1 files changed, 673 insertions, 153 deletions

diff --git a/builtin/gc.c b/builtin/gc.c
index ae34362e93..bcef6a4c8d 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -54,7 +54,6 @@ static const char *prune_worktrees_expire = "3.months.ago";
 static unsigned long big_pack_threshold;
 static unsigned long max_delta_cache_size = DEFAULT_DELTA_CACHE_SIZE;
 
-static struct strvec pack_refs_cmd = STRVEC_INIT;
 static struct strvec reflog = STRVEC_INIT;
 static struct strvec repack = STRVEC_INIT;
 static struct strvec prune = STRVEC_INIT;
@@ -163,6 +162,15 @@ static void gc_config(void)
 	git_config(git_default_config, NULL);
 }
 
+struct maintenance_run_opts;
+static int maintenance_task_pack_refs(MAYBE_UNUSED struct maintenance_run_opts *opts)
+{
+	struct strvec pack_refs_cmd = STRVEC_INIT;
+	strvec_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
+
+	return run_command_v_opt(pack_refs_cmd.v, RUN_GIT_CMD);
+}
+
 static int too_many_loose_objects(void)
 {
 	/*
@@ -494,7 +502,7 @@ static int report_last_gc_error(void)
 		 */
 		warning(_("The last gc run reported the following. "
 			       "Please correct the root cause\n"
-			       "and remove %s.\n"
+			       "and remove %s\n"
 			       "Automatic cleanup will not be performed "
 			       "until the file is removed.\n\n"
 			       "%s"),
@@ -518,8 +526,8 @@ static void gc_before_repack(void)
 	if (done++)
 		return;
 
-	if (pack_refs && run_command_v_opt(pack_refs_cmd.v, RUN_GIT_CMD))
-		die(FAILED_RUN, pack_refs_cmd.v[0]);
+	if (pack_refs && maintenance_task_pack_refs(NULL))
+		die(FAILED_RUN, "pack-refs");
 
 	if (prune_reflogs && run_command_v_opt(reflog.v, RUN_GIT_CMD))
 		die(FAILED_RUN, reflog.v[0]);
@@ -556,7 +564,6 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_gc_usage, builtin_gc_options);
 
-	strvec_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
 	strvec_pushl(&reflog, "reflog", "expire", "--all", NULL);
 	strvec_pushl(&repack, "repack", "-d", "-l", NULL);
 	strvec_pushl(&prune, "prune", "--expire", NULL);
@@ -656,8 +663,8 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	gc_before_repack();
 
 	if (!repository_format_precious_objects) {
-		close_object_store(the_repository->objects);
-		if (run_command_v_opt(repack.v, RUN_GIT_CMD))
+		if (run_command_v_opt(repack.v,
+				      RUN_GIT_CMD | RUN_CLOSE_OBJECT_STORE))
 			die(FAILED_RUN, repack.v[0]);
 
 		if (prune_expire) {
@@ -769,7 +776,7 @@ static int dfs_on_ref(const char *refname,
 	struct commit_list *stack = NULL;
 	struct commit *commit;
 
-	if (!peel_ref(refname, &peeled))
+	if (!peel_iterated_oid(oid, &peeled))
 		oid = &peeled;
 	if (oid_object_info(the_repository, oid, NULL) != OBJ_COMMIT)
 		return 0;
@@ -841,7 +848,7 @@ static int run_write_commit_graph(struct maintenance_run_opts *opts)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
 
-	child.git_cmd = 1;
+	child.git_cmd = child.close_object_store = 1;
 	strvec_pushl(&child.args, "commit-graph", "write",
 		     "--split", "--reachable", NULL);
 
@@ -857,7 +864,6 @@ static int maintenance_task_commit_graph(struct maintenance_run_opts *opts)
 	if (!the_repository->settings.core_commit_graph)
 		return 0;
 
-	close_object_store(the_repository->objects);
 	if (run_write_commit_graph(opts)) {
 		error(_("failed to write commit-graph"));
 		return 1;
@@ -866,56 +872,47 @@ static int maintenance_task_commit_graph(struct maintenance_run_opts *opts)
 	return 0;
 }
 
-static int fetch_remote(const char *remote, struct maintenance_run_opts *opts)
+static int fetch_remote(struct remote *remote, void *cbdata)
 {
+	struct maintenance_run_opts *opts = cbdata;
 	struct child_process child = CHILD_PROCESS_INIT;
 
+	if (remote->skip_default_update)
+		return 0;
+
 	child.git_cmd = 1;
-	strvec_pushl(&child.args, "fetch", remote, "--prune", "--no-tags",
+	strvec_pushl(&child.args, "fetch", remote->name,
+		     "--prefetch", "--prune", "--no-tags",
 		     "--no-write-fetch-head", "--recurse-submodules=no",
-		     "--refmap=", NULL);
+		     NULL);
 
 	if (opts->quiet)
 		strvec_push(&child.args, "--quiet");
 
-	strvec_pushf(&child.args, "+refs/heads/*:refs/prefetch/%s/*", remote);
-
 	return !!run_command(&child);
 }
 
-static int append_remote(struct remote *remote, void *cbdata)
-{
-	struct string_list *remotes = (struct string_list *)cbdata;
-
-	string_list_append(remotes, remote->name);
-	return 0;
-}
-
 static int maintenance_task_prefetch(struct maintenance_run_opts *opts)
 {
-	int result = 0;
-	struct string_list_item *item;
-	struct string_list remotes = STRING_LIST_INIT_DUP;
+	git_config_set_multivar_gently("log.excludedecoration",
+					"refs/prefetch/",
+					"refs/prefetch/",
+					CONFIG_FLAGS_FIXED_VALUE |
+					CONFIG_FLAGS_MULTI_REPLACE);
 
