, but "merge -C" in the first
case.

Patrick

> +	case TODO_EDIT:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s' followed by '%s'"),
> +			     todo_command_info[command].str,
> +			     "merge -C", "break");
> +
> +	case TODO_FIXUP:
> +	case TODO_SQUASH:
> +		return error(_("cannot squash merge commit into another commit"));
> +
> +	default:
> +		BUG("unexpected todo_command");
> +	}
> +}
> +
>  static int parse_insn_line(struct repository *r, struct todo_item *item,
> -			   const char *buf, const char *bol, char *eol)
> +			   const char *buf, const char *bol, char *eol,
> +			   int rebasing)
>  {
>  	struct object_id commit_oid;
>  	char *end_of_object_name;
> @@ -2655,7 +2684,12 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
>  		return status;
>  
>  	item->commit = lookup_commit_reference(r, &commit_oid);
> -	return item->commit ? 0 : -1;
> +	if (!item->commit)
> +		return -1;
> +	if (rebasing && item->command != TODO_MERGE &&
> +	    item->commit->parents && item->commit->parents->next)
> +		return error_merge_commit(item->command);
> +	return 0;
>  }
>  
>  int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
> @@ -2686,7 +2720,7 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
>  }
>  
>  int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list)
> +				struct todo_list *todo_list, int rebasing)
>  {
>  	struct todo_item *item;
>  	char *p = buf, *next_p;
> @@ -2704,7 +2738,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>  
>  		item = append_new_todo(todo_list);
>  		item->offset_in_buf = p - todo_list->buf.buf;
> -		if (parse_insn_line(r, item, buf, p, eol)) {
> +		if (parse_insn_line(r, item, buf, p, eol, rebasing)) {
>  			res = error(_("invalid line %d: %.*s"),
>  				i, (int)(eol - p), p);
>  			item->command = TODO_COMMENT + 1;
> @@ -2852,7 +2886,8 @@ static int read_populate_todo(struct repository *r,
>  	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
>  		return -1;
>  
> -	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
> +	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list,
> +					  is_rebase_i(opts));
>  	if (res) {
>  		if (is_rebase_i(opts))
>  			return error(_("please fix this using "
> @@ -2882,7 +2917,7 @@ static int read_populate_todo(struct repository *r,
>  		struct todo_list done = TODO_LIST_INIT;
>  
>  		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
> -		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
> +		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done, 1))
>  			todo_list->done_nr = count_commands(&done);
>  		else
>  			todo_list->done_nr = 0;
> @@ -6286,7 +6321,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>  	strbuf_release(&buf2);
>  	/* Nothing is done yet, and we're reparsing, so let's reset the count */
>  	new_todo.total_nr = 0;
> -	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
> +	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo, 1) < 0)
>  		BUG("invalid todo list after expanding IDs:\n%s",
>  		    new_todo.buf.buf);
>  
> diff --git a/sequencer.h b/sequencer.h
> index dcef7bb99c0..ed2c4b38514 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -136,7 +136,7 @@ struct todo_list {
>  }
>  
>  int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list);
> +				struct todo_list *todo_list, int rebasing);
>  int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
>  			    const char *file, const char *shortrevisions,
>  			    const char *shortonto, int num, unsigned flags);
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 64b641002e4..20b8589ad07 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -2203,6 +2203,39 @@ test_expect_success 'bad labels and refs rejected when parsing todo list' '
>  	test_path_is_missing execed
>  '
>  
> +test_expect_success 'non-merge commands reject merge commits' '
> +	test_when_finished "test_might_fail git rebase --abort" &&
> +	git checkout E &&
> +	git merge I &&
> +	oid=$(git rev-parse HEAD) &&
> +	cat >todo <<-EOF &&
> +	pick $oid
> +	reword $oid
> +	edit $oid
> +	fixup $oid
> +	squash $oid
> +	EOF
> +	(
> +		set_replace_editor todo &&
> +		test_must_fail git rebase -i HEAD 2>actual
> +	) &&
> +	cat >expect <<-EOF &&
> +	error: ${SQ}pick${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ}
> +	error: invalid line 1: pick $oid
> +	error: ${SQ}reword${SQ} does not accept merge commits, please use ${SQ}merge -c${SQ}
> +	error: invalid line 2: reword $oid
> +	error: ${SQ}edit${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ} followed by ${SQ}break${SQ}
> +	error: invalid line 3: edit $oid
> +	error: cannot squash merge commit into another commit
> +	error: invalid line 4: fixup $oid
> +	error: cannot squash merge commit into another commit
> +	error: invalid line 5: squash $oid
> +	You can fix this with ${SQ}git rebase --edit-todo${SQ} and then run ${SQ}git rebase --continue${SQ}.
> +	Or you can abort the rebase with ${SQ}git rebase --abort${SQ}.
> +	EOF
> +	test_cmp expect actual
> +'
> +
>  # This must be the last test in this file
>  test_expect_success '$EDITOR and friends are unchanged' '
>  	test_editor_unchanged
> 
> base-commit: c875e0b8e036c12cfbf6531962108a063c7a821c
> -- 
> gitgitgadget
> 

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Re: [PATCH] rebase -i: improve error message when picking merge

[phillip.wood123]

Hi Patrick

On 04/04/2024 07:08, Patrick Steinhardt wrote:
> On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
> [...]
>> diff --git a/builtin/rebase.c b/builtin/rebase.c
>> index 5b086f651a6..a33e41c44da 100644
>> --- a/builtin/rebase.c
>> +++ b/builtin/rebase.c
>> @@ -297,7 +297,7 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
>>   	else {
>>   		discard_index(&the_index);
>>   		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
>> -						&todo_list))
>> +						&todo_list, 1))
> 
> I think these booleans are somewhat hard to read. I may be
> overengineering this, so please feel free to push back, but would it
> make more sense to introduce a `unsigned flags` field and then have a
> `PARSE_INSN_IS_REBASING` flag?

I agree the boolean is a bit opaque, I don't think they are that unusual 
in the code base but that doesn't mean they're readable. I had hoped to 
pass an instance of 'struct replay_opts' to parse_insn_line() and then 
call is_rebase_i() which there which would have been nicer. 
Unfortunately "git rebase --edit-todo" does not instantiate an instance 
of that struct as it is not needed for editing the todo list so I went 
with a boolean instead. There are one or two places where we need to use 
is_rebase_i() for this when calling parse_insn_line() which makes using 
an unsigned flags argument a bit messy. I'll have a look and see how 
hard it would be to ensure we always have a valid 'struct replay_opts' 
when calling parse_insn_line().

>> +static int error_merge_commit(enum todo_command command)
>> +{
>> +	switch(command) {
>> +	case TODO_PICK:
>> +		return error(_("'%s' does not accept merge commits, "
>> +			       "please use '%s'"),
>> +			     todo_command_info[command].str, "merge -C");
> 
> I wonder how actionable these commands are. Can we give the full command
> that the user can use instead, including the commit ID?

The calling function also prints the offending line so the user can see 
the commit details there.

> That raises another question though: how exactly is the user supposed to
> perform the merge? Should they merge the merge commit, resulting in two
> merge commits? Should they pick one of the sides, and if so, which one?
> I guess the answer is "it depends", which makes it harder for us to come
> up with actionable advice here.

I agree it would be nice to be more precise but I'm not sure we can tell 
what the user is actually trying to do so I think the best we can do is 
point them in the direction of the 'merge' command.

>> +	case TODO_REWORD:
>> +		return error(_("'%s' does not accept merge commits, "
>> +			       "please use '%s'"),
>> +			     todo_command_info[command].str, "merge -c");
> 
> I was about to suggest that the above two cases should be merged. But
> then I realized that it's "merge -c" here, but "merge -C" in the first
> case.

Yes, it is a subtle difference.

