[PATCH 1/1] maintenance: fix a SEGFAULT when no repository

[Rafael Silva <rafaeloliveira.cs@gmail.com>]

The "git maintenance run" and "git maintenance start" commands holds a
file-based lock at the .git/maintenance.lock and .git/schedule.lock
respectively. These locks are used to ensure only one maintenance process
is executed at the time as both operations involves writing data into
the git repository.

The path to the lock file is built using the "the_repository->objects->odb->path"
that results in SEGFAULT when we have no repository available as
"the_repository->objects->odb" is set to NULL.

Let's teach the maintenance_run_tasks() and update_background_schedule() to return
an error and fails the command when we have no repository available.

Signed-off-by: Rafael Silva <rafaeloliveira.cs@gmail.com>

---
 builtin/gc.c           | 14 ++++++++++++--
 t/t7900-maintenance.sh |  5 +++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 3d258b60c2..d133d93a86 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1265,9 +1265,14 @@ static int maintenance_run_tasks(struct maintenance_run_opts *opts)
 {
 	int i, found_selected = 0;
 	int result = 0;
+	char *lock_path;
 	struct lock_file lk;
 	struct repository *r = the_repository;
-	char *lock_path = xstrfmt("%s/maintenance", r->objects->odb->path);
+
+	if (!r || !r->gitdir)
+		return error(_("not a git repository"));
+
+	lock_path = xstrfmt("%s/maintenance", the_repository->objects->odb->path);
 
 	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0) {
 		/*
@@ -1513,8 +1518,13 @@ static int update_background_schedule(int run_maintenance)
 	FILE *cron_list, *cron_in;
 	const char *crontab_name;
 	struct strbuf line = STRBUF_INIT;
+	char *lock_path;
 	struct lock_file lk;
-	char *lock_path = xstrfmt("%s/schedule", the_repository->objects->odb->path);
+
+	if (!the_repository || !the_repository->gitdir)
+		return error(_("not a git repository"));
+
+	lock_path = xstrfmt("%s/schedule", the_repository->objects->odb->path);
 
 	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0)
 		return error(_("another process is scheduling background maintenance"));
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index d9e68bb2bf..bb3556888d 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -441,4 +441,9 @@ test_expect_success 'register preserves existing strategy' '
 	test_config maintenance.strategy incremental
 '
 
+test_expect_success 'run and start command fails when no git repository' '
+	test_must_fail git -C /tmp/ maintenance run &&
+	test_must_fail git -C /tmp/ maintenance start
+'
+
 test_done
-- 
2.29.2.505.g04529851e5