[PATCH 0/2] rebase --autosquash: handle manual "final fixups"

[PATCH 0/2] rebase --autosquash: handle manual "final fixups"

[Johannes Schindelin via GitGitGadget]

'tis bug fix season! I admit, though, that this bug might be a bit too off
the trodden path to merit fast-tracking into v2.19.0.

While pairing with Jameson Miller to rebase Git for Windows to v2.19.0-rc1,
we had to fix a couple of commits which had somehow lost their proper
authorship (probably due to long fixed bugs in the interactive rebase). We
did so by using empty squash! commits as reminders, so that we could
interrupt the rebase by deleting the squash message, amend the commit
appropriately, and then continue.

This exposed an (admittedly obscure) bug in the interactive rebase: when the
last fixup or squash of a fixup/squash chain is aborted, and then the HEAD
commit is amended, the rebase would not forget about the fixup/squash chain.
It would hold onto the information about the current fixup count and the
intermediate commit message. And upon processing another fixup/squash chain,
that information would be reused!

This patch pair first introduces the test case to confirm the breakage, and
then fixes it in the minimal way.

Johannes Schindelin (2):
  rebase -i --autosquash: demonstrate a problem skipping the last squash
  rebase -i: be careful to wrap up fixup/squash chains

 sequencer.c                  | 17 ++++++++++++++---
 t/t3415-rebase-autosquash.sh | 19 +++++++++++++++++++
 2 files changed, 33 insertions(+), 3 deletions(-)


base-commit: 2f743933341f276111103550fbf383a34dfcfd38
Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-30%2Fdscho%2Frebase-abort-last-squash-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-30/dscho/rebase-abort-last-squash-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/30
-- 
gitgitgadget

[PATCH 1/2] rebase -i --autosquash: demonstrate a problem skipping the last squash

[Johannes Schindelin via GitGitGadget]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

The `git commit --squash` command can be used not only to amend commit
messages and changes, but also to record notes for an upcoming rebase.

For example, when the author information of a given commit is incorrect,
a user might call `git commit --allow-empty -m "Fix author" --squash
<commit>`, to remind them to fix that during the rebase. When the editor
would pop up, the user would simply delete the commit message to abort
the rebase at this stage, fix the author information, and continue with
`git rebase --skip`. (This is a real-world example from the rebase of
Git for Windows onto v2.19.0-rc1.)

However, there is a bug in `git rebase` that will cause the squash
message *not* to be forgotten in this case. It will therefore be reused
in the next fixup/squash chain (if any).

This patch adds a test case to demonstrate this breakage.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/t3415-rebase-autosquash.sh | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
index e364c12622..7d5ea340b3 100755
--- a/t/t3415-rebase-autosquash.sh
+++ b/t/t3415-rebase-autosquash.sh
@@ -330,4 +330,23 @@ test_expect_success 'wrapped original subject' '
 	test $base = $parent
 '
 
+test_expect_failure 'abort last squash' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	test_when_finished "git checkout master" &&
+
+	git checkout -b some-squashes &&
+	git commit --allow-empty -m first &&
+	git commit --allow-empty --squash HEAD &&
+	git commit --allow-empty -m second &&
+	git commit --allow-empty --squash HEAD &&
+
+	test_must_fail git -c core.editor="grep -q ^pick" \
+		rebase -ki --autosquash HEAD~4 &&
+	: do not finish the squash, but resolve it manually &&
+	git commit --allow-empty --amend -m edited-first &&
+	git rebase --skip &&
+	git show >actual &&
+	! grep first actual
+'
+
 test_done
-- 
gitgitgadget

Re*: [PATCH 1/2] rebase -i --autosquash: demonstrate a problem skipping the last squash

[Junio C Hamano]

"Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
writes:

> +	test_must_fail git -c core.editor="grep -q ^pick" \
> +		rebase -ki --autosquash HEAD~4 &&

When merged to 'pu', this reveals that "git rebase" rewritten in C
knows "--keep-empty" but not "-k".

I did a quick eyeballing between master:git-rebase.sh and
pu:builtin/rebase.c and I think that it is the only one that is
missed, but somebody may want to lend us a second set of eyes.