Thanks very much for taking a look at this

Phillip

> Patrick
> 
>> +	case TODO_EDIT:
>> +		return error(_("'%s' does not accept merge commits, "
>> +			       "please use '%s' followed by '%s'"),
>> +			     todo_command_info[command].str,
>> +			     "merge -C", "break");
>> +
>> +	case TODO_FIXUP:
>> +	case TODO_SQUASH:
>> +		return error(_("cannot squash merge commit into another commit"));
>> +
>> +	default:
>> +		BUG("unexpected todo_command");
>> +	}
>> +}
>> +
>>   static int parse_insn_line(struct repository *r, struct todo_item *item,
>> -			   const char *buf, const char *bol, char *eol)
>> +			   const char *buf, const char *bol, char *eol,
>> +			   int rebasing)
>>   {
>>   	struct object_id commit_oid;
>>   	char *end_of_object_name;
>> @@ -2655,7 +2684,12 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
>>   		return status;
>>   
>>   	item->commit = lookup_commit_reference(r, &commit_oid);
>> -	return item->commit ? 0 : -1;
>> +	if (!item->commit)
>> +		return -1;
>> +	if (rebasing && item->command != TODO_MERGE &&
>> +	    item->commit->parents && item->commit->parents->next)
>> +		return error_merge_commit(item->command);
>> +	return 0;
>>   }
>>   
>>   int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
>> @@ -2686,7 +2720,7 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
>>   }
>>   
>>   int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>> -				struct todo_list *todo_list)
>> +				struct todo_list *todo_list, int rebasing)
>>   {
>>   	struct todo_item *item;
>>   	char *p = buf, *next_p;
>> @@ -2704,7 +2738,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>>   
>>   		item = append_new_todo(todo_list);
>>   		item->offset_in_buf = p - todo_list->buf.buf;
>> -		if (parse_insn_line(r, item, buf, p, eol)) {
>> +		if (parse_insn_line(r, item, buf, p, eol, rebasing)) {
>>   			res = error(_("invalid line %d: %.*s"),
>>   				i, (int)(eol - p), p);
>>   			item->command = TODO_COMMENT + 1;
>> @@ -2852,7 +2886,8 @@ static int read_populate_todo(struct repository *r,
>>   	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
>>   		return -1;
>>   
>> -	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
>> +	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list,
>> +					  is_rebase_i(opts));
>>   	if (res) {
>>   		if (is_rebase_i(opts))
>>   			return error(_("please fix this using "
>> @@ -2882,7 +2917,7 @@ static int read_populate_todo(struct repository *r,
>>   		struct todo_list done = TODO_LIST_INIT;
>>   
>>   		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
>> -		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
>> +		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done, 1))
>>   			todo_list->done_nr = count_commands(&done);
>>   		else
>>   			todo_list->done_nr = 0;
>> @@ -6286,7 +6321,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>>   	strbuf_release(&buf2);
>>   	/* Nothing is done yet, and we're reparsing, so let's reset the count */
>>   	new_todo.total_nr = 0;
>> -	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
>> +	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo, 1) < 0)
>>   		BUG("invalid todo list after expanding IDs:\n%s",
>>   		    new_todo.buf.buf);
>>   
>> diff --git a/sequencer.h b/sequencer.h
>> index dcef7bb99c0..ed2c4b38514 100644
>> --- a/sequencer.h
>> +++ b/sequencer.h
>> @@ -136,7 +136,7 @@ struct todo_list {
>>   }
>>   
>>   int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>> -				struct todo_list *todo_list);
>> +				struct todo_list *todo_list, int rebasing);
>>   int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
>>   			    const char *file, const char *shortrevisions,
>>   			    const char *shortonto, int num, unsigned flags);
>> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
>> index 64b641002e4..20b8589ad07 100755
>> --- a/t/t3404-rebase-interactive.sh
>> +++ b/t/t3404-rebase-interactive.sh
>> @@ -2203,6 +2203,39 @@ test_expect_success 'bad labels and refs rejected when parsing todo list' '
>>   	test_path_is_missing execed
>>   '
>>   
>> +test_expect_success 'non-merge commands reject merge commits' '
>> +	test_when_finished "test_might_fail git rebase --abort" &&
>> +	git checkout E &&
>> +	git merge I &&
>> +	oid=$(git rev-parse HEAD) &&
>> +	cat >todo <<-EOF &&
>> +	pick $oid
>> +	reword $oid
>> +	edit $oid
>> +	fixup $oid
>> +	squash $oid
>> +	EOF
>> +	(
>> +		set_replace_editor todo &&
>> +		test_must_fail git rebase -i HEAD 2>actual
>> +	) &&
>> +	cat >expect <<-EOF &&
>> +	error: ${SQ}pick${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ}
>> +	error: invalid line 1: pick $oid
>> +	error: ${SQ}reword${SQ} does not accept merge commits, please use ${SQ}merge -c${SQ}
>> +	error: invalid line 2: reword $oid
>> +	error: ${SQ}edit${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ} followed by ${SQ}break${SQ}
>> +	error: invalid line 3: edit $oid
>> +	error: cannot squash merge commit into another commit
>> +	error: invalid line 4: fixup $oid
>> +	error: cannot squash merge commit into another commit
>> +	error: invalid line 5: squash $oid
>> +	You can fix this with ${SQ}git rebase --edit-todo${SQ} and then run ${SQ}git rebase --continue${SQ}.
>> +	Or you can abort the rebase with ${SQ}git rebase --abort${SQ}.
>> +	EOF
>> +	test_cmp expect actual
>> +'
>> +
>>   # This must be the last test in this file
>>   test_expect_success '$EDITOR and friends are unchanged' '
>>   	test_editor_unchanged
>>
>> base-commit: c875e0b8e036c12cfbf6531962108a063c7a821c
>> -- 
>> gitgitgadget
>>

Re: [PATCH] rebase -i: improve error message when picking merge

[Rubén Justo]

On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
> From: Phillip Wood <phillip.wood@dunelm.org.uk>
> 
> The only todo commands that accept a merge commit are "merge" and
> "reset". All the other commands like "pick" or "reword" fail when they
> try to pick a a merge commit and print the message
> 
>     error: commit abc123 is a merge but no -m option was given.
> 
> followed by a hint about the command being rescheduled. This message is
> designed to help the user when they cherry-pick a merge and forget to
> pass "-m". For users who are rebasing the message is confusing as there
> is no way for rebase to cherry-pick the merge.
> 
> Improve the user experience by detecting the error when the todo list is
> parsed rather than waiting for the "pick" command to fail and print a
> message recommending the "merge" command instead. We recommend "merge"
> rather than "exec git cherry-pick -m ..." on the assumption that
> cherry-picking merges is relatively rare and it is more likely that the
> user chose "pick" by a mistake.
> 
> It would be possible to support cherry-picking merges by allowing the
> user to pass "-m" to "pick" commands but that adds complexity to do
> something that can already be achieved with
> 
>     exec git cherry-pick -m1 abc123
> 
> The change is relatively straight forward but is complicated slightly as
> we now need to tell the parser if we're rebasing or not.
> 
> Reported-by: Stefan Haller <lists@haller-berlin.de>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---

Hi Phillip.

The change makes sense, but this is confusing to me:

With this ...

	$ GIT_EDITOR='echo pick 17381ab62a >' ./git rebase -i HEAD
	error: 'pick' does not accept merge commits, please use 'merge -C'
	error: invalid line 1: pick 17381ab62a
	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
	Or you can abort the rebase with 'git rebase --abort'.

... I find these repeated messages confusing:

	$ GIT_EDITOR=: ./git rebase --edit-todo
	error: 'pick' does not accept merge commits, please use 'merge -C'
	error: invalid line 1: pick 17381ab62a
	error: 'pick' does not accept merge commits, please use 'merge -C'
	error: invalid line 1: pick 17381ab62a
	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
	Or you can abort the rebase with 'git rebase --abort'.

Re: [PATCH] rebase -i: improve error message when picking merge

[phillip.wood123]

Hi Rubén

Thanks for trying this out.

On 04/04/2024 20:44, Rubén Justo wrote:
> On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
> The change makes sense, but this is confusing to me:
> 
> With this ...
> 
> 	$ GIT_EDITOR='echo pick 17381ab62a >' ./git rebase -i HEAD
> 	error: 'pick' does not accept merge commits, please use 'merge -C'
> 	error: invalid line 1: pick 17381ab62a
> 	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
> 	Or you can abort the rebase with 'git rebase --abort'.
> 
> ... I find these repeated messages confusing:
> 
> 	$ GIT_EDITOR=: ./git rebase --edit-todo
> 	error: 'pick' does not accept merge commits, please use 'merge -C'
> 	error: invalid line 1: pick 17381ab62a

The two lines above are printed when "rebase --edit-todo" loads the todo 
list for the user to edit. With a real editor rather than ":" we would 
then print

     hint: Waiting for your editor to close the file ...

Then hopefully the user would fix the errors. If not then when the 
editor had finished we'd print the remaining errors  as below.

> 	error: 'pick' does not accept merge commits, please use 'merge -C'
> 	error: invalid line 1: pick 17381ab62a
> 	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
> 	Or you can abort the rebase with 'git rebase --abort'.

I think that printing the error messages when the todo list is parsed 
before it is given to the user to edit is helpful as it reminds the user 
what the problem is. Your test looks confusing because it doesn't really 
simulate the user editing the todo list.