-	if (for_each_remote(append_remote, &remotes)) {
-		error(_("failed to fill remotes"));
-		result = 1;
-		goto cleanup;
+	if (for_each_remote(fetch_remote, opts)) {
+		error(_("failed to prefetch remotes"));
+		return 1;
 	}
 
-	for_each_string_list_item(item, &remotes)
-		result |= fetch_remote(item->string, opts);
-
-cleanup:
-	string_list_clear(&remotes, 0);
-	return result;
+	return 0;
 }
 
 static int maintenance_task_gc(struct maintenance_run_opts *opts)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
 
-	child.git_cmd = 1;
+	child.git_cmd = child.close_object_store = 1;
 	strvec_push(&child.args, "gc");
 
 	if (opts->auto_flag)
@@ -925,7 +922,6 @@ static int maintenance_task_gc(struct maintenance_run_opts *opts)
 	else
 		strvec_push(&child.args, "--no-quiet");
 
-	close_object_store(the_repository->objects);
 	return run_command(&child);
 }
 
@@ -1053,12 +1049,11 @@ static int maintenance_task_loose_objects(struct maintenance_run_opts *opts)
 static int incremental_repack_auto_condition(void)
 {
 	struct packed_git *p;
-	int enabled;
 	int incremental_repack_auto_limit = 10;
 	int count = 0;
 
-	if (git_config_get_bool("core.multiPackIndex", &enabled) ||
-	    !enabled)
+	prepare_repo_settings(the_repository);
+	if (!the_repository->settings.core_multi_pack_index)
 		return 0;
 
 	git_config_get_int("maintenance.incremental-repack.auto",
@@ -1099,14 +1094,12 @@ static int multi_pack_index_expire(struct maintenance_run_opts *opts)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
 
-	child.git_cmd = 1;
+	child.git_cmd = child.close_object_store = 1;
 	strvec_pushl(&child.args, "multi-pack-index", "expire", NULL);
 
 	if (opts->quiet)
 		strvec_push(&child.args, "--no-progress");
 
-	close_object_store(the_repository->objects);
-
 	if (run_command(&child))
 		return error(_("'git multi-pack-index expire' failed"));
 
@@ -1157,7 +1150,7 @@ static int multi_pack_index_repack(struct maintenance_run_opts *opts)
 {
 	struct child_process child = CHILD_PROCESS_INIT;
 
-	child.git_cmd = 1;
+	child.git_cmd = child.close_object_store = 1;
 	strvec_pushl(&child.args, "multi-pack-index", "repack", NULL);
 
 	if (opts->quiet)
@@ -1166,8 +1159,6 @@ static int multi_pack_index_repack(struct maintenance_run_opts *opts)
 	strvec_pushf(&child.args, "--batch-size=%"PRIuMAX,
 				  (uintmax_t)get_auto_pack_size());
 
-	close_object_store(the_repository->objects);
-
 	if (run_command(&child))
 		return error(_("'git multi-pack-index repack' failed"));
 
@@ -1218,6 +1209,7 @@ enum maintenance_task_label {
 	TASK_INCREMENTAL_REPACK,
 	TASK_GC,
 	TASK_COMMIT_GRAPH,
+	TASK_PACK_REFS,
 
 	/* Leave as final value */
 	TASK__COUNT
@@ -1249,6 +1241,11 @@ static struct maintenance_task tasks[] = {
 		maintenance_task_commit_graph,
 		should_write_commit_graph,
 	},
+	[TASK_PACK_REFS] = {
+		"pack-refs",
+		maintenance_task_pack_refs,
+		NULL,
+	},
 };
 
 static int compare_tasks_by_selection(const void *a_, const void *b_)
@@ -1333,6 +1330,8 @@ static void initialize_maintenance_strategy(void)
 		tasks[TASK_INCREMENTAL_REPACK].schedule = SCHEDULE_DAILY;
 		tasks[TASK_LOOSE_OBJECTS].enabled = 1;
 		tasks[TASK_LOOSE_OBJECTS].schedule = SCHEDULE_DAILY;
+		tasks[TASK_PACK_REFS].enabled = 1;
+		tasks[TASK_PACK_REFS].schedule = SCHEDULE_WEEKLY;
 	}
 }
 
@@ -1440,11 +1439,23 @@ static int maintenance_run(int argc, const char **argv, const char *prefix)
 	return maintenance_run_tasks(&opts);
 }
 
+static char *get_maintpath(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char *p = the_repository->worktree ?
+		the_repository->worktree : the_repository->gitdir;
+
+	strbuf_realpath(&sb, p, 1);
+	return strbuf_detach(&sb, NULL);
+}
+
 static int maintenance_register(void)
 {
+	int rc;
 	char *config_value;
 	struct child_process config_set = CHILD_PROCESS_INIT;
 	struct child_process config_get = CHILD_PROCESS_INIT;
+	char *maintpath = get_maintpath();
 
 	/* Disable foreground maintenance */
 	git_config_set("maintenance.auto", "false");
@@ -1457,40 +1468,44 @@ static int maintenance_register(void)
 
 	config_get.git_cmd = 1;
 	strvec_pushl(&config_get.args, "config", "--global", "--get",
-		     "--fixed-value", "maintenance.repo",
-		     the_repository->worktree ? the_repository->worktree
-					      : the_repository->gitdir,
-			 NULL);
+		     "--fixed-value", "maintenance.repo", maintpath, NULL);
 	config_get.out = -1;
 
-	if (start_command(&config_get))
-		return error(_("failed to run 'git config'"));
+	if (start_command(&config_get)) {
+		rc = error(_("failed to run 'git config'"));
+		goto done;
+	}
 
