[GSoC][PATCH v4 3/3] rebase -i: rewrite setup_reflog_action() in C

[Alban Gruin <alban.gruin@gmail.com>]

This rewrites (the misnamed) setup_reflog_action() from shell to C. The
new version is called checkout_onto().

A new command is added to rebase--helper.c, “checkout-base”. The shell
version is then stripped.

As $GIT_REFLOG_ACTION is no longer set at the first call of
checkout_onto(), a call to comment_for_reflog() is added at the
beginning of this function.

If the commit OID provided to checkout_onto() is empty, nothing happens
and no errors are returned, otherwise it would break some
tests (t3404.92 and t3404.93).

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
---
 builtin/rebase--helper.c   |  6 +++++-
 git-rebase--interactive.sh | 15 +--------------
 sequencer.c                | 14 ++++++++++++++
 sequencer.h                |  2 ++
 4 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
index 2dfd55c76..a00b1091d 100644
--- a/builtin/rebase--helper.c
+++ b/builtin/rebase--helper.c
@@ -17,7 +17,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 	enum {
 		CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,
 		CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,
-		ADD_EXEC, APPEND_TODO_HELP, EDIT_TODO, DETACH_ONTO
+		ADD_EXEC, APPEND_TODO_HELP, EDIT_TODO, DETACH_ONTO, CHECKOUT_ONTO
 	} command = 0;
 	struct option options[] = {
 		OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
@@ -53,6 +53,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 			    EDIT_TODO),
 		OPT_CMDMODE(0, "detach-onto", &command,
 			    N_("checkout a commit"), DETACH_ONTO),
+		OPT_CMDMODE(0, "checkout-onto", &command,
+			    N_("checkout the base commit"), CHECKOUT_ONTO),
 		OPT_END()
 	};
 
@@ -98,5 +100,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
 		return !!edit_todo_list(flags);
 	if (command == DETACH_ONTO && argc == 4)
 		return !!detach_onto(&opts, argv[1], argv[2], argv[3], verbose);
+	if (command == CHECKOUT_ONTO && argc == 2)
+		return !!checkout_onto(&opts, argv[1], verbose);
 	usage_with_options(builtin_rebase_helper_usage, options);
 }
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 2f5761d49..375c36fb5 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -112,19 +112,6 @@ initiate_action () {
 	esac
 }
 
-setup_reflog_action () {
-	comment_for_reflog start
-
-	if test ! -z "$switch_to"
-	then
-		GIT_REFLOG_ACTION="$GIT_REFLOG_ACTION: checkout $switch_to"
-		output git checkout "$switch_to" -- ||
-			die "$(eval_gettext "Could not checkout \$switch_to")"
-
-		comment_for_reflog start
-	fi
-}
-
 init_basic_state () {
 	orig_head=$(git rev-parse --verify HEAD) || die "$(gettext "No HEAD?")"
 	mkdir -p "$state_dir" || die "$(eval_gettext "Could not create temporary \$state_dir")"
@@ -206,7 +193,7 @@ git_rebase__interactive () {
 		return 0
 	fi
 
-	setup_reflog_action
+	git rebase--helper --checkout-onto "$switch_to" ${verbose:+--verbose}
 	init_basic_state
 
 	init_revisions_and_shortrevisions
diff --git a/sequencer.c b/sequencer.c
index ee6374921..620b41e96 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -3165,6 +3165,20 @@ int detach_onto(struct replay_opts *opts,
 	return update_ref(NULL, "ORIG_HEAD", &oid, NULL, 0, UPDATE_REFS_MSG_ON_ERR);
 }
 
+int checkout_onto(struct replay_opts *opts, const char *commit,
+		  int verbose)
+{
+	const char *action;
+
+	if (commit && *commit) {
+		action = reflog_message(opts, "start", "checkout %s", commit);
+		if (run_git_checkout(opts, commit, verbose, action))
+			return error(_("Could not checkout %s"), commit);
+	}
+
+	return 0;
+}
+
 static const char rescheduled_advice[] =
 N_("Could not execute the todo command\n"
 "\n"
diff --git a/sequencer.h b/sequencer.h
index 9f0ac5e75..afbb2edf1 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -103,6 +103,8 @@ void commit_post_rewrite(const struct commit *current_head,
 int detach_onto(struct replay_opts *opts,
 		const char *onto_name, const char *onto,
 		const char *orig_head, unsigned verbose);
+int checkout_onto(struct replay_opts *opts, const char *commit,
+		  int verbose);
 
 #define SUMMARY_INITIAL_COMMIT   (1 << 0)
 #define SUMMARY_SHOW_AUTHOR_DATE (1 << 1)
-- 
2.18.0