[PATCH 4/6] rebase -i: fix --committer-date-is-author-date

[Phillip Wood <phillip.wood123@gmail.com>]

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

Johanathan Nieder reported that `rebase --committer-date-is-author-date`
failed with the error "invalid date format: @@2592000 +0000" when the
backend was switched to use the sequencer [1]. This is because when we
read the date from the author script file is already prefixed by '@' so
we do not need to add one. This did not show up in our tests
because once match_object_header_date() fails to match because of the
extra '@' parse_date_basic() strips the prefix and a date with more than
8 digits is parsed as a number of seconds by match_digit().

While fixing this I also noticed that we were not setting
GIT_COMMITTER_DATE in the environment when forking `git merge`. This was
untested. The tests we did have used commits where the author date was
the same as the current value $GIT_COMMITTER_DATE in the environment so
they did not test that we were actually using the author date when
creating the commit.

As we have already read GIT_AUTHOR_DATE into cmd.env_array we now use
that rather than re-reading the author-script file. I've moved the code
that handles opts->ignore date so that all the code setting the child
environment is together and changed it so we no longer set
GIT_COMMITTER_DATE twice when --ignore-date is combined with
--committer-date-is-author-date.

[1] https://lore.kernel.org/git/<20200110231436.GA24315@google.com>

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 sequencer.c                             | 68 ++++++++++---------------
 t/t3433-rebase-options-compatibility.sh | 29 +++++++++--
 2 files changed, 52 insertions(+), 45 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 763ccbbc45..56f6e49289 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -880,17 +880,6 @@ static char *get_author(const char *message)
 	return NULL;
 }
 
-/* Returns a "date" string that needs to be free()'d by the caller */
-static char *read_author_date_or_null(void)
-{
-	char *date;
-
-	if (read_author_script(rebase_path_author_script(),
-			       NULL, NULL, &date, 0))
-		return NULL;
-	return date;
-}
-
 /* Construct a free()able author string with current time as the author date */
 static char *ignore_author_date(const char *author)
 {
@@ -909,16 +898,20 @@ static char *ignore_author_date(const char *author)
 	return strbuf_detach(&new_author, NULL);
 }
 
-static void push_dates(struct child_process *child, int change_committer_date)
+static const char *author_date_from_env_array(const struct argv_array *env)
 {
-	time_t now = time(NULL);
-	struct strbuf date = STRBUF_INIT;
+	int i;
+	const char *date;
 
-	strbuf_addf(&date, "@%"PRIuMAX, (uintmax_t)now);
-	argv_array_pushf(&child->env_array, "GIT_AUTHOR_DATE=%s", date.buf);
-	if (change_committer_date)
-		argv_array_pushf(&child->env_array, "GIT_COMMITTER_DATE=%s", date.buf);
-	strbuf_release(&date);
+	for (i = 0; i < env->argc; i++)
+		if (skip_prefix(env->argv[i],
+				"GIT_AUTHOR_DATE=", &date))
+			return date;
+	/*
+	 * If GIT_AUTHOR_DATE is missing we should have already errored out when
+	 * reading the script
+	 */
+	BUG("GIT_AUTHOR_DATE missing from author script");
 }
 
 static const char staged_changes_advice[] =
@@ -980,31 +973,19 @@ static int run_git_commit(struct repository *r,
 
 	cmd.git_cmd = 1;
 
-	if (opts->committer_date_is_author_date) {
-		int res = -1;
-		struct strbuf datebuf = STRBUF_INIT;
-		char *date = read_author_date_or_null();
-
-		if (!date)
-			return -1;
-
-		strbuf_addf(&datebuf, "@%s", date);
-		res = setenv("GIT_COMMITTER_DATE",
-			     opts->ignore_date ? "" : datebuf.buf, 1);
-
-		strbuf_release(&datebuf);
-		free(date);
-
-		if (res)
-			return -1;
-	}
-
 	if (is_rebase_i(opts) && read_env_script(&cmd.env_array)) {
 		const char *gpg_opt = gpg_sign_opt_quoted(opts);
 
 		return error(_(staged_changes_advice),
 			     gpg_opt, gpg_opt);
 	}
+	if (opts->committer_date_is_author_date)
+		argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+				 opts->ignore_date ?
+				 "" :
+				 author_date_from_env_array(&cmd.env_array));
+	if (opts->ignore_date)
+		argv_array_push(&cmd.env_array, "GIT_AUTHOR_DATE=");
 
 	argv_array_push(&cmd.args, "commit");
 