-- >8 --
Subject: rebase: re-add forgotten -k that stands for --keep-empty

630a70ea ("builtin rebase: support `keep-empty` option", 2018-08-08)
forgot that the option comes with a short-and-sweet -k synonym.  Add
it back.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/rebase.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 87590047b3..b26f9c10cf 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -847,7 +847,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			 &options.allow_rerere_autoupdate,
 			 N_("allow rerere to update index  with resolved "
 			    "conflict")),
-		OPT_BOOL(0, "keep-empty", &options.keep_empty,
+		OPT_BOOL('k', "keep-empty", &options.keep_empty,
 			 N_("preserve empty commits during rebase")),
 		OPT_BOOL(0, "autosquash", &options.autosquash,
 			 N_("move commits that begin with "

Re: Re*: [PATCH 1/2] rebase -i --autosquash: demonstrate a problem skipping the last squash

[Johannes Schindelin]

Hi Junio,

On Tue, 4 Sep 2018, Junio C Hamano wrote:

> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
> writes:
> 
> > +	test_must_fail git -c core.editor="grep -q ^pick" \
> > +		rebase -ki --autosquash HEAD~4 &&
> 
> When merged to 'pu', this reveals that "git rebase" rewritten in C
> knows "--keep-empty" but not "-k".

I had already reported this:

https://public-inbox.org/git/nycvar.QRO.7.76.6.1808241803100.73@tvgsbejvaqbjf.bet/

> 
> I did a quick eyeballing between master:git-rebase.sh and
> pu:builtin/rebase.c and I think that it is the only one that is
> missed, but somebody may want to lend us a second set of eyes.
> 
> -- >8 --
> Subject: rebase: re-add forgotten -k that stands for --keep-empty
> 
> 630a70ea ("builtin rebase: support `keep-empty` option", 2018-08-08)
> forgot that the option comes with a short-and-sweet -k synonym.  Add
> it back.
> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Since this is not in `next` yet, let's do it the correct way. I had a
fixup! sitting in my wip-rebase branch all the time, I just needed to find
the time and motivation to figure out how to let GitGitGadget send a v2
when v1 was not sent via GitGitGadget.

Ciao,
Dscho

> ---
>  builtin/rebase.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 87590047b3..b26f9c10cf 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -847,7 +847,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>  			 &options.allow_rerere_autoupdate,
>  			 N_("allow rerere to update index  with resolved "
>  			    "conflict")),
> -		OPT_BOOL(0, "keep-empty", &options.keep_empty,
> +		OPT_BOOL('k', "keep-empty", &options.keep_empty,
>  			 N_("preserve empty commits during rebase")),
>  		OPT_BOOL(0, "autosquash", &options.autosquash,
>  			 N_("move commits that begin with "
> 
> 

Re: Re*: [PATCH 1/2] rebase -i --autosquash: demonstrate a problem skipping the last squash

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> On Tue, 4 Sep 2018, Junio C Hamano wrote:
>
>> "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
>> writes:
>> 
>> > +	test_must_fail git -c core.editor="grep -q ^pick" \
>> > +		rebase -ki --autosquash HEAD~4 &&
>> 
>> When merged to 'pu', this reveals that "git rebase" rewritten in C
>> knows "--keep-empty" but not "-k".
>
> I had already reported this:
>
> https://public-inbox.org/git/nycvar.QRO.7.76.6.1808241803100.73@tvgsbejvaqbjf.bet/

Good that you said there that you'll have it fixed in future updates.

I do not want to leave the project state with failing test at the
tip of 'pu', and I do not want to get distracted in squashing the
fix deep in large sequences of topics that we know will be rerolled
once the prerelease freeze is over anyway, so in the meantime I'll
queue this near the tip of 'pu' to keep the tree sane.

Thanks for eyeballing.

[PATCH 2/2] rebase -i: be careful to wrap up fixup/squash chains

[Johannes Schindelin via GitGitGadget]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

When an interactive rebase was stopped at the end of a fixup/squash
chain, the user might have edited the commit manually before continuing
(with either `git rebase --skip` or `git rebase --continue`, it does not
really matter which).