Best Wishes

Phillip

Re: [PATCH] rebase -i: improve error message when picking merge

[Rubén Justo]

On Fri, Apr 05, 2024 at 10:30:37AM +0100, phillip.wood123@gmail.com wrote:
> Hi Rubén
> 
> Thanks for trying this out.
> 
> On 04/04/2024 20:44, Rubén Justo wrote:
> > On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
> > The change makes sense, but this is confusing to me:
> > 
> > With this ...
> > 
> > 	$ GIT_EDITOR='echo pick 17381ab62a >' ./git rebase -i HEAD
> > 	error: 'pick' does not accept merge commits, please use 'merge -C'
> > 	error: invalid line 1: pick 17381ab62a
> > 	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
> > 	Or you can abort the rebase with 'git rebase --abort'.
> > 
> > ... I find these repeated messages confusing:
> > 
> > 	$ GIT_EDITOR=: ./git rebase --edit-todo
> > 	error: 'pick' does not accept merge commits, please use 'merge -C'
> > 	error: invalid line 1: pick 17381ab62a
> 
> The two lines above are printed when "rebase --edit-todo" loads the todo
> list for the user to edit. With a real editor rather than ":" we would then
> print
> 
>     hint: Waiting for your editor to close the file ...
> 
> Then hopefully the user would fix the errors. If not then when the editor
> had finished we'd print the remaining errors  as below.
> 
> > 	error: 'pick' does not accept merge commits, please use 'merge -C'
> > 	error: invalid line 1: pick 17381ab62a
> > 	You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
> > 	Or you can abort the rebase with 'git rebase --abort'.
> 
> I think that printing the error messages when the todo list is parsed before
> it is given to the user to edit is helpful as it reminds the user what the
> problem is. Your test looks confusing because it doesn't really simulate the
> user editing the todo list.

Certainly, the test was not clear to express my confusion.

The ones that are printed _before_ the editor is run are the ones that
confuse me, because when the user exits the editor we leave those
lines there:

	$ GIT_EDITOR='sed -i s/pick/merge/' ./git rebase --edit
	error: 'pick' does not accept merge commits, please use 'merge -C'
	error: invalid line 1: pick 17381ab62a

But maybe it is my interpretation.  Your reasoning of giving it as a
help to the user makes sense.

Thank you for your explanations.

> Best Wishes
> 
> Phillip

Re: [PATCH] rebase -i: improve error message when picking merge

[phillip.wood123]

Hi Rubén

On 06/04/2024 15:24, Rubén Justo wrote:
> On Fri, Apr 05, 2024 at 10:30:37AM +0100, phillip.wood123@gmail.com wrote:
>> On 04/04/2024 20:44, Rubén Justo wrote:
>>> On Mon, Feb 26, 2024 at 10:58:07AM +0000, Phillip Wood via GitGitGadget wrote:
>>> ... I find these repeated messages confusing:
>>>
>> I think that printing the error messages when the todo list is parsed before
>> it is given to the user to edit is helpful as it reminds the user what the
>> problem is. Your test looks confusing because it doesn't really simulate the
>> user editing the todo list.
> 
> Certainly, the test was not clear to express my confusion.
> 
> The ones that are printed _before_ the editor is run are the ones that
> confuse me, because when the user exits the editor we leave those
> lines there:
> 
> 	$ GIT_EDITOR='sed -i s/pick/merge/' ./git rebase --edit
> 	error: 'pick' does not accept merge commits, please use 'merge -C'
> 	error: invalid line 1: pick 17381ab62a
> 
> But maybe it is my interpretation.  Your reasoning of giving it as a
> help to the user makes sense.

Ideally we'd clear the error messages when the user edited the todo list 
but there isn't an easy way to do that. In principle we could stop 
printing the error messages when parsing the list before it is edited 
but I'm not sure how easy that would be. The behavior you are seeing is 
already present is not changed by this patch - existing error messages 
behave in the same way.

Best Wishes

Phillip

> Thank you for your explanations.
> 
>> Best Wishes
>>
>> Phillip

[PATCH v2 0/2] rebase -i: improve error message when picking merge

[Phillip Wood via GitGitGadget]

If the user tries to pick a merge commit error out when parsing the todo
list rather than complaining when trying to pick the commit.

Thanks to Patrick and Rubén for their comments on V1. Changes since V1:

 * Rebased to avoid a conflict with jk/core-comment-string
 * Patch 1 is a new preparatory change that plumbs 'struct replay_opts'
   through to parse_insn_line()
 * Patch 2 is updated to use is_rebase_i() rather than requiring the caller
   to pass a boolean indicating whether we're rebasing.

Phillip Wood (2):
  rebase -i: pass struct replay_opts to parse_insn_line()
  rebase -i: improve error message when picking merge

 builtin/rebase.c              | 17 +++++++----
 rebase-interactive.c          | 21 ++++++++-----
 rebase-interactive.h          |  9 ++++--
 sequencer.c                   | 57 ++++++++++++++++++++++++++++-------
 sequencer.h                   |  4 +--
 t/t3404-rebase-interactive.sh | 33 ++++++++++++++++++++
 6 files changed, 111 insertions(+), 30 deletions(-)


base-commit: 19981daefd7c147444462739375462b49412ce33
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1672%2Fphillipwood%2Frebase-reject-merges-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1672/phillipwood/rebase-reject-merges-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1672

Range-diff vs v1:

 -:  ----------- > 1:  1bcf92c6105 rebase -i: pass struct replay_opts to parse_insn_line()
 1:  7726c496385 ! 2:  fbc6746e018 rebase -i: improve error message when picking merge
     @@ Commit message
      
              exec git cherry-pick -m1 abc123
      
     -    The change is relatively straight forward but is complicated slightly as
     -    we now need to tell the parser if we're rebasing or not.
     -
          Reported-by: Stefan Haller <lists@haller-berlin.de>
          Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
      
     - ## builtin/rebase.c ##
     -@@ builtin/rebase.c: static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
     - 	else {
     - 		discard_index(&the_index);
     - 		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
     --						&todo_list))
     -+						&todo_list, 1))
     - 			BUG("unusable todo list");
     - 
     - 		ret = complete_action(the_repository, &replay, flags,
     -
     - ## rebase-interactive.c ##
     -@@ rebase-interactive.c: int edit_todo_list(struct repository *r, struct todo_list *todo_list,
     - 	 * it.  If there is an error, we do not return, because the user
     - 	 * might want to fix it in the first place. */
     - 	if (!initial)
     --		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
     -+		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf,
     -+							todo_list, 1) |
     - 			file_exists(rebase_path_dropped());
     - 
     - 	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
     -@@ rebase-interactive.c: int edit_todo_list(struct repository *r, struct todo_list *todo_list,
     - 	if (initial && new_todo->buf.len == 0)
     - 		return -3;
     - 
     --	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
     -+	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo, 1)) {
     - 		fprintf(stderr, _(edit_todo_list_advice));
     - 		return -4;
     - 	}
     -@@ rebase-interactive.c: int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_
     - 	int res = 0;
     - 
     - 	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
     --		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
     -+		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup, 1);
     - 		res = todo_list_check(&backup, todo_list);
     - 	}
     - 
     -
       ## sequencer.c ##
      @@ sequencer.c: static int check_label_or_ref_arg(enum todo_command command, const char *arg)
       	return 0;
       }
       
     +-static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
      +static int error_merge_commit(enum todo_command command)
      +{
      +	switch(command) {
     @@ sequencer.c: static int check_label_or_ref_arg(enum todo_command command, const
      +	}
      +}
      +
     - static int parse_insn_line(struct repository *r, struct todo_item *item,
     --			   const char *buf, const char *bol, char *eol)
     -+			   const char *buf, const char *bol, char *eol,
     -+			   int rebasing)
     ++static int parse_insn_line(struct repository *r, struct replay_opts *opts,
     + 			   struct todo_item *item, const char *buf,
     + 			   const char *bol, char *eol)
       {
     - 	struct object_id commit_oid;
     - 	char *end_of_object_name;
     -@@ sequencer.c: static int parse_insn_line(struct repository *r, struct todo_item *item,
     +@@ sequencer.c: static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED
       		return status;
       
       	item->commit = lookup_commit_reference(r, &commit_oid);
      -	return item->commit ? 0 : -1;
      +	if (!item->commit)
      +		return -1;
     -+	if (rebasing && item->command != TODO_MERGE &&
     ++	if (is_rebase_i(opts) && item->command != TODO_MERGE &&
      +	    item->commit->parents && item->commit->parents->next)
      +		return error_merge_commit(item->command);
      +	return 0;
       }
       
       int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
     -@@ sequencer.c: int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
     - }
     - 
     - int todo_list_parse_insn_buffer(struct repository *r, char *buf,
     --				struct todo_list *todo_list)
     -+				struct todo_list *todo_list, int rebasing)
     - {
     - 	struct todo_item *item;
     - 	char *p = buf, *next_p;
     -@@ sequencer.c: int todo_list_parse_insn_buffer(struct repository *r, char *buf,
     - 
     - 		item = append_new_todo(todo_list);
     - 		item->offset_in_buf = p - todo_list->buf.buf;
     --		if (parse_insn_line(r, item, buf, p, eol)) {
     -+		if (parse_insn_line(r, item, buf, p, eol, rebasing)) {
     - 			res = error(_("invalid line %d: %.*s"),
     - 				i, (int)(eol - p), p);
     - 			item->command = TODO_COMMENT + 1;
     -@@ sequencer.c: static int read_populate_todo(struct repository *r,
     - 	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
     - 		return -1;
     - 
     --	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
     -+	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list,
     -+					  is_rebase_i(opts));
     - 	if (res) {
     - 		if (is_rebase_i(opts))
     - 			return error(_("please fix this using "
     -@@ sequencer.c: static int read_populate_todo(struct repository *r,
     - 		struct todo_list done = TODO_LIST_INIT;
     - 
     - 		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
     --		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
     -+		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done, 1))
     - 			todo_list->done_nr = count_commands(&done);
     - 		else
     - 			todo_list->done_nr = 0;
     -@@ sequencer.c: int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
     - 	strbuf_release(&buf2);
     - 	/* Nothing is done yet, and we're reparsing, so let's reset the count */
     - 	new_todo.total_nr = 0;
     --	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
     -+	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo, 1) < 0)
     - 		BUG("invalid todo list after expanding IDs:\n%s",
     - 		    new_todo.buf.buf);
     - 
     -
     - ## sequencer.h ##
     -@@ sequencer.h: struct todo_list {
     - }
     - 
     - int todo_list_parse_insn_buffer(struct repository *r, char *buf,
     --				struct todo_list *todo_list);
     -+				struct todo_list *todo_list, int rebasing);
     - int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
     - 			    const char *file, const char *shortrevisions,
     - 			    const char *shortonto, int num, unsigned flags);
      