 	/* We already have this value in our config! */
-	if (!finish_command(&config_get))
-		return 0;
+	if (!finish_command(&config_get)) {
+		rc = 0;
+		goto done;
+	}
 
 	config_set.git_cmd = 1;
 	strvec_pushl(&config_set.args, "config", "--add", "--global", "maintenance.repo",
-		     the_repository->worktree ? the_repository->worktree
-					      : the_repository->gitdir,
-		     NULL);
+		     maintpath, NULL);
+
+	rc = run_command(&config_set);
 
-	return run_command(&config_set);
+done:
+	free(maintpath);
+	return rc;
 }
 
 static int maintenance_unregister(void)
 {
+	int rc;
 	struct child_process config_unset = CHILD_PROCESS_INIT;
+	char *maintpath = get_maintpath();
 
 	config_unset.git_cmd = 1;
 	strvec_pushl(&config_unset.args, "config", "--global", "--unset",
-		     "--fixed-value", "maintenance.repo",
-		     the_repository->worktree ? the_repository->worktree
-					      : the_repository->gitdir,
-		     NULL);
+		     "--fixed-value", "maintenance.repo", maintpath, NULL);
 
-	return run_command(&config_unset);
+	rc = run_command(&config_unset);
+	free(maintpath);
+	return rc;
 }
 
 static const char *get_frequency(enum schedule_priority schedule)
@@ -1507,6 +1522,93 @@ static const char *get_frequency(enum schedule_priority schedule)
 	}
 }
 
+/*
+ * get_schedule_cmd` reads the GIT_TEST_MAINT_SCHEDULER environment variable
+ * to mock the schedulers that `git maintenance start` rely on.
+ *
+ * For test purpose, GIT_TEST_MAINT_SCHEDULER can be set to a comma-separated
+ * list of colon-separated key/value pairs where each pair contains a scheduler
+ * and its corresponding mock.
+ *
+ * * If $GIT_TEST_MAINT_SCHEDULER is not set, return false and leave the
+ *   arguments unmodified.
+ *
+ * * If $GIT_TEST_MAINT_SCHEDULER is set, return true.
+ *   In this case, the *cmd value is read as input.
+ *
+ *   * if the input value *cmd is the key of one of the comma-separated list
+ *     item, then *is_available is set to true and *cmd is modified and becomes
+ *     the mock command.
+ *
+ *   * if the input value *cmd isn’t the key of any of the comma-separated list
+ *     item, then *is_available is set to false.
+ *
+ * Ex.:
+ *   GIT_TEST_MAINT_SCHEDULER not set
+ *     +-------+-------------------------------------------------+
+ *     | Input |                     Output                      |
+ *     | *cmd  | return code |       *cmd        | *is_available |
+ *     +-------+-------------+-------------------+---------------+
+ *     | "foo" |    false    | "foo" (unchanged) |  (unchanged)  |
+ *     +-------+-------------+-------------------+---------------+
+ *
+ *   GIT_TEST_MAINT_SCHEDULER set to “foo:./mock_foo.sh,bar:./mock_bar.sh”
+ *     +-------+-------------------------------------------------+
+ *     | Input |                     Output                      |
+ *     | *cmd  | return code |       *cmd        | *is_available |
+ *     +-------+-------------+-------------------+---------------+
+ *     | "foo" |    true     |  "./mock.foo.sh"  |     true      |
+ *     | "qux" |    true     | "qux" (unchanged) |     false     |
+ *     +-------+-------------+-------------------+---------------+
+ */
+static int get_schedule_cmd(const char **cmd, int *is_available)
+{
+	char *testing = xstrdup_or_null(getenv("GIT_TEST_MAINT_SCHEDULER"));
+	struct string_list_item *item;
+	struct string_list list = STRING_LIST_INIT_NODUP;
+
+	if (!testing)
+		return 0;
+
+	if (is_available)
+		*is_available = 0;
+
+	string_list_split_in_place(&list, testing, ',', -1);
+	for_each_string_list_item(item, &list) {
+		struct string_list pair = STRING_LIST_INIT_NODUP;
+
+		if (string_list_split_in_place(&pair, item->string, ':', 2) != 2)
+			continue;
+
+		if (!strcmp(*cmd, pair.items[0].string)) {
+			*cmd = pair.items[1].string;
+			if (is_available)
+				*is_available = 1;
+			string_list_clear(&list, 0);
+			UNLEAK(testing);
+			return 1;
+		}
+	}
+
+	string_list_clear(&list, 0);
+	free(testing);
+	return 1;
+}
+
+static int is_launchctl_available(void)
+{
+	const char *cmd = "launchctl";
+	int is_available;
+	if (get_schedule_cmd(&cmd, &is_available))
+		return is_available;
+
+#ifdef __APPLE__
+	return 1;
+#else
+	return 0;
+#endif
+}
+
 static char *launchctl_service_name(const char *frequency)
 {
 	struct strbuf label = STRBUF_INIT;
@@ -1520,7 +1622,7 @@ static char *launchctl_service_filename(const char *name)
 	struct strbuf filename = STRBUF_INIT;
 	strbuf_addf(&filename, "~/Library/LaunchAgents/%s.plist", name);
 
-	expanded = expand_user_path(filename.buf, 1);
+	expanded = interpolate_path(filename.buf, 1);
 	if (!expanded)
 		die(_("failed to expand path '%s'"), filename.buf);
 
@@ -1533,19 +1635,17 @@ static char *launchctl_get_uid(void)
 	return xstrfmt("gui/%d", getuid());
 }
 
-static int launchctl_boot_plist(int enable, const char *filename, const char *cmd)
+static int launchctl_boot_plist(int enable, const char *filename)
 {
+	const char *cmd = "launchctl";
 	int result;
 	struct child_process child = CHILD_PROCESS_INIT;
 	char *uid = launchctl_get_uid();
 