We need to be very careful to wrap up the fixup/squash chain also in
this scenario: otherwise the next fixup/squash chain would try to pick
up where the previous one was left.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 sequencer.c                  | 17 ++++++++++++++---
 t/t3415-rebase-autosquash.sh |  2 +-
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 84bf598c3e..ac5c805c14 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3578,9 +3578,20 @@ static int commit_staged_changes(struct replay_opts *opts,
 		 * the commit message and if there was a squash, let the user
 		 * edit it.
 		 */
-		if (is_clean && !oidcmp(&head, &to_amend) &&
-		    opts->current_fixup_count > 0 &&
-		    file_exists(rebase_path_stopped_sha())) {
+		if (!is_clean || !opts->current_fixup_count)
+			; /* this is not the final fixup */
+		else if (oidcmp(&head, &to_amend) ||
+			 !file_exists(rebase_path_stopped_sha())) {
+			/* was a final fixup or squash done manually? */
+			if (!is_fixup(peek_command(todo_list, 0))) {
+				unlink(rebase_path_fixup_msg());
+				unlink(rebase_path_squash_msg());
+				unlink(rebase_path_current_fixups());
+				strbuf_reset(&opts->current_fixups);
+				opts->current_fixup_count = 0;
+			}
+		} else {
+			/* we are in a fixup/squash chain */
 			const char *p = opts->current_fixups.buf;
 			int len = opts->current_fixups.len;
 
diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
index 7d5ea340b3..13f5688135 100755
--- a/t/t3415-rebase-autosquash.sh
+++ b/t/t3415-rebase-autosquash.sh
@@ -330,7 +330,7 @@ test_expect_success 'wrapped original subject' '
 	test $base = $parent
 '
 
-test_expect_failure 'abort last squash' '
+test_expect_success 'abort last squash' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	test_when_finished "git checkout master" &&
 
-- 
gitgitgadget

Re: [PATCH 2/2] rebase -i: be careful to wrap up fixup/squash chains

[Junio C Hamano]

> diff --git a/sequencer.c b/sequencer.c
> index 84bf598c3e..ac5c805c14 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -3578,9 +3578,20 @@ static int commit_staged_changes(struct replay_opts *opts,
>  		 * the commit message and if there was a squash, let the user
>  		 * edit it.
>  		 */
> -		if (is_clean && !oidcmp(&head, &to_amend) &&
> -		    opts->current_fixup_count > 0 &&
> -		    file_exists(rebase_path_stopped_sha())) {
> +		if (!is_clean || !opts->current_fixup_count)
> +			; /* this is not the final fixup */
> +		else if (oidcmp(&head, &to_amend) ||
> +			 !file_exists(rebase_path_stopped_sha())) {
> +			/* was a final fixup or squash done manually? */
> +			if (!is_fixup(peek_command(todo_list, 0))) {
> +				unlink(rebase_path_fixup_msg());
> +				unlink(rebase_path_squash_msg());
> +				unlink(rebase_path_current_fixups());
> +				strbuf_reset(&opts->current_fixups);
> +				opts->current_fixup_count = 0;
> +			}

Let me see if the code is easily grokkable by (trying to) follow
aloud.

    We used to refrain from going into this big else clause that
    does the fixup-squash handling when is_clean is false,
    current-count is not yet zero, head and to-amend are different
    commits or stopped-sha file is missing.  The updated code still
    refrains from going into the big else clause under exactly the
    same condition, but it learned to clean up the state, when the
    _next_ one is not a fix-up, i.e. when we are looking at the last
    fixup/squash in the current chain.  And the lack of clean-up
    would have resulted in the next step misbehaving.

I see a few calls to is_fixup(peek_command()) and a local boolean
variable final_fixup used in this function.  I have to wonder if it
makes the resulting code, especially the above part, easier to
follow and understand, if the function peeked todo-list to check if
we are dealing with the final fix-up in a chain very early just
once, and used it to see "are we doing the final fixup/squash in the
current chain?" throughout the rest of the function.

	Side note: I actually think that the existing final_fixup
	boolean means something different (iow, final_fixup is not
	set inside the new "clean-up" code above, even though we
	dealt with the last one in the fix-up chain, and that is not
	a bug---which means that "final_fixup" does not mean "we are
	dealing with the last one in the fix-up chain"), which may
	want to be clarified a bit with in-code comment near where
	the variable is defined for the function to be readable.

In any case, thanks for fixing this, which seems to have appeared in
Git 2.18.  Let's fork a topic from maint, cook it in 'next' and aim
for eventually merging it down for both 2.19 and 2.18 tracks.