       ## t/t3404-rebase-interactive.sh ##
      @@ t/t3404-rebase-interactive.sh: test_expect_success 'bad labels and refs rejected when parsing todo list' '

-- 
gitgitgadget

[PATCH v2 1/2] rebase -i: pass struct replay_opts to parse_insn_line()

[Phillip Wood via GitGitGadget]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

This new parameter will be used in the next commit. As adding the
parameter requires quite a few changes to plumb it through the call
chain these are separated into their own commit to avoid cluttering up
the next commit with incidental changes.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 builtin/rebase.c     | 17 +++++++++++------
 rebase-interactive.c | 21 +++++++++++++--------
 rebase-interactive.h |  9 ++++++---
 sequencer.c          | 22 ++++++++++++----------
 sequencer.h          |  4 ++--
 5 files changed, 44 insertions(+), 29 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 891f28468e8..a33a2ed413a 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -194,7 +194,7 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	return replay;
 }
 
-static int edit_todo_file(unsigned flags)
+static int edit_todo_file(unsigned flags, struct replay_opts *opts)
 {
 	const char *todo_file = rebase_path_todo();
 	struct todo_list todo_list = TODO_LIST_INIT,
@@ -205,7 +205,8 @@ static int edit_todo_file(unsigned flags)
 		return error_errno(_("could not read '%s'."), todo_file);
 
 	strbuf_stripspace(&todo_list.buf, comment_line_str);
-	res = edit_todo_list(the_repository, &todo_list, &new_todo, NULL, NULL, flags);
+	res = edit_todo_list(the_repository, opts, &todo_list, &new_todo,
+			     NULL, NULL, flags);
 	if (!res && todo_list_write_to_file(the_repository, &new_todo, todo_file,
 					    NULL, NULL, -1, flags & ~(TODO_LIST_SHORTEN_IDS)))
 		res = error_errno(_("could not write '%s'"), todo_file);
@@ -296,8 +297,8 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
 		error(_("could not generate todo list"));
 	else {
 		discard_index(&the_index);
-		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
-						&todo_list))
+		if (todo_list_parse_insn_buffer(the_repository, &replay,
+						todo_list.buf.buf, &todo_list))
 			BUG("unusable todo list");
 
 		ret = complete_action(the_repository, &replay, flags,
@@ -352,9 +353,13 @@ static int run_sequencer_rebase(struct rebase_options *opts)
 		replay_opts_release(&replay_opts);
 		break;
 	}
-	case ACTION_EDIT_TODO:
-		ret = edit_todo_file(flags);
+	case ACTION_EDIT_TODO: {
+		struct replay_opts replay_opts = get_replay_opts(opts);
+
+		ret = edit_todo_file(flags, &replay_opts);
+		replay_opts_release(&replay_opts);
 		break;
+	}
 	case ACTION_SHOW_CURRENT_PATCH: {
 		struct child_process cmd = CHILD_PROCESS_INIT;
 
diff --git a/rebase-interactive.c b/rebase-interactive.c
index c343e16fcdd..56fd7206a95 100644
--- a/rebase-interactive.c
+++ b/rebase-interactive.c
@@ -101,9 +101,10 @@ void append_todo_help(int command_count,
 	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_str);
 }
 
-int edit_todo_list(struct repository *r, struct todo_list *todo_list,
-		   struct todo_list *new_todo, const char *shortrevisions,
-		   const char *shortonto, unsigned flags)
+int edit_todo_list(struct repository *r, struct replay_opts *opts,
+		   struct todo_list *todo_list, struct todo_list *new_todo,
+		   const char *shortrevisions, const char *shortonto,
+		   unsigned flags)
 {
 	const char *todo_file = rebase_path_todo(),
 		*todo_backup = rebase_path_todo_backup();
@@ -114,7 +115,9 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
 	 * it.  If there is an error, we do not return, because the user
 	 * might want to fix it in the first place. */
 	if (!initial)
-		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
+		incorrect = todo_list_parse_insn_buffer(r, opts,
+							todo_list->buf.buf,
+							todo_list) |
 			file_exists(rebase_path_dropped());
 
 	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
@@ -134,13 +137,13 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
 	if (initial && new_todo->buf.len == 0)
 		return -3;
 
-	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
+	if (todo_list_parse_insn_buffer(r, opts, new_todo->buf.buf, new_todo)) {
 		fprintf(stderr, _(edit_todo_list_advice));
 		return -4;
 	}
 
 	if (incorrect) {
-		if (todo_list_check_against_backup(r, new_todo)) {
+		if (todo_list_check_against_backup(r, opts, new_todo)) {
 			write_file(rebase_path_dropped(), "%s", "");
 			return -4;
 		}
@@ -228,13 +231,15 @@ int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo)
 	return res;
 }
 
-int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_list)
+int todo_list_check_against_backup(struct repository *r,
+				   struct replay_opts *opts,
+				   struct todo_list *todo_list)
 {
 	struct todo_list backup = TODO_LIST_INIT;
 	int res = 0;
 
 	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
-		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
+		todo_list_parse_insn_buffer(r, opts, backup.buf.buf, &backup);
 		res = todo_list_check(&backup, todo_list);
 	}
 
diff --git a/rebase-interactive.h b/rebase-interactive.h
index 7239c60f791..8e5b181b334 100644
--- a/rebase-interactive.h
+++ b/rebase-interactive.h
@@ -3,17 +3,20 @@
 
 struct strbuf;
 struct repository;
+struct replay_opts;
 struct todo_list;
 
 void append_todo_help(int command_count,
 		      const char *shortrevisions, const char *shortonto,
 		      struct strbuf *buf);
-int edit_todo_list(struct repository *r, struct todo_list *todo_list,
-		   struct todo_list *new_todo, const char *shortrevisions,
-		   const char *shortonto, unsigned flags);
+int edit_todo_list(struct repository *r, struct replay_opts *opts,
+		   struct todo_list *todo_list, struct todo_list *new_todo,
+		   const char *shortrevisions, const char *shortonto,
+		   unsigned flags);
 
 int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo);
 int todo_list_check_against_backup(struct repository *r,
+				   struct replay_opts *opts,
 				   struct todo_list *todo_list);
 
 #endif
diff --git a/sequencer.c b/sequencer.c
index 2c19846385b..a3154ba3347 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2573,8 +2573,9 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
 	return 0;
 }
 
-static int parse_insn_line(struct repository *r, struct todo_item *item,
-			   const char *buf, const char *bol, char *eol)
+static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
+			   struct todo_item *item, const char *buf,
+			   const char *bol, char *eol)
 {
 	struct object_id commit_oid;
 	char *end_of_object_name;
@@ -2708,8 +2709,8 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
 	return ret;
 }
 
-int todo_list_parse_insn_buffer(struct repository *r, char *buf,
-				struct todo_list *todo_list)
+int todo_list_parse_insn_buffer(struct repository *r, struct replay_opts *opts,
+				char *buf, struct todo_list *todo_list)
 {
 	struct todo_item *item;
 	char *p = buf, *next_p;
@@ -2727,7 +2728,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
 
 		item = append_new_todo(todo_list);
 		item->offset_in_buf = p - todo_list->buf.buf;
-		if (parse_insn_line(r, item, buf, p, eol)) {
+		if (parse_insn_line(r, opts, item, buf, p, eol)) {
 			res = error(_("invalid line %d: %.*s"),
 				i, (int)(eol - p), p);
 			item->command = TODO_COMMENT + 1;
@@ -2875,7 +2876,7 @@ static int read_populate_todo(struct repository *r,
 	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
 		return -1;
 
-	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
+	res = todo_list_parse_insn_buffer(r, opts, todo_list->buf.buf, todo_list);
 	if (res) {
 		if (is_rebase_i(opts))
 			return error(_("please fix this using "
@@ -2905,7 +2906,7 @@ static int read_populate_todo(struct repository *r,
 		struct todo_list done = TODO_LIST_INIT;
 