+	get_schedule_cmd(&cmd, NULL);
 	strvec_split(&child.args, cmd);
-	if (enable)
-		strvec_push(&child.args, "bootstrap");
-	else
-		strvec_push(&child.args, "bootout");
-	strvec_push(&child.args, uid);
-	strvec_push(&child.args, filename);
+	strvec_pushl(&child.args, enable ? "bootstrap" : "bootout", uid,
+		     filename, NULL);
 
 	child.no_stderr = 1;
 	child.no_stdout = 1;
@@ -1559,38 +1659,56 @@ static int launchctl_boot_plist(int enable, const char *filename, const char *cm
 	return result;
 }
 
-static int launchctl_remove_plist(enum schedule_priority schedule, const char *cmd)
+static int launchctl_remove_plist(enum schedule_priority schedule)
 {
 	const char *frequency = get_frequency(schedule);
 	char *name = launchctl_service_name(frequency);
 	char *filename = launchctl_service_filename(name);
-	int result = launchctl_boot_plist(0, filename, cmd);
+	int result = launchctl_boot_plist(0, filename);
 	unlink(filename);
 	free(filename);
 	free(name);
 	return result;
 }
 
-static int launchctl_remove_plists(const char *cmd)
+static int launchctl_remove_plists(void)
 {
-	return launchctl_remove_plist(SCHEDULE_HOURLY, cmd) ||
-		launchctl_remove_plist(SCHEDULE_DAILY, cmd) ||
-		launchctl_remove_plist(SCHEDULE_WEEKLY, cmd);
+	return launchctl_remove_plist(SCHEDULE_HOURLY) ||
+	       launchctl_remove_plist(SCHEDULE_DAILY) ||
+	       launchctl_remove_plist(SCHEDULE_WEEKLY);
 }
 
-static int launchctl_schedule_plist(const char *exec_path, enum schedule_priority schedule, const char *cmd)
+static int launchctl_list_contains_plist(const char *name, const char *cmd)
 {
-	FILE *plist;
-	int i;
+	struct child_process child = CHILD_PROCESS_INIT;
+
+	strvec_split(&child.args, cmd);
+	strvec_pushl(&child.args, "list", name, NULL);
+
+	child.no_stderr = 1;
+	child.no_stdout = 1;
+
+	if (start_command(&child))
+		die(_("failed to start launchctl"));
+
+	/* Returns failure if 'name' doesn't exist. */
+	return !finish_command(&child);
+}
+
+static int launchctl_schedule_plist(const char *exec_path, enum schedule_priority schedule)
+{
+	int i, fd;
 	const char *preamble, *repeat;
 	const char *frequency = get_frequency(schedule);
 	char *name = launchctl_service_name(frequency);
 	char *filename = launchctl_service_filename(name);
+	struct lock_file lk = LOCK_INIT;
+	static unsigned long lock_file_timeout_ms = ULONG_MAX;
+	struct strbuf plist = STRBUF_INIT, plist2 = STRBUF_INIT;
+	struct stat st;
+	const char *cmd = "launchctl";
 
-	if (safe_create_leading_directories(filename))
-		die(_("failed to create directories for '%s'"), filename);
-	plist = xfopen(filename, "w");
-
+	get_schedule_cmd(&cmd, NULL);
 	preamble = "<?xml version=\"1.0\"?>\n"
 		   "<!DOCTYPE plist PUBLIC \"-//Apple//DTD PLIST 1.0//EN\" \"http://www.apple.com/DTDs/PropertyList-1.0.dtd\">\n"
 		   "<plist version=\"1.0\">"
@@ -1608,7 +1726,7 @@ static int launchctl_schedule_plist(const char *exec_path, enum schedule_priorit
 		   "</array>\n"
 		   "<key>StartCalendarInterval</key>\n"
 		   "<array>\n";
-	fprintf(plist, preamble, name, exec_path, exec_path, frequency);
+	strbuf_addf(&plist, preamble, name, exec_path, exec_path, frequency);
 
 	switch (schedule) {
 	case SCHEDULE_HOURLY:
@@ -1617,7 +1735,7 @@ static int launchctl_schedule_plist(const char *exec_path, enum schedule_priorit
 			 "<key>Minute</key><integer>0</integer>\n"
 			 "</dict>\n";
 		for (i = 1; i <= 23; i++)
-			fprintf(plist, repeat, i);
+			strbuf_addf(&plist, repeat, i);
 		break;
 
 	case SCHEDULE_DAILY:
@@ -1627,50 +1745,91 @@ static int launchctl_schedule_plist(const char *exec_path, enum schedule_priorit
 			 "<key>Minute</key><integer>0</integer>\n"
 			 "</dict>\n";
 		for (i = 1; i <= 6; i++)
-			fprintf(plist, repeat, i);
+			strbuf_addf(&plist, repeat, i);
 		break;
 
 	case SCHEDULE_WEEKLY:
-		fprintf(plist,
-			"<dict>\n"
-			"<key>Day</key><integer>0</integer>\n"
-			"<key>Hour</key><integer>0</integer>\n"
-			"<key>Minute</key><integer>0</integer>\n"
-			"</dict>\n");
+		strbuf_addstr(&plist,
+			      "<dict>\n"
+			      "<key>Day</key><integer>0</integer>\n"
+			      "<key>Hour</key><integer>0</integer>\n"
+			      "<key>Minute</key><integer>0</integer>\n"
+			      "</dict>\n");
 		break;
 
 	default:
 		/* unreachable */
 		break;
 	}
-	fprintf(plist, "</array>\n</dict>\n</plist>\n");
-	fclose(plist);
+	strbuf_addstr(&plist, "</array>\n</dict>\n</plist>\n");
+
+	if (safe_create_leading_directories(filename))
+		die(_("failed to create directories for '%s'"), filename);
+
+	if ((long)lock_file_timeout_ms < 0 &&
+	    git_config_get_ulong("gc.launchctlplistlocktimeoutms",
+				 &lock_file_timeout_ms))
+		lock_file_timeout_ms = 150;
 