@@ -1014,8 +995,6 @@ static int run_git_commit(struct repository *r,
 		argv_array_push(&cmd.args, "--amend");
 	if (opts->gpg_sign)
 		argv_array_pushf(&cmd.args, "-S%s", opts->gpg_sign);
-	if (opts->ignore_date)
-		push_dates(&cmd, opts->committer_date_is_author_date);
 	if (defmsg)
 		argv_array_pushl(&cmd.args, "-F", defmsg, NULL);
 	else if (!(flags & EDIT_MSG))
@@ -3615,6 +3594,13 @@ static int do_merge(struct repository *r,
 			ret = error(_(staged_changes_advice), gpg_opt, gpg_opt);
 			goto leave_merge;
 		}
+		if (opts->committer_date_is_author_date)
+			argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+					 opts->ignore_date ?
+					 "" :
+					 author_date_from_env_array(&cmd.env_array));
+		if (opts->ignore_date)
+			argv_array_push(&cmd.env_array, "GIT_AUTHOR_DATE=");
 
 		cmd.git_cmd = 1;
 		argv_array_push(&cmd.args, "merge");
@@ -3635,8 +3621,6 @@ static int do_merge(struct repository *r,
 		argv_array_push(&cmd.args, git_path_merge_msg(r));
 		if (opts->gpg_sign)
 			argv_array_push(&cmd.args, opts->gpg_sign);
-		if (opts->ignore_date)
-			push_dates(&cmd, opts->committer_date_is_author_date);
 
 		/* Add the tips to be merged */
 		for (j = to_merge; j; j = j->next)
diff --git a/t/t3433-rebase-options-compatibility.sh b/t/t3433-rebase-options-compatibility.sh
index 132f577fc9..8247d01442 100755
--- a/t/t3433-rebase-options-compatibility.sh
+++ b/t/t3433-rebase-options-compatibility.sh
@@ -71,15 +71,15 @@ test_expect_success '--ignore-whitespace works with interactive backend' '
 '
 
 test_expect_success '--committer-date-is-author-date works with am backend' '
-	git commit --amend &&
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
 	git rebase --committer-date-is-author-date HEAD^ &&
 	git log -1 --pretty="format:%ai" >authortime &&
 	git log -1 --pretty="format:%ci" >committertime &&
 	test_cmp authortime committertime
 '
 
 test_expect_success '--committer-date-is-author-date works with interactive backend' '
-	git commit --amend &&
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
 	git rebase -i --committer-date-is-author-date HEAD^ &&
 	git log -1 --pretty="format:%ai" >authortime &&
 	git log -1 --pretty="format:%ci" >committertime &&
@@ -88,13 +88,36 @@ test_expect_success '--committer-date-is-author-date works with interactive back
 
 test_expect_success '--committer-date-is-author-date works with rebase -r' '
 	git checkout side &&
-	git merge --no-ff commit3 &&
+	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
 	git rebase -r --root --committer-date-is-author-date &&
 	git log --pretty="format:%ai" >authortime &&
 	git log --pretty="format:%ci" >committertime &&
 	test_cmp authortime committertime
 '
 
+test_expect_success '--committer-date-is-author-date works when forking merge' '
+	git checkout side &&
+	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
+	git rebase -r --root --strategy=resolve --committer-date-is-author-date &&
+	git log --pretty="format:%ai" >authortime &&
+	git log --pretty="format:%ci" >committertime &&
+	test_cmp authortime committertime
+
+'
+
+test_expect_success '--committer-date-is-author-date works when committing conflict resolution' '
+	git checkout commit2 &&
+	GIT_AUTHOR_DATE="@1980 +0000" git commit --amend --only --reset-author &&
+	git log -1 --format=%at HEAD >expect &&
+	test_must_fail git rebase -i --committer-date-is-author-date \
+		--onto HEAD^^ HEAD^ &&
+	echo resolved > foo &&
+	git add foo &&
+	git rebase --continue &&
+	git log -1 --format=%ct HEAD >actual &&
+	test_cmp expect actual
+'
+
 # Checking for +0000 in author time is enough since default
 # timezone is UTC, but the timezone used while committing
 # sets to +0530.
-- 
2.26.0