rebase -i: fix rewording with --committer-date-is-author-date

baf8ec8d3a (rebase -r: don't write .git/MERGE_MSG when
fast-forwarding, 2021-08-20) stopped reading the author script in
run_git_commit() when rewording a commit. This is normally safe
because "git commit --amend" preserves the authorship. However if the
user passes "--committer-date-is-author-date" then we need to read the
author date from the author script when rewording. Fix this regression
by tightening the check for when it is safe to skip reading the author
script.

Reported-by: Jonas Kittner <jonas.kittner@ruhr-uni-bochum.de>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -983,7 +983,9 @@ static int run_git_commit(const char *defmsg,
 
 	cmd.git_cmd = 1;
 
-	if (is_rebase_i(opts) && !(!defmsg && (flags & AMEND_MSG)) &&
+	if (is_rebase_i(opts) &&
+	    ((opts->committer_date_is_author_date && !opts->ignore_date) ||
+	     !(!defmsg && (flags & AMEND_MSG))) &&
 	    read_env_script(&cmd.env_array)) {
 		const char *gpg_opt = gpg_sign_opt_quoted(opts);
 

t/t3436-rebase-more-options.sh

@@ -82,6 +82,20 @@ test_expect_success '--committer-date-is-author-date works with merge backend' '
 	test_ctime_is_atime -1
 '
 
+test_expect_success '--committer-date-is-author-date works when rewording' '
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_MESSAGE=edited \
+			FAKE_LINES="reword 1" \
+			git rebase -i --committer-date-is-author-date HEAD^
+	) &&
+	test_write_lines edited "" >expect &&
+	git log --format="%B" -1 >actual &&
+	test_cmp expect actual &&
+	test_ctime_is_atime -1
+'
+
 test_expect_success '--committer-date-is-author-date works with rebase -r' '
 	git checkout side &&
 	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
@@ -155,6 +169,21 @@ test_expect_success '--reset-author-date with --committer-date-is-author-date wo
 	test_atime_is_ignored -2
 '
 
+test_expect_success 'reset-author-date with --committer-date-is-author-date works when rewording' '
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_MESSAGE=edited \
+			FAKE_LINES="reword 1" \
+			git rebase -i --committer-date-is-author-date \
+				--reset-author-date HEAD^
+	) &&
+	test_write_lines edited "" >expect &&
+	git log --format="%B" -1 >actual &&
+	test_cmp expect actual &&
+	test_atime_is_ignored -1
+'
+
 test_expect_success '--reset-author-date --committer-date-is-author-date works when forking merge' '
 	GIT_SEQUENCE_EDITOR="echo \"merge -C $(git rev-parse HEAD) commit3\">" \
 		PATH="./test-bin:$PATH" git rebase -i --strategy=test \