-	/* bootout might fail if not already running, so ignore */
-	launchctl_boot_plist(0, filename, cmd);
-	if (launchctl_boot_plist(1, filename, cmd))
-		die(_("failed to bootstrap service %s"), filename);
+	fd = hold_lock_file_for_update_timeout(&lk, filename, LOCK_DIE_ON_ERROR,
+					       lock_file_timeout_ms);
+
+	/*
+	 * Does this file already exist? With the intended contents? Is it
+	 * registered already? Then it does not need to be re-registered.
+	 */
+	if (!stat(filename, &st) && st.st_size == plist.len &&
+	    strbuf_read_file(&plist2, filename, plist.len) == plist.len &&
+	    !strbuf_cmp(&plist, &plist2) &&
+	    launchctl_list_contains_plist(name, cmd))
+		rollback_lock_file(&lk);
+	else {
+		if (write_in_full(fd, plist.buf, plist.len) < 0 ||
+		    commit_lock_file(&lk))
+			die_errno(_("could not write '%s'"), filename);
+
+		/* bootout might fail if not already running, so ignore */
+		launchctl_boot_plist(0, filename);
+		if (launchctl_boot_plist(1, filename))
+			die(_("failed to bootstrap service %s"), filename);
+	}
 
 	free(filename);
 	free(name);
+	strbuf_release(&plist);
+	strbuf_release(&plist2);
 	return 0;
 }
 
-static int launchctl_add_plists(const char *cmd)
+static int launchctl_add_plists(void)
 {
 	const char *exec_path = git_exec_path();
 
-	return launchctl_schedule_plist(exec_path, SCHEDULE_HOURLY, cmd) ||
-		launchctl_schedule_plist(exec_path, SCHEDULE_DAILY, cmd) ||
-		launchctl_schedule_plist(exec_path, SCHEDULE_WEEKLY, cmd);
+	return launchctl_schedule_plist(exec_path, SCHEDULE_HOURLY) ||
+	       launchctl_schedule_plist(exec_path, SCHEDULE_DAILY) ||
+	       launchctl_schedule_plist(exec_path, SCHEDULE_WEEKLY);
 }
 
-static int launchctl_update_schedule(int run_maintenance, int fd, const char *cmd)
+static int launchctl_update_schedule(int run_maintenance, int fd)
 {
 	if (run_maintenance)
-		return launchctl_add_plists(cmd);
+		return launchctl_add_plists();
 	else
-		return launchctl_remove_plists(cmd);
+		return launchctl_remove_plists();
+}
+
+static int is_schtasks_available(void)
+{
+	const char *cmd = "schtasks";
+	int is_available;
+	if (get_schedule_cmd(&cmd, &is_available))
+		return is_available;
+
+#ifdef GIT_WINDOWS_NATIVE
+	return 1;
+#else
+	return 0;
+#endif
 }
 
 static char *schtasks_task_name(const char *frequency)
@@ -1680,13 +1839,15 @@ static char *schtasks_task_name(const char *frequency)
 	return strbuf_detach(&label, NULL);
 }
 
-static int schtasks_remove_task(enum schedule_priority schedule, const char *cmd)
+static int schtasks_remove_task(enum schedule_priority schedule)
 {
+	const char *cmd = "schtasks";
 	int result;
 	struct strvec args = STRVEC_INIT;
 	const char *frequency = get_frequency(schedule);
 	char *name = schtasks_task_name(frequency);
 
+	get_schedule_cmd(&cmd, NULL);
 	strvec_split(&args, cmd);
 	strvec_pushl(&args, "/delete", "/tn", name, "/f", NULL);
 
@@ -1697,15 +1858,16 @@ static int schtasks_remove_task(enum schedule_priority schedule, const char *cmd
 	return result;
 }
 
-static int schtasks_remove_tasks(const char *cmd)
+static int schtasks_remove_tasks(void)
 {
-	return schtasks_remove_task(SCHEDULE_HOURLY, cmd) ||
-		schtasks_remove_task(SCHEDULE_DAILY, cmd) ||
-		schtasks_remove_task(SCHEDULE_WEEKLY, cmd);
+	return schtasks_remove_task(SCHEDULE_HOURLY) ||
+	       schtasks_remove_task(SCHEDULE_DAILY) ||
+	       schtasks_remove_task(SCHEDULE_WEEKLY);
 }
 
-static int schtasks_schedule_task(const char *exec_path, enum schedule_priority schedule, const char *cmd)
+static int schtasks_schedule_task(const char *exec_path, enum schedule_priority schedule)
 {
+	const char *cmd = "schtasks";
 	int result;
 	struct child_process child = CHILD_PROCESS_INIT;
 	const char *xml;
@@ -1714,6 +1876,8 @@ static int schtasks_schedule_task(const char *exec_path, enum schedule_priority
 	char *name = schtasks_task_name(frequency);
 	struct strbuf tfilename = STRBUF_INIT;
 
+	get_schedule_cmd(&cmd, NULL);
+
 	strbuf_addf(&tfilename, "%s/schedule_%s_XXXXXX",
 		    get_git_common_dir(), frequency);
 	tfile = xmks_tempfile(tfilename.buf);
@@ -1818,28 +1982,67 @@ static int schtasks_schedule_task(const char *exec_path, enum schedule_priority
 	return result;
 }
 
-static int schtasks_schedule_tasks(const char *cmd)
+static int schtasks_schedule_tasks(void)
 {
 	const char *exec_path = git_exec_path();
 
-	return schtasks_schedule_task(exec_path, SCHEDULE_HOURLY, cmd) ||
-		schtasks_schedule_task(exec_path, SCHEDULE_DAILY, cmd) ||
-		schtasks_schedule_task(exec_path, SCHEDULE_WEEKLY, cmd);
+	return schtasks_schedule_task(exec_path, SCHEDULE_HOURLY) ||
+	       schtasks_schedule_task(exec_path, SCHEDULE_DAILY) ||
+	       schtasks_schedule_task(exec_path, SCHEDULE_WEEKLY);
 }
 