 		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
-		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
+		    !todo_list_parse_insn_buffer(r, opts, done.buf.buf, &done))
 			todo_list->done_nr = count_commands(&done);
 		else
 			todo_list->done_nr = 0;
@@ -5251,7 +5252,8 @@ int sequencer_continue(struct repository *r, struct replay_opts *opts)
 			goto release_todo_list;
 
 		if (file_exists(rebase_path_dropped())) {
-			if ((res = todo_list_check_against_backup(r, &todo_list)))
+			if ((res = todo_list_check_against_backup(r, opts,
+								  &todo_list)))
 				goto release_todo_list;
 
 			unlink(rebase_path_dropped());
@@ -6294,7 +6296,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
 		return error(_("nothing to do"));
 	}
 
-	res = edit_todo_list(r, todo_list, &new_todo, shortrevisions,
+	res = edit_todo_list(r, opts, todo_list, &new_todo, shortrevisions,
 			     shortonto, flags);
 	if (res == -1)
 		return -1;
@@ -6322,7 +6324,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
 	strbuf_release(&buf2);
 	/* Nothing is done yet, and we're reparsing, so let's reset the count */
 	new_todo.total_nr = 0;
-	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
+	if (todo_list_parse_insn_buffer(r, opts, new_todo.buf.buf, &new_todo) < 0)
 		BUG("invalid todo list after expanding IDs:\n%s",
 		    new_todo.buf.buf);
 
diff --git a/sequencer.h b/sequencer.h
index 437eabd38af..33943e5ed28 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -137,8 +137,8 @@ struct todo_list {
 	.buf = STRBUF_INIT, \
 }
 
-int todo_list_parse_insn_buffer(struct repository *r, char *buf,
-				struct todo_list *todo_list);
+int todo_list_parse_insn_buffer(struct repository *r, struct replay_opts *opts,
+				char *buf, struct todo_list *todo_list);
 int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
 			    const char *file, const char *shortrevisions,
 			    const char *shortonto, int num, unsigned flags);
-- 
gitgitgadget

[PATCH v2 2/2] rebase -i: improve error message when picking merge

[Phillip Wood via GitGitGadget]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

The only todo commands that accept a merge commit are "merge" and
"reset". All the other commands like "pick" or "reword" fail when they
try to pick a a merge commit and print the message

    error: commit abc123 is a merge but no -m option was given.

followed by a hint about the command being rescheduled. This message is
designed to help the user when they cherry-pick a merge and forget to
pass "-m". For users who are rebasing the message is confusing as there
is no way for rebase to cherry-pick the merge.

Improve the user experience by detecting the error when the todo list is
parsed rather than waiting for the "pick" command to fail and print a
message recommending the "merge" command instead. We recommend "merge"
rather than "exec git cherry-pick -m ..." on the assumption that
cherry-picking merges is relatively rare and it is more likely that the
user chose "pick" by a mistake.

It would be possible to support cherry-picking merges by allowing the
user to pass "-m" to "pick" commands but that adds complexity to do
something that can already be achieved with

    exec git cherry-pick -m1 abc123

Reported-by: Stefan Haller <lists@haller-berlin.de>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 sequencer.c                   | 37 +++++++++++++++++++++++++++++++++--
 t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index a3154ba3347..4012c6f88d9 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2573,7 +2573,35 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
 	return 0;
 }
 
-static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
+static int error_merge_commit(enum todo_command command)
+{
+	switch(command) {
+	case TODO_PICK:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s'"),
+			     todo_command_info[command].str, "merge -C");
+
+	case TODO_REWORD:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s'"),
+			     todo_command_info[command].str, "merge -c");
+
+	case TODO_EDIT:
+		return error(_("'%s' does not accept merge commits, "
+			       "please use '%s' followed by '%s'"),
+			     todo_command_info[command].str,
+			     "merge -C", "break");
+
+	case TODO_FIXUP:
+	case TODO_SQUASH:
+		return error(_("cannot squash merge commit into another commit"));
+
+	default:
+		BUG("unexpected todo_command");
+	}
+}
+
+static int parse_insn_line(struct repository *r, struct replay_opts *opts,
 			   struct todo_item *item, const char *buf,
 			   const char *bol, char *eol)
 {
@@ -2679,7 +2707,12 @@ static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED
 		return status;
 
 	item->commit = lookup_commit_reference(r, &commit_oid);
-	return item->commit ? 0 : -1;
+	if (!item->commit)
+		return -1;
+	if (is_rebase_i(opts) && item->command != TODO_MERGE &&
+	    item->commit->parents && item->commit->parents->next)
+		return error_merge_commit(item->command);
+	return 0;
 }
 
 int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index d1bead61fad..8565fd4b5ae 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -2215,6 +2215,39 @@ test_expect_success 'bad labels and refs rejected when parsing todo list' '
 	test_path_is_missing execed
 '
 
+test_expect_success 'non-merge commands reject merge commits' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	git checkout E &&
+	git merge I &&
+	oid=$(git rev-parse HEAD) &&
+	cat >todo <<-EOF &&
+	pick $oid
+	reword $oid
+	edit $oid
+	fixup $oid
+	squash $oid
+	EOF
+	(
+		set_replace_editor todo &&
+		test_must_fail git rebase -i HEAD 2>actual
+	) &&
+	cat >expect <<-EOF &&
+	error: ${SQ}pick${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ}
+	error: invalid line 1: pick $oid
+	error: ${SQ}reword${SQ} does not accept merge commits, please use ${SQ}merge -c${SQ}
+	error: invalid line 2: reword $oid
+	error: ${SQ}edit${SQ} does not accept merge commits, please use ${SQ}merge -C${SQ} followed by ${SQ}break${SQ}
+	error: invalid line 3: edit $oid
+	error: cannot squash merge commit into another commit
+	error: invalid line 4: fixup $oid
+	error: cannot squash merge commit into another commit
+	error: invalid line 5: squash $oid
+	You can fix this with ${SQ}git rebase --edit-todo${SQ} and then run ${SQ}git rebase --continue${SQ}.
+	Or you can abort the rebase with ${SQ}git rebase --abort${SQ}.
+	EOF
+	test_cmp expect actual
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged
-- 
gitgitgadget

Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Junio C Hamano]

"Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> The only todo commands that accept a merge commit are "merge" and
> "reset". All the other commands like "pick" or "reword" fail when they
> try to pick a a merge commit and print the message
>
>     error: commit abc123 is a merge but no -m option was given.
>
> followed by a hint about the command being rescheduled. This message is
> designed to help the user when they cherry-pick a merge and forget to
> pass "-m". For users who are rebasing the message is confusing as there
> is no way for rebase to cherry-pick the merge.
>
> Improve the user experience by detecting the error when the todo list is
> parsed rather than waiting for the "pick" command to fail and print a
> message recommending the "merge" command instead. We recommend "merge"
> rather than "exec git cherry-pick -m ..." on the assumption that
> cherry-picking merges is relatively rare and it is more likely that the
> user chose "pick" by a mistake.

Now, the mention of "all the other commands" makes me curious what
should happen when your "squash" and "fixup" named a merge commit.
I think it should just error out without any recourse, but it is
more than likely that I am missing some use cases where it is useful
to "squash" or "fixup" a merge commit on top of an existing commit?

> It would be possible to support cherry-picking merges by allowing the
> user to pass "-m" to "pick" commands but that adds complexity to do
> something that can already be achieved with
>
>     exec git cherry-pick -m1 abc123

I have no strong opinions between this and "merge" for "pick",
"edit", and "reword".

> Reported-by: Stefan Haller <lists@haller-berlin.de>
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---
>  sequencer.c                   | 37 +++++++++++++++++++++++++++++++++--
>  t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+), 2 deletions(-)

So, having thought about my version of a solution from the problem
description above without looking at your answers, let's see how you
solved it.

> diff --git a/sequencer.c b/sequencer.c
> index a3154ba3347..4012c6f88d9 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -2573,7 +2573,35 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
>  	return 0;
>  }
>  
> -static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
> +static int error_merge_commit(enum todo_command command)
> +{
> +	switch(command) {
> +	case TODO_PICK:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -C");
> +
> +	case TODO_REWORD:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s'"),
> +			     todo_command_info[command].str, "merge -c");
> +
> +	case TODO_EDIT:
> +		return error(_("'%s' does not accept merge commits, "
> +			       "please use '%s' followed by '%s'"),
> +			     todo_command_info[command].str,
> +			     "merge -C", "break");

OK.  And when hitting the "break", they know that they are supposed
to say "git commit --amend" and then "git rebase --continue"?

> +	case TODO_FIXUP:
> +	case TODO_SQUASH:
> +		return error(_("cannot squash merge commit into another commit"));

OK, this is as I expected.

