[PATCH v3 6/7] maintenance: use default schedule if not configured

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

The 'git maintenance (register|start)' subcommands add the current
repository to the global Git config so maintenance will operate on that
repository. It does not specify what maintenance should occur or how
often.

If a user sets any 'maintenance.<task>.schedule' config value, then
they have chosen a specific schedule for themselves and Git should
respect that when running 'git maintenance run --schedule=<frequency>'.

To make this process extremely simple for users, assume a default
schedule when no 'maintenance.<task>.schedule' or '...enabled' config
settings are concretely set. This is only an in-process assumption, so
future versions of Git could adjust this expected schedule.

Helped-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-maintenance.txt | 15 ++++++++
 builtin/gc.c                      | 58 +++++++++++++++++++++++++++++++
 t/t7900-maintenance.sh            | 11 +++---
 3 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/Documentation/git-maintenance.txt b/Documentation/git-maintenance.txt
index 7628a6d157..52fff86844 100644
--- a/Documentation/git-maintenance.txt
+++ b/Documentation/git-maintenance.txt
@@ -37,6 +37,21 @@ register::
 	`maintenance.<task>.schedule`. The tasks that are enabled are safe
 	for running in the background without disrupting foreground
 	processes.
++
+If your repository has no `maintenance.<task>.schedule` configuration
+values set, then Git will use a recommended default schedule that performs
+background maintenance that will not interrupt foreground commands. The
+default schedule is as follows:
++
+* `gc`: disabled.
+* `commit-graph`: hourly.
+* `prefetch`: hourly.
+* `loose-objects`: daily.
+* `incremental-repack`: daily.
++
+`git maintenance register` will also disable foreground maintenance by
+setting `maintenance.auto = false` in the current repository. This config
+setting will remain after a `git maintenance unregister` command.
 
 run::
 	Run one or more maintenance tasks. If one or more `--task` options
diff --git a/builtin/gc.c b/builtin/gc.c
index a387f46585..965690704b 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1251,6 +1251,59 @@ static int compare_tasks_by_selection(const void *a_, const void *b_)
 	return b->selected_order - a->selected_order;
 }
 
+static int has_schedule_config(void)
+{
+	int i, found = 0;
+	struct strbuf config_name = STRBUF_INIT;
+	size_t prefix;
+
+	strbuf_addstr(&config_name, "maintenance.");
+	prefix = config_name.len;
+
+	for (i = 0; !found && i < TASK__COUNT; i++) {
+		char *value;
+
+		strbuf_setlen(&config_name, prefix);
+		strbuf_addf(&config_name, "%s.schedule", tasks[i].name);
+
+		if (!git_config_get_string(config_name.buf, &value)) {
+			found = 1;
+			FREE_AND_NULL(value);
+		}
+
+		strbuf_setlen(&config_name, prefix);
+		strbuf_addf(&config_name, "%s.enabled", tasks[i].name);
+
+		if (!git_config_get_string(config_name.buf, &value)) {
+			found = 1;
+			FREE_AND_NULL(value);
+		}
+	}
+
+	strbuf_release(&config_name);
+	return found;
+}
+
+static void set_recommended_schedule(void)
+{
+	if (has_schedule_config())
+		return;
+
+	tasks[TASK_GC].enabled = 0;
+
+	tasks[TASK_PREFETCH].enabled = 1;
+	tasks[TASK_PREFETCH].schedule = SCHEDULE_HOURLY;
+
+	tasks[TASK_COMMIT_GRAPH].enabled = 1;
+	tasks[TASK_COMMIT_GRAPH].schedule = SCHEDULE_HOURLY;
+
+	tasks[TASK_LOOSE_OBJECTS].enabled = 1;
+	tasks[TASK_LOOSE_OBJECTS].schedule = SCHEDULE_DAILY;
+
+	tasks[TASK_INCREMENTAL_REPACK].enabled = 1;
+	tasks[TASK_INCREMENTAL_REPACK].schedule = SCHEDULE_DAILY;
+}
+
 static int maintenance_run_tasks(struct maintenance_run_opts *opts)
 {
 	int i, found_selected = 0;
@@ -1280,6 +1333,8 @@ static int maintenance_run_tasks(struct maintenance_run_opts *opts)
 
 	if (found_selected)
 		QSORT(tasks, TASK__COUNT, compare_tasks_by_selection);
+	else if (opts->schedule != SCHEDULE_NONE)
+		set_recommended_schedule();
 
 	for (i = 0; i < TASK__COUNT; i++) {
 		if (found_selected && tasks[i].selected_order < 0)
@@ -1417,6 +1472,9 @@ static int maintenance_register(void)
 	if (!the_repository || !the_repository->gitdir)
 		return 0;
 
+	/* Disable foreground maintenance */
+	git_config_set("maintenance.auto", "false");
+
 	config_get.git_cmd = 1;
 	strvec_pushl(&config_get.args, "config", "--global", "--get", "maintenance.repo",
 		     the_repository->worktree ? the_repository->worktree
diff --git a/t/t7900-maintenance.sh b/t/t7900-maintenance.sh
index 7715e40391..7154987fd2 100755
--- a/t/t7900-maintenance.sh
+++ b/t/t7900-maintenance.sh
@@ -305,11 +305,14 @@ test_expect_success 'register and unregister' '
 	git config --global --add maintenance.repo /existing1 &&
 	git config --global --add maintenance.repo /existing2 &&
 	git config --global --get-all maintenance.repo >before &&
+
 	git maintenance register &&
-	git config --global --get-all maintenance.repo >actual &&
-	cp before after &&
-	pwd >>after &&
-	test_cmp after actual &&
+	test_cmp_config false maintenance.auto &&
+	git config --global --get-all maintenance.repo >between &&
+	cp before expect &&
+	pwd >>expect &&
+	test_cmp expect between &&
+
 	git maintenance unregister &&
 	git config --global --get-all maintenance.repo >actual &&
 	test_cmp before actual
-- 
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