-static int schtasks_update_schedule(int run_maintenance, int fd, const char *cmd)
+static int schtasks_update_schedule(int run_maintenance, int fd)
 {
 	if (run_maintenance)
-		return schtasks_schedule_tasks(cmd);
+		return schtasks_schedule_tasks();
 	else
-		return schtasks_remove_tasks(cmd);
+		return schtasks_remove_tasks();
+}
+
+MAYBE_UNUSED
+static int check_crontab_process(const char *cmd)
+{
+	struct child_process child = CHILD_PROCESS_INIT;
+
+	strvec_split(&child.args, cmd);
+	strvec_push(&child.args, "-l");
+	child.no_stdin = 1;
+	child.no_stdout = 1;
+	child.no_stderr = 1;
+	child.silent_exec_failure = 1;
+
+	if (start_command(&child))
+		return 0;
+	/* Ignore exit code, as an empty crontab will return error. */
+	finish_command(&child);
+	return 1;
+}
+
+static int is_crontab_available(void)
+{
+	const char *cmd = "crontab";
+	int is_available;
+
+	if (get_schedule_cmd(&cmd, &is_available))
+		return is_available;
+
+#ifdef __APPLE__
+	/*
+	 * macOS has cron, but it requires special permissions and will
+	 * create a UI alert when attempting to run this command.
+	 */
+	return 0;
+#else
+	return check_crontab_process(cmd);
+#endif
 }
 
 #define BEGIN_LINE "# BEGIN GIT MAINTENANCE SCHEDULE"
 #define END_LINE "# END GIT MAINTENANCE SCHEDULE"
 
-static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
+static int crontab_update_schedule(int run_maintenance, int fd)
 {
+	const char *cmd = "crontab";
 	int result = 0;
 	int in_old_region = 0;
 	struct child_process crontab_list = CHILD_PROCESS_INIT;
@@ -1847,6 +2050,7 @@ static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
 	FILE *cron_list, *cron_in;
 	struct strbuf line = STRBUF_INIT;
 
+	get_schedule_cmd(&cmd, NULL);
 	strvec_split(&crontab_list.args, cmd);
 	strvec_push(&crontab_list.args, "-l");
 	crontab_list.in = -1;
@@ -1887,6 +2091,7 @@ static int crontab_update_schedule(int run_maintenance, int fd, const char *cmd)
 		else if (!in_old_region)
 			fprintf(cron_in, "%s\n", line.buf);
 	}
+	strbuf_release(&line);
 
 	if (run_maintenance) {
 		struct strbuf line_format = STRBUF_INIT;
@@ -1922,61 +2127,376 @@ done_editing:
 	return result;
 }
 