> +	default:
> +		BUG("unexpected todo_command");
> +	}
> +}
> +
> +static int parse_insn_line(struct repository *r, struct replay_opts *opts,
>  			   struct todo_item *item, const char *buf,
>  			   const char *bol, char *eol)
>  {
> @@ -2679,7 +2707,12 @@ static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED
>  		return status;
>  
>  	item->commit = lookup_commit_reference(r, &commit_oid);
> -	return item->commit ? 0 : -1;
> +	if (!item->commit)
> +		return -1;
> +	if (is_rebase_i(opts) && item->command != TODO_MERGE &&
> +	    item->commit->parents && item->commit->parents->next)
> +		return error_merge_commit(item->command);

This is good for now, but we may see command other than TODO_MERGE
learn how to handle a merge commit, and when that happens, I wonder
what we want to do here.  One thought is to do this:

	if (is_rebase_i(opts) && is_merge_commit(item->commit))
        	return error_merge_commit(item);

and teach error_merge_commit() to silently return 0 on TODO_MERGE.
Other commands, when they learn how to deal with a merge commit,
will then update their entries in error_merge_commit().

Would we want to customize the message from error_merge_commit() to
make it closer to cut-and-paste ready?  For that, something like

	int error_merge_commit(struct todo_item *item)
	{
		switch (item->command) {
		case TODO_PICK:
			return error(_("'%s'" is bad, plase use "
				       '%s %s'"),
				todo_command_info[item->command].str,
				"merge -C",
				oid_to_hex(item->commit->oid));
		...
		}
	}

might go in a more friendly way.

Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Patrick Steinhardt]

[-- Attachment #1: Type: text/plain, Size: 6422 bytes --]

On Mon, Apr 08, 2024 at 03:29:42PM -0700, Junio C Hamano wrote:
> "Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:
> 
> > From: Phillip Wood <phillip.wood@dunelm.org.uk>
> >
> > The only todo commands that accept a merge commit are "merge" and
> > "reset". All the other commands like "pick" or "reword" fail when they
> > try to pick a a merge commit and print the message
> >
> >     error: commit abc123 is a merge but no -m option was given.
> >
> > followed by a hint about the command being rescheduled. This message is
> > designed to help the user when they cherry-pick a merge and forget to
> > pass "-m". For users who are rebasing the message is confusing as there
> > is no way for rebase to cherry-pick the merge.
> >
> > Improve the user experience by detecting the error when the todo list is
> > parsed rather than waiting for the "pick" command to fail and print a
> > message recommending the "merge" command instead. We recommend "merge"
> > rather than "exec git cherry-pick -m ..." on the assumption that
> > cherry-picking merges is relatively rare and it is more likely that the
> > user chose "pick" by a mistake.
> 
> Now, the mention of "all the other commands" makes me curious what
> should happen when your "squash" and "fixup" named a merge commit.
> I think it should just error out without any recourse, but it is
> more than likely that I am missing some use cases where it is useful
> to "squash" or "fixup" a merge commit on top of an existing commit?
> 
> > It would be possible to support cherry-picking merges by allowing the
> > user to pass "-m" to "pick" commands but that adds complexity to do
> > something that can already be achieved with
> >
> >     exec git cherry-pick -m1 abc123
> 
> I have no strong opinions between this and "merge" for "pick",
> "edit", and "reword".
> 
> > Reported-by: Stefan Haller <lists@haller-berlin.de>
> > Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> > ---
> >  sequencer.c                   | 37 +++++++++++++++++++++++++++++++++--
> >  t/t3404-rebase-interactive.sh | 33 +++++++++++++++++++++++++++++++
> >  2 files changed, 68 insertions(+), 2 deletions(-)
> 
> So, having thought about my version of a solution from the problem
> description above without looking at your answers, let's see how you
> solved it.
> 
> > diff --git a/sequencer.c b/sequencer.c
> > index a3154ba3347..4012c6f88d9 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -2573,7 +2573,35 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
> >  	return 0;
> >  }
> >  
> > -static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
> > +static int error_merge_commit(enum todo_command command)
> > +{
> > +	switch(command) {
> > +	case TODO_PICK:
> > +		return error(_("'%s' does not accept merge commits, "
> > +			       "please use '%s'"),
> > +			     todo_command_info[command].str, "merge -C");
> > +
> > +	case TODO_REWORD:
> > +		return error(_("'%s' does not accept merge commits, "
> > +			       "please use '%s'"),
> > +			     todo_command_info[command].str, "merge -c");
> > +
> > +	case TODO_EDIT:
> > +		return error(_("'%s' does not accept merge commits, "
> > +			       "please use '%s' followed by '%s'"),
> > +			     todo_command_info[command].str,
> > +			     "merge -C", "break");
> 
> OK.  And when hitting the "break", they know that they are supposed
> to say "git commit --amend" and then "git rebase --continue"?
> 
> > +	case TODO_FIXUP:
> > +	case TODO_SQUASH:
> > +		return error(_("cannot squash merge commit into another commit"));
> 
> OK, this is as I expected.
> 
> > +	default:
> > +		BUG("unexpected todo_command");
> > +	}
> > +}
> > +
> > +static int parse_insn_line(struct repository *r, struct replay_opts *opts,
> >  			   struct todo_item *item, const char *buf,
> >  			   const char *bol, char *eol)
> >  {
> > @@ -2679,7 +2707,12 @@ static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED
> >  		return status;
> >  
> >  	item->commit = lookup_commit_reference(r, &commit_oid);
> > -	return item->commit ? 0 : -1;
> > +	if (!item->commit)
> > +		return -1;
> > +	if (is_rebase_i(opts) && item->command != TODO_MERGE &&
> > +	    item->commit->parents && item->commit->parents->next)
> > +		return error_merge_commit(item->command);
> 
> This is good for now, but we may see command other than TODO_MERGE
> learn how to handle a merge commit, and when that happens, I wonder
> what we want to do here.  One thought is to do this:
> 
> 	if (is_rebase_i(opts) && is_merge_commit(item->commit))
>         	return error_merge_commit(item);
> 
> and teach error_merge_commit() to silently return 0 on TODO_MERGE.
> Other commands, when they learn how to deal with a merge commit,
> will then update their entries in error_merge_commit().
> 
> Would we want to customize the message from error_merge_commit() to
> make it closer to cut-and-paste ready?  For that, something like
> 
> 	int error_merge_commit(struct todo_item *item)
> 	{
> 		switch (item->command) {
> 		case TODO_PICK:
> 			return error(_("'%s'" is bad, plase use "
> 				       '%s %s'"),
> 				todo_command_info[item->command].str,
> 				"merge -C",
> 				oid_to_hex(item->commit->oid));
> 		...
> 		}
> 	}
> 
> might go in a more friendly way.

I was asking basically the same thing in [1]. Quoting that part:

> I wonder how actionable these commands are. Can we give the full command
> that the user can use instead, including the commit ID?
> 
> That raises another question though: how exactly is the user supposed to
> perform the merge? Should they merge the merge commit, resulting in two
> merge commits? Should they pick one of the sides, and if so, which one?
> I guess the answer is "it depends", which makes it harder for us to come
> up with actionable advice here.

So I think it's okay to not mention the exact commit here because we
cannot reliably second-guess the ultimate extent. My basic assumption is
that in many cases the user may not even be aware of them trying to pick
a merge commit, and that it may not have been their intent.

I might just as well be wrong about that assumption though.

Patrick

[1]: https://lore.kernel.org/git/Zg5D3dXYFM2SONE-@tanuki/

[-- Attachment #2: signature.asc --]
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Re: [PATCH v2 1/2] rebase -i: pass struct replay_opts to parse_insn_line()

[Patrick Steinhardt]

[-- Attachment #1: Type: text/plain, Size: 11005 bytes --]

On Mon, Apr 08, 2024 at 02:16:26PM +0000, Phillip Wood via GitGitGadget wrote:
> From: Phillip Wood <phillip.wood@dunelm.org.uk>
> 
> This new parameter will be used in the next commit.

Nit: we don't typically write commit messages as a continuation of their
subject. Other than that this commit looks good to me.