> +		} else {
> +			/* we are in a fixup/squash chain */
>  			const char *p = opts->current_fixups.buf;
>  			int len = opts->current_fixups.len;
>  
> diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
> index 7d5ea340b3..13f5688135 100755
> --- a/t/t3415-rebase-autosquash.sh
> +++ b/t/t3415-rebase-autosquash.sh
> @@ -330,7 +330,7 @@ test_expect_success 'wrapped original subject' '
>  	test $base = $parent
>  '
>  
> -test_expect_failure 'abort last squash' '
> +test_expect_success 'abort last squash' '
>  	test_when_finished "test_might_fail git rebase --abort" &&
>  	test_when_finished "git checkout master" &&

Re: [PATCH 2/2] rebase -i: be careful to wrap up fixup/squash chains

[Johannes Schindelin]

Hi Junio,

On Tue, 4 Sep 2018, Junio C Hamano wrote:

> > diff --git a/sequencer.c b/sequencer.c
> > index 84bf598c3e..ac5c805c14 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -3578,9 +3578,20 @@ static int commit_staged_changes(struct replay_opts *opts,
> >  		 * the commit message and if there was a squash, let the user
> >  		 * edit it.
> >  		 */
> > -		if (is_clean && !oidcmp(&head, &to_amend) &&
> > -		    opts->current_fixup_count > 0 &&
> > -		    file_exists(rebase_path_stopped_sha())) {
> > +		if (!is_clean || !opts->current_fixup_count)
> > +			; /* this is not the final fixup */
> > +		else if (oidcmp(&head, &to_amend) ||
> > +			 !file_exists(rebase_path_stopped_sha())) {
> > +			/* was a final fixup or squash done manually? */
> > +			if (!is_fixup(peek_command(todo_list, 0))) {
> > +				unlink(rebase_path_fixup_msg());
> > +				unlink(rebase_path_squash_msg());
> > +				unlink(rebase_path_current_fixups());
> > +				strbuf_reset(&opts->current_fixups);
> > +				opts->current_fixup_count = 0;
> > +			}
> 
> Let me see if the code is easily grokkable by (trying to) follow
> aloud.
> 
>     We used to refrain from going into this big else clause that
>     does the fixup-squash handling when is_clean is false,
>     current-count is not yet zero, head and to-amend are different

s/not yet zero/still zero/

>     commits or stopped-sha file is missing.  The updated code still
>     refrains from going into the big else clause under exactly the
>     same condition, but it learned to clean up the state, when the
>     _next_ one is not a fix-up, i.e. when we are looking at the last
>     fixup/squash in the current chain.  And the lack of clean-up
>     would have resulted in the next step misbehaving.

s/next step/ next fixup or squash chain, if any,/

You got the gist right.

> I see a few calls to is_fixup(peek_command()) and a local boolean
> variable final_fixup used in this function.  I have to wonder if it
> makes the resulting code, especially the above part, easier to
> follow and understand, if the function peeked todo-list to check if
> we are dealing with the final fix-up in a chain very early just
> once, and used it to see "are we doing the final fixup/squash in the
> current chain?" throughout the rest of the function.
> 
> 	Side note: I actually think that the existing final_fixup
> 	boolean means something different (iow, final_fixup is not
> 	set inside the new "clean-up" code above, even though we
> 	dealt with the last one in the fix-up chain, and that is not
> 	a bug---which means that "final_fixup" does not mean "we are
> 	dealing with the last one in the fix-up chain"), which may
> 	want to be clarified a bit with in-code comment near where
> 	the variable is defined for the function to be readable.

Indeed. The `final_fixup` name tries to convey "need to finalize the final
fixup", as in: show the commit message in an editor if any squash! commits
were included, and otherwise simply clean the commit message of all those
commented-out lines.

So that's very different from "is the previously-run todo command a final
fixup in a fixup/squash chain?"

> In any case, thanks for fixing this, which seems to have appeared in
> Git 2.18.  Let's fork a topic from maint, cook it in 'next' and aim
> for eventually merging it down for both 2.19 and 2.18 tracks.

Sounds good,
Dscho

> 
> > +		} else {
> > +			/* we are in a fixup/squash chain */
> >  			const char *p = opts->current_fixups.buf;
> >  			int len = opts->current_fixups.len;
> >  
> > diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
> > index 7d5ea340b3..13f5688135 100755
> > --- a/t/t3415-rebase-autosquash.sh
> > +++ b/t/t3415-rebase-autosquash.sh
> > @@ -330,7 +330,7 @@ test_expect_success 'wrapped original subject' '
> >  	test $base = $parent
> >  '
> >  
> > -test_expect_failure 'abort last squash' '
> > +test_expect_success 'abort last squash' '
> >  	test_when_finished "test_might_fail git rebase --abort" &&
> >  	test_when_finished "git checkout master" &&
>