+static int real_is_systemd_timer_available(void)
+{
+	struct child_process child = CHILD_PROCESS_INIT;
+
+	strvec_pushl(&child.args, "systemctl", "--user", "list-timers", NULL);
+	child.no_stdin = 1;
+	child.no_stdout = 1;
+	child.no_stderr = 1;
+	child.silent_exec_failure = 1;
+
+	if (start_command(&child))
+		return 0;
+	if (finish_command(&child))
+		return 0;
+	return 1;
+}
+
+static int is_systemd_timer_available(void)
+{
+	const char *cmd = "systemctl";
+	int is_available;
+
+	if (get_schedule_cmd(&cmd, &is_available))
+		return is_available;
+
+	return real_is_systemd_timer_available();
+}
+
+static char *xdg_config_home_systemd(const char *filename)
+{
+	return xdg_config_home_for("systemd/user", filename);
+}
+
+static int systemd_timer_enable_unit(int enable,
+				     enum schedule_priority schedule)
+{
+	const char *cmd = "systemctl";
+	struct child_process child = CHILD_PROCESS_INIT;
+	const char *frequency = get_frequency(schedule);
+
+	/*
+	 * Disabling the systemd unit while it is already disabled makes
+	 * systemctl print an error.
+	 * Let's ignore it since it means we already are in the expected state:
+	 * the unit is disabled.
+	 *
+	 * On the other hand, enabling a systemd unit which is already enabled
+	 * produces no error.
+	 */
+	if (!enable)
+		child.no_stderr = 1;
+
+	get_schedule_cmd(&cmd, NULL);
+	strvec_split(&child.args, cmd);
+	strvec_pushl(&child.args, "--user", enable ? "enable" : "disable",
+		     "--now", NULL);
+	strvec_pushf(&child.args, "git-maintenance@%s.timer", frequency);
+
+	if (start_command(&child))
+		return error(_("failed to start systemctl"));
+	if (finish_command(&child))
+		/*
+		 * Disabling an already disabled systemd unit makes
+		 * systemctl fail.
+		 * Let's ignore this failure.
+		 *
+		 * Enabling an enabled systemd unit doesn't fail.
+		 */
+		if (enable)
+			return error(_("failed to run systemctl"));
+	return 0;
+}
+
+static int systemd_timer_delete_unit_templates(void)
+{
+	int ret = 0;
+	char *filename = xdg_config_home_systemd("git-maintenance@.timer");
+	if (unlink(filename) && !is_missing_file_error(errno))
+		ret = error_errno(_("failed to delete '%s'"), filename);
+	FREE_AND_NULL(filename);
+
+	filename = xdg_config_home_systemd("git-maintenance@.service");
+	if (unlink(filename) && !is_missing_file_error(errno))
+		ret = error_errno(_("failed to delete '%s'"), filename);
+
+	free(filename);
+	return ret;
+}
+
+static int systemd_timer_delete_units(void)
+{
+	return systemd_timer_enable_unit(0, SCHEDULE_HOURLY) ||
+	       systemd_timer_enable_unit(0, SCHEDULE_DAILY) ||
+	       systemd_timer_enable_unit(0, SCHEDULE_WEEKLY) ||
+	       systemd_timer_delete_unit_templates();
+}
+
+static int systemd_timer_write_unit_templates(const char *exec_path)
+{
+	char *filename;
+	FILE *file;
+	const char *unit;
+
+	filename = xdg_config_home_systemd("git-maintenance@.timer");
+	if (safe_create_leading_directories(filename)) {
+		error(_("failed to create directories for '%s'"), filename);
+		goto error;
+	}
+	file = fopen_or_warn(filename, "w");
+	if (file == NULL)
+		goto error;
+
+	unit = "# This file was created and is maintained by Git.\n"
+	       "# Any edits made in this file might be replaced in the future\n"
+	       "# by a Git command.\n"
+	       "\n"
+	       "[Unit]\n"
+	       "Description=Optimize Git repositories data\n"
+	       "\n"
+	       "[Timer]\n"
+	       "OnCalendar=%i\n"
+	       "Persistent=true\n"
+	       "\n"
+	       "[Install]\n"
+	       "WantedBy=timers.target\n";
+	if (fputs(unit, file) == EOF) {
+		error(_("failed to write to '%s'"), filename);
+		fclose(file);
+		goto error;
+	}
+	if (fclose(file) == EOF) {
+		error_errno(_("failed to flush '%s'"), filename);
+		goto error;
+	}
+	free(filename);
+
+	filename = xdg_config_home_systemd("git-maintenance@.service");
+	file = fopen_or_warn(filename, "w");
+	if (file == NULL)
+		goto error;
+
+	unit = "# This file was created and is maintained by Git.\n"
+	       "# Any edits made in this file might be replaced in the future\n"
+	       "# by a Git command.\n"
+	       "\n"
+	       "[Unit]\n"
+	       "Description=Optimize Git repositories data\n"
+	       "\n"
+	       "[Service]\n"
+	       "Type=oneshot\n"
+	       "ExecStart=\"%s/git\" --exec-path=\"%s\" for-each-repo --config=maintenance.repo maintenance run --schedule=%%i\n"
+	       "LockPersonality=yes\n"
+	       "MemoryDenyWriteExecute=yes\n"
+	       "NoNewPrivileges=yes\n"
+	       "RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6\n"
+	       "RestrictNamespaces=yes\n"
+	       "RestrictRealtime=yes\n"
+	       "RestrictSUIDSGID=yes\n"
+	       "SystemCallArchitectures=native\n"
+	       "SystemCallFilter=@system-service\n";
+	if (fprintf(file, unit, exec_path, exec_path) < 0) {
+		error(_("failed to write to '%s'"), filename);
+		fclose(file);
+		goto error;
+	}
+	if (fclose(file) == EOF) {
+		error_errno(_("failed to flush '%s'"), filename);
+		goto error;
+	}
+	free(filename);
+	return 0;
+
+error:
+	free(filename);
+	systemd_timer_delete_unit_templates();
+	return -1;
+}
+
+static int systemd_timer_setup_units(void)
+{
+	const char *exec_path = git_exec_path();
+
+	int ret = systemd_timer_write_unit_templates(exec_path) ||
+		  systemd_timer_enable_unit(1, SCHEDULE_HOURLY) ||
+		  systemd_timer_enable_unit(1, SCHEDULE_DAILY) ||
+		  systemd_timer_enable_unit(1, SCHEDULE_WEEKLY);
+	if (ret)
+		systemd_timer_delete_units();
+	return ret;
+}
+
+static int systemd_timer_update_schedule(int run_maintenance, int fd)
+{
+	if (run_maintenance)
+		return systemd_timer_setup_units();
+	else
+		return systemd_timer_delete_units();
+}
+
+enum scheduler {
+	SCHEDULER_INVALID = -1,
+	SCHEDULER_AUTO,
+	SCHEDULER_CRON,
+	SCHEDULER_SYSTEMD,
+	SCHEDULER_LAUNCHCTL,
+	SCHEDULER_SCHTASKS,
+};
+
+static const struct {
+	const char *name;
+	int (*is_available)(void);
+	int (*update_schedule)(int run_maintenance, int fd);
+} scheduler_fn[] = {
+	[SCHEDULER_CRON] = {
+		.name = "crontab",
+		.is_available = is_crontab_available,
+		.update_schedule = crontab_update_schedule,
+	},
+	[SCHEDULER_SYSTEMD] = {
+		.name = "systemctl",
+		.is_available = is_systemd_timer_available,
+		.update_schedule = systemd_timer_update_schedule,
+	},
+	[SCHEDULER_LAUNCHCTL] = {
+		.name = "launchctl",
+		.is_available = is_launchctl_available,
+		.update_schedule = launchctl_update_schedule,
+	},
+	[SCHEDULER_SCHTASKS] = {
+		.name = "schtasks",
+		.is_available = is_schtasks_available,
+		.update_schedule = schtasks_update_schedule,
+	},
+};
+
+static enum scheduler parse_scheduler(const char *value)
+{
+	if (!value)
+		return SCHEDULER_INVALID;
+	else if (!strcasecmp(value, "auto"))
+		return SCHEDULER_AUTO;
+	else if (!strcasecmp(value, "cron") || !strcasecmp(value, "crontab"))
+		return SCHEDULER_CRON;
+	else if (!strcasecmp(value, "systemd") ||
+		 !strcasecmp(value, "systemd-timer"))
+		return SCHEDULER_SYSTEMD;
+	else if (!strcasecmp(value, "launchctl"))
+		return SCHEDULER_LAUNCHCTL;
+	else if (!strcasecmp(value, "schtasks"))
+		return SCHEDULER_SCHTASKS;
+	else
+		return SCHEDULER_INVALID;
+}
+
+static int maintenance_opt_scheduler(const struct option *opt, const char *arg,
+				     int unset)
+{
+	enum scheduler *scheduler = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
+	*scheduler = parse_scheduler(arg);
+	if (*scheduler == SCHEDULER_INVALID)
+		return error(_("unrecognized --scheduler argument '%s'"), arg);
+	return 0;
+}
+
+struct maintenance_start_opts {
+	enum scheduler scheduler;
+};
+
+static enum scheduler resolve_scheduler(enum scheduler scheduler)
+{
+	if (scheduler != SCHEDULER_AUTO)
+		return scheduler;
+
 #if defined(__APPLE__)
-static const char platform_scheduler[] = "launchctl";
+	return SCHEDULER_LAUNCHCTL;
+
 #elif defined(GIT_WINDOWS_NATIVE)
-static const char platform_scheduler[] = "schtasks";
+	return SCHEDULER_SCHTASKS;
+
+#elif defined(__linux__)
+	if (is_systemd_timer_available())
+		return SCHEDULER_SYSTEMD;
+	else if (is_crontab_available())
+		return SCHEDULER_CRON;
+	else
+		die(_("neither systemd timers nor crontab are available"));
+
 #else
-static const char platform_scheduler[] = "crontab";
+	return SCHEDULER_CRON;
 #endif
+}
 
