maintenance: create maintenance.<task>.enabled config

Currently, a normal run of "git maintenance run" will only run the 'gc'
task, as it is the only one enabled. This is mostly for backwards-
compatible reasons since "git maintenance run --auto" commands replaced
previous "git gc --auto" commands after some Git processes. Users could
manually run specific maintenance tasks by calling "git maintenance run
--task=<task>" directly.

Allow users to customize which steps are run automatically using config.
The 'maintenance.<task>.enabled' option then can turn on these other
tasks (or turn off the 'gc' task).

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -398,6 +398,8 @@ include::config/mailinfo.txt[]
 
 include::config/mailmap.txt[]
 
+include::config/maintenance.txt[]
+
 include::config/man.txt[]
 
 include::config/merge.txt[]

Documentation/config/maintenance.txt

@@ -0,0 +1,6 @@
+maintenance.<task>.enabled::
+	This boolean config option controls whether the maintenance task
+	with name `<task>` is run when no `--task` option is specified to
+	`git maintenance run`. These config values are ignored if a
+	`--task` option exists. By default, only `maintenance.gc.enabled`
+	is true.

Documentation/git-maintenance.txt

@@ -30,9 +30,11 @@ SUBCOMMANDS
 -----------
 
 run::
-	Run one or more maintenance tasks. If one or more `--task=<task>`
+	Run one or more maintenance tasks. If one or more `--task` options
-	options are specified, then those tasks are run in the provided
+	are specified, then those tasks are run in that order. Otherwise,
-	order. Otherwise, only the `gc` task is run.
+	the tasks are determined by which `maintenance.<task>.enabled`
+	config options are true. By default, only `maintenance.gc.enabled`
+	is true.
 
 TASKS
 -----
@@ -67,8 +69,10 @@ OPTIONS
 
 --task=<task>::
 	If this option is specified one or more times, then only run the
-	specified tasks in the specified order. See the 'TASKS' section
+	specified tasks in the specified order. If no `--task=<task>`
-	for the list of accepted `<task>` values.
+	arguments are specified, then only the tasks with
+	`maintenance.<task>.enabled` configured as `true` are considered.
+	See the 'TASKS' section for the list of accepted `<task>` values.
 
 GIT
 ---

builtin/gc.c

@@ -841,6 +841,24 @@ static int maintenance_run_tasks(struct maintenance_run_opts *opts)
 	return result;
 }
 
+static void initialize_task_config(void)
+{
+	int i;
+	struct strbuf config_name = STRBUF_INIT;
+	for (i = 0; i < TASK__COUNT; i++) {
+		int config_value;
+
+		strbuf_setlen(&config_name, 0);
+		strbuf_addf(&config_name, "maintenance.%s.enabled",
+			    tasks[i].name);
+
+		if (!git_config_get_bool(config_name.buf, &config_value))
+			tasks[i].enabled = config_value;
+	}
+
+	strbuf_release(&config_name);
+}
+
 static int task_option_parse(const struct option *opt,
 			     const char *arg, int unset)
 {
@@ -889,6 +907,7 @@ static int maintenance_run(int argc, const char **argv, const char *prefix)
 	memset(&opts, 0, sizeof(opts));
 
 	opts.quiet = !isatty(2);
+	initialize_task_config();
 
 	for (i = 0; i < TASK__COUNT; i++)
 		tasks[i].selected_order = -1;

t/t7900-maintenance.sh

@@ -27,6 +27,14 @@ test_expect_success 'run [--auto|--quiet]' '
 	test_subcommand git gc --no-quiet <run-no-quiet.txt
 '
 
+test_expect_success 'maintenance.<task>.enabled' '
+	git config maintenance.gc.enabled false &&
+	git config maintenance.commit-graph.enabled true &&
+	GIT_TRACE2_EVENT="$(pwd)/run-config.txt" git maintenance run 2>err &&
+	test_subcommand ! git gc --quiet <run-config.txt &&
+	test_subcommand git commit-graph write --split --reachable --no-progress <run-config.txt
+'
+
 test_expect_success 'run --task=<task>' '
 	GIT_TRACE2_EVENT="$(pwd)/run-commit-graph.txt" \
 		git maintenance run --task=commit-graph 2>/dev/null &&