Patrick

> As adding the
> parameter requires quite a few changes to plumb it through the call
> chain these are separated into their own commit to avoid cluttering up
> the next commit with incidental changes.
> 
> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> ---
>  builtin/rebase.c     | 17 +++++++++++------
>  rebase-interactive.c | 21 +++++++++++++--------
>  rebase-interactive.h |  9 ++++++---
>  sequencer.c          | 22 ++++++++++++----------
>  sequencer.h          |  4 ++--
>  5 files changed, 44 insertions(+), 29 deletions(-)
> 
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 891f28468e8..a33a2ed413a 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -194,7 +194,7 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
>  	return replay;
>  }
>  
> -static int edit_todo_file(unsigned flags)
> +static int edit_todo_file(unsigned flags, struct replay_opts *opts)
>  {
>  	const char *todo_file = rebase_path_todo();
>  	struct todo_list todo_list = TODO_LIST_INIT,
> @@ -205,7 +205,8 @@ static int edit_todo_file(unsigned flags)
>  		return error_errno(_("could not read '%s'."), todo_file);
>  
>  	strbuf_stripspace(&todo_list.buf, comment_line_str);
> -	res = edit_todo_list(the_repository, &todo_list, &new_todo, NULL, NULL, flags);
> +	res = edit_todo_list(the_repository, opts, &todo_list, &new_todo,
> +			     NULL, NULL, flags);
>  	if (!res && todo_list_write_to_file(the_repository, &new_todo, todo_file,
>  					    NULL, NULL, -1, flags & ~(TODO_LIST_SHORTEN_IDS)))
>  		res = error_errno(_("could not write '%s'"), todo_file);
> @@ -296,8 +297,8 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
>  		error(_("could not generate todo list"));
>  	else {
>  		discard_index(&the_index);
> -		if (todo_list_parse_insn_buffer(the_repository, todo_list.buf.buf,
> -						&todo_list))
> +		if (todo_list_parse_insn_buffer(the_repository, &replay,
> +						todo_list.buf.buf, &todo_list))
>  			BUG("unusable todo list");
>  
>  		ret = complete_action(the_repository, &replay, flags,
> @@ -352,9 +353,13 @@ static int run_sequencer_rebase(struct rebase_options *opts)
>  		replay_opts_release(&replay_opts);
>  		break;
>  	}
> -	case ACTION_EDIT_TODO:
> -		ret = edit_todo_file(flags);
> +	case ACTION_EDIT_TODO: {
> +		struct replay_opts replay_opts = get_replay_opts(opts);
> +
> +		ret = edit_todo_file(flags, &replay_opts);
> +		replay_opts_release(&replay_opts);
>  		break;
> +	}
>  	case ACTION_SHOW_CURRENT_PATCH: {
>  		struct child_process cmd = CHILD_PROCESS_INIT;
>  
> diff --git a/rebase-interactive.c b/rebase-interactive.c
> index c343e16fcdd..56fd7206a95 100644
> --- a/rebase-interactive.c
> +++ b/rebase-interactive.c
> @@ -101,9 +101,10 @@ void append_todo_help(int command_count,
>  	strbuf_add_commented_lines(buf, msg, strlen(msg), comment_line_str);
>  }
>  
> -int edit_todo_list(struct repository *r, struct todo_list *todo_list,
> -		   struct todo_list *new_todo, const char *shortrevisions,
> -		   const char *shortonto, unsigned flags)
> +int edit_todo_list(struct repository *r, struct replay_opts *opts,
> +		   struct todo_list *todo_list, struct todo_list *new_todo,
> +		   const char *shortrevisions, const char *shortonto,
> +		   unsigned flags)
>  {
>  	const char *todo_file = rebase_path_todo(),
>  		*todo_backup = rebase_path_todo_backup();
> @@ -114,7 +115,9 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>  	 * it.  If there is an error, we do not return, because the user
>  	 * might want to fix it in the first place. */
>  	if (!initial)
> -		incorrect = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list) |
> +		incorrect = todo_list_parse_insn_buffer(r, opts,
> +							todo_list->buf.buf,
> +							todo_list) |
>  			file_exists(rebase_path_dropped());
>  
>  	if (todo_list_write_to_file(r, todo_list, todo_file, shortrevisions, shortonto,
> @@ -134,13 +137,13 @@ int edit_todo_list(struct repository *r, struct todo_list *todo_list,
>  	if (initial && new_todo->buf.len == 0)
>  		return -3;
>  
> -	if (todo_list_parse_insn_buffer(r, new_todo->buf.buf, new_todo)) {
> +	if (todo_list_parse_insn_buffer(r, opts, new_todo->buf.buf, new_todo)) {
>  		fprintf(stderr, _(edit_todo_list_advice));
>  		return -4;
>  	}
>  
>  	if (incorrect) {
> -		if (todo_list_check_against_backup(r, new_todo)) {
> +		if (todo_list_check_against_backup(r, opts, new_todo)) {
>  			write_file(rebase_path_dropped(), "%s", "");
>  			return -4;
>  		}
> @@ -228,13 +231,15 @@ int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo)
>  	return res;
>  }
>  
> -int todo_list_check_against_backup(struct repository *r, struct todo_list *todo_list)
> +int todo_list_check_against_backup(struct repository *r,
> +				   struct replay_opts *opts,
> +				   struct todo_list *todo_list)
>  {
>  	struct todo_list backup = TODO_LIST_INIT;
>  	int res = 0;
>  
>  	if (strbuf_read_file(&backup.buf, rebase_path_todo_backup(), 0) > 0) {
> -		todo_list_parse_insn_buffer(r, backup.buf.buf, &backup);
> +		todo_list_parse_insn_buffer(r, opts, backup.buf.buf, &backup);
>  		res = todo_list_check(&backup, todo_list);
>  	}
>  
> diff --git a/rebase-interactive.h b/rebase-interactive.h
> index 7239c60f791..8e5b181b334 100644
> --- a/rebase-interactive.h
> +++ b/rebase-interactive.h
> @@ -3,17 +3,20 @@
>  
>  struct strbuf;
>  struct repository;
> +struct replay_opts;
>  struct todo_list;
>  
>  void append_todo_help(int command_count,
>  		      const char *shortrevisions, const char *shortonto,
>  		      struct strbuf *buf);
> -int edit_todo_list(struct repository *r, struct todo_list *todo_list,
> -		   struct todo_list *new_todo, const char *shortrevisions,
> -		   const char *shortonto, unsigned flags);
> +int edit_todo_list(struct repository *r, struct replay_opts *opts,
> +		   struct todo_list *todo_list, struct todo_list *new_todo,
> +		   const char *shortrevisions, const char *shortonto,
> +		   unsigned flags);
>  
>  int todo_list_check(struct todo_list *old_todo, struct todo_list *new_todo);
>  int todo_list_check_against_backup(struct repository *r,
> +				   struct replay_opts *opts,
>  				   struct todo_list *todo_list);
>  
>  #endif
> diff --git a/sequencer.c b/sequencer.c
> index 2c19846385b..a3154ba3347 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -2573,8 +2573,9 @@ static int check_label_or_ref_arg(enum todo_command command, const char *arg)
>  	return 0;
>  }
>  
> -static int parse_insn_line(struct repository *r, struct todo_item *item,
> -			   const char *buf, const char *bol, char *eol)
> +static int parse_insn_line(struct repository *r, struct replay_opts *opts UNUSED,
> +			   struct todo_item *item, const char *buf,
> +			   const char *bol, char *eol)
>  {
>  	struct object_id commit_oid;
>  	char *end_of_object_name;
> @@ -2708,8 +2709,8 @@ int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *
>  	return ret;
>  }
>  
> -int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list)
> +int todo_list_parse_insn_buffer(struct repository *r, struct replay_opts *opts,
> +				char *buf, struct todo_list *todo_list)
>  {
>  	struct todo_item *item;
>  	char *p = buf, *next_p;
> @@ -2727,7 +2728,7 @@ int todo_list_parse_insn_buffer(struct repository *r, char *buf,
>  
>  		item = append_new_todo(todo_list);
>  		item->offset_in_buf = p - todo_list->buf.buf;
> -		if (parse_insn_line(r, item, buf, p, eol)) {
> +		if (parse_insn_line(r, opts, item, buf, p, eol)) {
>  			res = error(_("invalid line %d: %.*s"),
>  				i, (int)(eol - p), p);
>  			item->command = TODO_COMMENT + 1;
> @@ -2875,7 +2876,7 @@ static int read_populate_todo(struct repository *r,
>  	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
>  		return -1;
>  
> -	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
> +	res = todo_list_parse_insn_buffer(r, opts, todo_list->buf.buf, todo_list);
>  	if (res) {
>  		if (is_rebase_i(opts))
>  			return error(_("please fix this using "
> @@ -2905,7 +2906,7 @@ static int read_populate_todo(struct repository *r,
>  		struct todo_list done = TODO_LIST_INIT;
>  
>  		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
> -		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
> +		    !todo_list_parse_insn_buffer(r, opts, done.buf.buf, &done))
>  			todo_list->done_nr = count_commands(&done);
>  		else
>  			todo_list->done_nr = 0;
> @@ -5251,7 +5252,8 @@ int sequencer_continue(struct repository *r, struct replay_opts *opts)
>  			goto release_todo_list;
>  
>  		if (file_exists(rebase_path_dropped())) {
> -			if ((res = todo_list_check_against_backup(r, &todo_list)))
> +			if ((res = todo_list_check_against_backup(r, opts,
> +								  &todo_list)))
>  				goto release_todo_list;
>  
>  			unlink(rebase_path_dropped());
> @@ -6294,7 +6296,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>  		return error(_("nothing to do"));
>  	}
>  
> -	res = edit_todo_list(r, todo_list, &new_todo, shortrevisions,
> +	res = edit_todo_list(r, opts, todo_list, &new_todo, shortrevisions,
>  			     shortonto, flags);
>  	if (res == -1)
>  		return -1;
> @@ -6322,7 +6324,7 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
>  	strbuf_release(&buf2);
>  	/* Nothing is done yet, and we're reparsing, so let's reset the count */
>  	new_todo.total_nr = 0;
> -	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) < 0)
> +	if (todo_list_parse_insn_buffer(r, opts, new_todo.buf.buf, &new_todo) < 0)
>  		BUG("invalid todo list after expanding IDs:\n%s",
>  		    new_todo.buf.buf);
>  
> diff --git a/sequencer.h b/sequencer.h
> index 437eabd38af..33943e5ed28 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -137,8 +137,8 @@ struct todo_list {
>  	.buf = STRBUF_INIT, \
>  }
>  
> -int todo_list_parse_insn_buffer(struct repository *r, char *buf,
> -				struct todo_list *todo_list);
> +int todo_list_parse_insn_buffer(struct repository *r, struct replay_opts *opts,
> +				char *buf, struct todo_list *todo_list);
>  int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
>  			    const char *file, const char *shortrevisions,
>  			    const char *shortonto, int num, unsigned flags);
> -- 
> gitgitgadget
> 