-static int update_background_schedule(int enable)
+static void validate_scheduler(enum scheduler scheduler)
 {
-	int result;
-	const char *scheduler = platform_scheduler;
-	const char *cmd = scheduler;
-	char *testing;
+	if (scheduler == SCHEDULER_INVALID)
+		BUG("invalid scheduler");
+	if (scheduler == SCHEDULER_AUTO)
+		BUG("resolve_scheduler should have been called before");
+
+	if (!scheduler_fn[scheduler].is_available())
+		die(_("%s scheduler is not available"),
+		    scheduler_fn[scheduler].name);
+}
+
+static int update_background_schedule(const struct maintenance_start_opts *opts,
+				      int enable)
+{
+	unsigned int i;
+	int result = 0;
 	struct lock_file lk;
 	char *lock_path = xstrfmt("%s/schedule", the_repository->objects->odb->path);
 
-	testing = xstrdup_or_null(getenv("GIT_TEST_MAINT_SCHEDULER"));
-	if (testing) {
-		char *sep = strchr(testing, ':');
-		if (!sep)
-			die("GIT_TEST_MAINT_SCHEDULER unparseable: %s", testing);
-		*sep = '\0';
-		scheduler = testing;
-		cmd = sep + 1;
+	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0) {
+		free(lock_path);
+		return error(_("another process is scheduling background maintenance"));
 	}
 
-	if (hold_lock_file_for_update(&lk, lock_path, LOCK_NO_DEREF) < 0)
-		return error(_("another process is scheduling background maintenance"));
+	for (i = 1; i < ARRAY_SIZE(scheduler_fn); i++) {
+		if (enable && opts->scheduler == i)
+			continue;
+		if (!scheduler_fn[i].is_available())
+			continue;
+		scheduler_fn[i].update_schedule(0, get_lock_file_fd(&lk));
+	}
 
-	if (!strcmp(scheduler, "launchctl"))
-		result = launchctl_update_schedule(enable, get_lock_file_fd(&lk), cmd);
-	else if (!strcmp(scheduler, "schtasks"))
-		result = schtasks_update_schedule(enable, get_lock_file_fd(&lk), cmd);
-	else if (!strcmp(scheduler, "crontab"))
-		result = crontab_update_schedule(enable, get_lock_file_fd(&lk), cmd);
-	else
-		die("unknown background scheduler: %s", scheduler);
+	if (enable)
+		result = scheduler_fn[opts->scheduler].update_schedule(
+			1, get_lock_file_fd(&lk));
 
 	rollback_lock_file(&lk);
-	free(testing);
+
+	free(lock_path);
 	return result;
 }
 
-static int maintenance_start(void)
+static const char *const builtin_maintenance_start_usage[] = {
+	N_("git maintenance start [--scheduler=<scheduler>]"),
+	NULL
+};
+
+static int maintenance_start(int argc, const char **argv, const char *prefix)
 {
+	struct maintenance_start_opts opts = { 0 };
+	struct option options[] = {
+		OPT_CALLBACK_F(
+			0, "scheduler", &opts.scheduler, N_("scheduler"),
+			N_("scheduler to trigger git maintenance run"),
+			PARSE_OPT_NONEG, maintenance_opt_scheduler),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options,
+			     builtin_maintenance_start_usage, 0);
+	if (argc)
+		usage_with_options(builtin_maintenance_start_usage, options);
+
+	opts.scheduler = resolve_scheduler(opts.scheduler);
+	validate_scheduler(opts.scheduler);
+
 	if (maintenance_register())
 		warning(_("failed to add repo to global config"));
-
-	return update_background_schedule(1);
+	return update_background_schedule(&opts, 1);
 }
 
 static int maintenance_stop(void)
 {
-	return update_background_schedule(0);
+	return update_background_schedule(NULL, 0);
 }
 
 static const char builtin_maintenance_usage[] =	N_("git maintenance <subcommand> [<options>]");
@@ -1990,7 +2510,7 @@ int cmd_maintenance(int argc, const char **argv, const char *prefix)
 	if (!strcmp(argv[1], "run"))
 		return maintenance_run(argc - 1, argv + 1, prefix);
 	if (!strcmp(argv[1], "start"))
-		return maintenance_start();
+		return maintenance_start(argc - 1, argv + 1, prefix);
 	if (!strcmp(argv[1], "stop"))
 		return maintenance_stop();
 	if (!strcmp(argv[1], "register"))