[PATCH v2] rebase: write script before initializing state

["Øystein Walle" <oystwa@gmail.com>]

If rebase.instructionFormat is invalid the repository is left in a
strange state when the interactive rebase fails. `git status` outputs
both the same as it would have in the normal case *and* something
related to the interactive rebase:

    $ git -c rebase.instructionFormat=blah rebase -i
    fatal: invalid --pretty format: blah
    $ git status
    On branch master
    Your branch is ahead of 'upstream/master' by 1 commit.
      (use "git push" to publish your local commits)

    git-rebase-todo is missing.
    No commands done.
    No commands remaining.
    You are currently editing a commit while rebasing branch 'master' on '8db3019401'.
      (use "git commit --amend" to amend the current commit)
      (use "git rebase --continue" once you are satisfied with your changes)

get_commit_format() calls die() on failure so we cannot handle the error
gracefully. By attempting to write the rebase script before initializing
the state this bad state can be avoided.

Signed-off-by: Øystein Walle <oystwa@gmail.com>
---
So sorry for the delay. I saw that the signoff was missing, then saw
Phillip's review, decided to think about it and then life happened in
the mean time...

This patch is identical to the first one except it has the missing
signoff and a few typos in the commit message corrected. Phillip's
suggestions are noted and appreciated but unfortunately I am unable to
work on the at the moment. And I do think my patch is at least an
improvement albeit perhaps less thorough than it could have been.

Øsse

 builtin/rebase.c             | 42 ++++++++++++++++++------------------
 t/t3415-rebase-autosquash.sh | 10 +++++++++
 2 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 2e8c4ee678..8139816417 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -293,15 +293,6 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
 				&revisions, &shortrevisions))
 		goto cleanup;
 
-	if (init_basic_state(&replay,
-			     opts->head_name ? opts->head_name : "detached HEAD",
-			     opts->onto, &opts->orig_head->object.oid))
-		goto cleanup;
-
-	if (!opts->upstream && opts->squash_onto)
-		write_file(path_squash_onto(), "%s\n",
-			   oid_to_hex(opts->squash_onto));
-
 	strvec_pushl(&make_script_args, "", revisions, NULL);
 	if (opts->restrict_revision)
 		strvec_pushf(&make_script_args, "^%s",
@@ -310,21 +301,30 @@ static int do_interactive_rebase(struct rebase_options *opts, unsigned flags)
 	ret = sequencer_make_script(the_repository, &todo_list.buf,
 				    make_script_args.nr, make_script_args.v,
 				    flags);
-
-	if (ret)
+	if (ret) {
 		error(_("could not generate todo list"));
-	else {
-		discard_index(the_repository->index);
-		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,
-			shortrevisions, opts->onto_name, opts->onto,
-			&opts->orig_head->object.oid, &opts->exec,
-			opts->autosquash, opts->update_refs, &todo_list);
+		goto cleanup;
 	}
 
+	if (init_basic_state(&replay,
+			     opts->head_name ? opts->head_name : "detached HEAD",
+			     opts->onto, &opts->orig_head->object.oid))
+		goto cleanup;
+
+	if (!opts->upstream && opts->squash_onto)
+		write_file(path_squash_onto(), "%s\n",
+			   oid_to_hex(opts->squash_onto));
+
+	discard_index(the_repository->index);
+	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,
+		shortrevisions, opts->onto_name, opts->onto,
+		&opts->orig_head->object.oid, &opts->exec,
+		opts->autosquash, opts->update_refs, &todo_list);
+
 cleanup:
 	replay_opts_release(&replay);
 	free(revisions);
diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
index 26b42a526a..5d093e3a7a 100755
--- a/t/t3415-rebase-autosquash.sh
+++ b/t/t3415-rebase-autosquash.sh
@@ -394,6 +394,16 @@ test_expect_success 'autosquash with empty custom instructionFormat' '
 	)
 '
 
+test_expect_success 'autosquash with invalid custom instructionFormat' '
+	git reset --hard base &&
+	test_commit invalid-instructionFormat-test &&
+	(
+		test_must_fail git -c rebase.instructionFormat=blah \
+			rebase --autosquash  --force-rebase -i HEAD^ &&
+		test_path_is_missing .git/rebase-merge
+	)
+'
+
 set_backup_editor () {
 	write_script backup-editor.sh <<-\EOF
 	cp "$1" .git/backup-"$(basename "$1")"
-- 
2.43.0