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Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Junio C Hamano]

Patrick Steinhardt <ps@pks.im> writes:

> So I think it's okay to not mention the exact commit here because we
> cannot reliably second-guess the ultimate extent. My basic assumption is
> that in many cases the user may not even be aware of them trying to pick
> a merge commit, and that it may not have been their intent.

Hmph, if that assumption is really true, would suggesting "merge -C"
be the right thing in the first place?

I do not deal with non-linear stuff in "rebase -i" or sequencer, so
I may not be a good person to judge how good your basic assumption
is, though.

Thanks.

Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Patrick Steinhardt]

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On Mon, Apr 08, 2024 at 10:08:24PM -0700, Junio C Hamano wrote:
> Patrick Steinhardt <ps@pks.im> writes:
> 
> > So I think it's okay to not mention the exact commit here because we
> > cannot reliably second-guess the ultimate extent. My basic assumption is
> > that in many cases the user may not even be aware of them trying to pick
> > a merge commit, and that it may not have been their intent.
> 
> Hmph, if that assumption is really true, would suggesting "merge -C"
> be the right thing in the first place?
> 
> I do not deal with non-linear stuff in "rebase -i" or sequencer, so
> I may not be a good person to judge how good your basic assumption
> is, though.

Yeah, neither do I. The assumption really only comes from my own gut
feeling, which can certainly be quite wrong.

Patrick

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Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Phillip Wood]

Hi Junio

On 08/04/2024 23:29, Junio C Hamano wrote:
> "Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:
>> +	case TODO_EDIT:
>> +		return error(_("'%s' does not accept merge commits, "
>> +			       "please use '%s' followed by '%s'"),
>> +			     todo_command_info[command].str,
>> +			     "merge -C", "break");
> 
> OK.  And when hitting the "break", they know that they are supposed
> to say "git commit --amend" and then "git rebase --continue"?

Yes. I guess we could add a hint to that effect if you think its worth it.

>>   	item->commit = lookup_commit_reference(r, &commit_oid);
>> -	return item->commit ? 0 : -1;
>> +	if (!item->commit)
>> +		return -1;
>> +	if (is_rebase_i(opts) && item->command != TODO_MERGE &&
>> +	    item->commit->parents && item->commit->parents->next)
>> +		return error_merge_commit(item->command);
> 
> This is good for now, but we may see command other than TODO_MERGE
> learn how to handle a merge commit, and when that happens, I wonder
> what we want to do here.  One thought is to do this:
> 
> 	if (is_rebase_i(opts) && is_merge_commit(item->commit))
>          	return error_merge_commit(item);
> 
> and teach error_merge_commit() to silently return 0 on TODO_MERGE.
> Other commands, when they learn how to deal with a merge commit,
> will then update their entries in error_merge_commit().
f
It feels funny to call error_merge_commit() for a command that we know 
supports merges but I can see that would make it easier to extend in the 
future.

> Would we want to customize the message from error_merge_commit() to
> make it closer to cut-and-paste ready?  For that, something like
> 
> 	int error_merge_commit(struct todo_item *item)
> 	{
> 		switch (item->command) {
> 		case TODO_PICK:
> 			return error(_("'%s'" is bad, plase use "
> 				       '%s %s'"),
> 				todo_command_info[item->command].str,
> 				"merge -C",
> 				oid_to_hex(item->commit->oid));
> 		...
> 		}
> 	}
> 
> might go in a more friendly way.

If we want something the user can cut and paste then we would need to 
suggest a second parent for the merge. We cannot just use the existing 
parent as it may be rebased which means tracking all the commits we see 
while parsing the list. If the second parent is rebased we need to make 
sure the user labels it so we can use that label here. For that reason 
(and the fact that I don't think can we really tell what the user was 
hoping to achieve) I think the best we can do is point the user in the 
direction of the "merge" command even though that leaves them to figure 
out what to do with that command.

Best Wishes

Phillip

Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Junio C Hamano]

Phillip Wood <phillip.wood123@gmail.com> writes:

>>> +		return error(_("'%s' does not accept merge commits, "
>>> +			       "please use '%s' followed by '%s'"),
>>> +			     todo_command_info[command].str,
>>> +			     "merge -C", "break");
>> OK.  And when hitting the "break", they know that they are supposed
>> to say "git commit --amend" and then "git rebase --continue"?
>
> Yes. I guess we could add a hint to that effect if you think its worth it.

As I said elsewhere, I do not deal with non-linear stuff using
sequencer, so I _may_ be missing something obvious to the target
audience of this message.  But if I were dipping my toes to try
mucking with sequencer and edit the todo myself by inserting a random
merge commit there and got this message, I would have probably
appreciated if the message were a bit more explicit _why_ I would
want to use the 'break' there.  Otherwise, I probably would be lost
sitting in front of the shell command prompt.  If it were

	'pick' does not take a merge commit.  If you wanted to
	replay the merge, use 'merge -C' on the commit, and then
	'break' to give the control back to you so that you can
	do 'git commit --amend && git rebase --continue'.

that would have given me 70% of what I needed (the other 30% is why
I would want to "--amend", instead of just taking the result of
'merge -C' as-is, though).

We can formulate the message in such a way that a succinct first
part is sufficient for people who know the command, while the latter
more verbose and prescriptive part can be hidden behind the advice
mechanism.

> It feels funny to call error_merge_commit() for a command that we know
> supports merges but I can see that would make it easier to extend in
> the future.

Yes, I think that it is just a sign that the function is misnamed.
"Gee we have a merge commit, please tell me what you want to do with
it" is what the caller is asking, and the error messages are side
effects the caller does not have to care too much about.

Re: [PATCH v2 2/2] rebase -i: improve error message when picking merge

[Phillip Wood]

Hi Junio

On 09/04/2024 20:56, Junio C Hamano wrote:
> Phillip Wood <phillip.wood123@gmail.com> writes:
> 
>>>> +		return error(_("'%s' does not accept merge commits, "
>>>> +			       "please use '%s' followed by '%s'"),
>>>> +			     todo_command_info[command].str,
>>>> +			     "merge -C", "break");
>>> OK.  And when hitting the "break", they know that they are supposed
>>> to say "git commit --amend" and then "git rebase --continue"?
>>
>> Yes. I guess we could add a hint to that effect if you think its worth it.
> 
> As I said elsewhere, I do not deal with non-linear stuff using
> sequencer, so I _may_ be missing something obvious to the target
> audience of this message.  But if I were dipping my toes to try
> mucking with sequencer and edit the todo myself by inserting a random
> merge commit there and got this message, I would have probably
> appreciated if the message were a bit more explicit _why_ I would
> want to use the 'break' there.  Otherwise, I probably would be lost
> sitting in front of the shell command prompt.  If it were
> 
> 	'pick' does not take a merge commit.  If you wanted to
> 	replay the merge, use 'merge -C' on the commit, and then
> 	'break' to give the control back to you so that you can
> 	do 'git commit --amend && git rebase --continue'.
> 
> that would have given me 70% of what I needed (the other 30% is why
> I would want to "--amend", instead of just taking the result of
> 'merge -C' as-is, though).
> 
> We can formulate the message in such a way that a succinct first
> part is sufficient for people who know the command, while the latter
> more verbose and prescriptive part can be hidden behind the advice
> mechanism.

I'll re-roll with a short error message plus some advice. I'll have a 
think about adding advice for the other commands as well explaining how 
the "merge" command should be used as well.

>> It feels funny to call error_merge_commit() for a command that we know
>> supports merges but I can see that would make it easier to extend in
>> the future.
> 
> Yes, I think that it is just a sign that the function is misnamed.
> "Gee we have a merge commit, please tell me what you want to do with
> it" is what the caller is asking, and the error messages are side
> effects the caller does not have to care too much about.

Sure

Thanks

Phillip