builtin/rebase: fix leaking `commit.gpgsign` value

In `get_replay_opts()`, we override the `gpg_sign` field that already
got populated by `sequencer_init_config()` in case the user has
"commit.gpgsign" set in their config. This creates a memory leak because
we overwrite the previously assigned value, which may have already
pointed to an allocated string.

Let's plug the memory leak by freeing the value before we overwrite it.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rebase.c

@@ -186,6 +186,7 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	replay.committer_date_is_author_date =
 					opts->committer_date_is_author_date;
 	replay.ignore_date = opts->ignore_date;
+	free(replay.gpg_sign);
 	replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
 	replay.reflog_action = xstrdup(opts->reflog_action);
 	if (opts->strategy)

sequencer.c

@@ -303,6 +303,7 @@ static int git_sequencer_config(const char *k, const char *v,
 	}
 
 	if (!strcmp(k, "commit.gpgsign")) {
+		free(opts->gpg_sign);
 		opts->gpg_sign = git_config_bool(k, v) ? xstrdup("") : NULL;
 		return 0;
 	}

t/t3404-rebase-interactive.sh

@@ -26,6 +26,7 @@ Initial setup:
  touch file "conflict".
 '
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 . "$TEST_DIRECTORY"/lib-rebase.sh

t/t3435-rebase-gpg-sign.sh

@@ -8,6 +8,7 @@ test_description='test rebase --[no-]gpg-sign'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 . "$TEST_DIRECTORY/lib-rebase.sh"
 . "$TEST_DIRECTORY/lib-gpg.sh"

t/t7030-verify-tag.sh

@@ -4,6 +4,7 @@ test_description='signed tag tests'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 . "$TEST_DIRECTORY/lib-gpg.sh"