maintenance: use 'incremental' strategy by default

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.

To make it simple for users to start background maintenance with a
recommended schedlue, update the 'maintenance.strategy' config option in
both the 'register' and 'start' subcommands. This allows users to
customize beyond the defaults using individual
'maintenance.<task>.schedule' options, but also the user can opt-out of
this strategy using 'maintenance.strategy=none'.

Helped-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-maintenance.txt

@@ -37,6 +37,23 @@ register::
 	`maintenance.<task>.schedule`. The tasks that are enabled are safe
 	for running in the background without disrupting foreground
 	processes.
++
+The `register` subcomand will also set the `maintenance.strategy` config
+value to `incremental`, if this value is not previously set. The
+`incremental` strategy uses the following schedule for each maintenance
+task:
++
+--
+* `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

builtin/gc.c

@@ -1434,6 +1434,7 @@ static int maintenance_run(int argc, const char **argv, const char *prefix)
 
 static int maintenance_register(void)
 {
+	char *config_value;
 	struct child_process config_set = CHILD_PROCESS_INIT;
 	struct child_process config_get = CHILD_PROCESS_INIT;
 
@@ -1441,6 +1442,15 @@ static int maintenance_register(void)
 	if (!the_repository || !the_repository->gitdir)
 		return 0;
 
+	/* Disable foreground maintenance */
+	git_config_set("maintenance.auto", "false");
+
+	/* Set maintenance strategy, if unset */
+	if (!git_config_get_string("maintenance.strategy", &config_value))
+		free(config_value);
+	else
+		git_config_set("maintenance.strategy", "incremental");
+
 	config_get.git_cmd = 1;
 	strvec_pushl(&config_get.args, "config", "--global", "--get", "maintenance.repo",
 		     the_repository->worktree ? the_repository->worktree

t/t7900-maintenance.sh

@@ -354,11 +354,14 @@ 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
@@ -392,4 +395,13 @@ test_expect_success 'start preserves existing schedule' '
 	grep "Important information!" cron.txt
 '
 
+test_expect_success 'register preserves existing strategy' '
+	git config maintenance.strategy none &&
+	git maintenance register &&
+	test_config maintenance.strategy none &&
+	git config --unset maintenance.strategy &&
+	git maintenance register &&
+	test_config maintenance.strategy incremental
+'
+
 test_done