scalar reconfigure: add --maintenance=<mode> option

When users want to enable the latest and greatest configuration options
recommended by Scalar after a Git upgrade, 'scalar reconfigure --all' is
a great option that iterates over all repos in the multi-valued
'scalar.repos' config key.

However, this feature previously forced users to enable background
maintenance. In some environments this is not preferred.

Add a new --maintenance=<mode> option to 'scalar reconfigure' that
provides options for enabling (default), disabling, or leaving
background maintenance config as-is.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/scalar.adoc

@@ -14,7 +14,7 @@ scalar list
 scalar register [--[no-]maintenance] [<enlistment>]
 scalar unregister [<enlistment>]
 scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
-scalar reconfigure [ --all | <enlistment> ]
+scalar reconfigure [--maintenance=<mode>] [ --all | <enlistment> ]
 scalar diagnose [<enlistment>]
 scalar delete <enlistment>
 
@@ -160,8 +160,19 @@ After a Scalar upgrade, or when the configuration of a Scalar enlistment
 was somehow corrupted or changed by mistake, this subcommand allows to
 reconfigure the enlistment.
 
-With the `--all` option, all enlistments currently registered with Scalar
+--all::
-will be reconfigured. Use this option after each Scalar upgrade.
+	When `--all` is specified, reconfigure all enlistments currently
+	registered with Scalar by the `scalar.repo` config key. Use this
+	option after each upgrade to get the latest features.
+
+--maintenance=<mode>::
+	By default, Scalar configures the enlistment to use Git's
+	background maintenance feature; this is the same as using the
+	`--maintenance=enable` value for this option. Use the
+	`--maintenance=disable` to remove each considered enlistment
+	from background maintenance. Use `--maitnenance=keep' to leave
+	the background maintenance configuration untouched for These
+	repositories.
 
 Diagnose
 ~~~~~~~~

scalar.c

@@ -668,13 +668,19 @@ static int remove_deleted_enlistment(struct strbuf *path)
 static int cmd_reconfigure(int argc, const char **argv)
 {
 	int all = 0;
+	const char *maintenance_str = NULL;
+	int maintenance = 1; /* Enable maintenance by default. */
+
 	struct option options[] = {
 		OPT_BOOL('a', "all", &all,
 			 N_("reconfigure all registered enlistments")),
+		OPT_STRING(0, "maintenance", &maintenance_str,
+			 N_("<mode>"),
+			 N_("signal how to adjust background maintenance")),
 		OPT_END(),
 	};
 	const char * const usage[] = {
-		N_("scalar reconfigure [--all | <enlistment>]"),
+		N_("scalar reconfigure [--maintenance=<mode>] [--all | <enlistment>]"),
 		NULL
 	};
 	struct string_list scalar_repos = STRING_LIST_INIT_DUP;
@@ -694,6 +700,18 @@ static int cmd_reconfigure(int argc, const char **argv)
 		usage_msg_opt(_("--all or <enlistment>, but not both"),
 			      usage, options);
 
+	if (maintenance_str) {
+		if (!strcmp(maintenance_str, "enable"))
+			maintenance = 1;
+		else if (!strcmp(maintenance_str, "disable"))
+			maintenance = 0;
+		else if (!strcmp(maintenance_str, "keep"))
+			maintenance = -1;
+		else
+			die(_("unknown mode for --maintenance option: %s"),
+			    maintenance_str);
+	}
+
 	git_config(get_scalar_repos, &scalar_repos);
 
 	for (size_t i = 0; i < scalar_repos.nr; i++) {
@@ -758,7 +776,8 @@ static int cmd_reconfigure(int argc, const char **argv)
 		the_repository = old_repo;
 		repo_clear(&r);
 
-		if (toggle_maintenance(1) >= 0)
+		if (maintenance >= 0 &&
+		    toggle_maintenance(maintenance) >= 0)
 			succeeded = 1;
 
 loop_end:

t/t9210-scalar.sh

@@ -210,7 +210,18 @@ test_expect_success 'scalar reconfigure' '
 	GIT_TRACE2_EVENT="$(pwd)/reconfigure" scalar reconfigure -a &&
 	test_path_is_file one/src/cron.txt &&
 	test true = "$(git -C one/src config core.preloadIndex)" &&
-	test_subcommand git maintenance start <reconfigure
+	test_subcommand git maintenance start <reconfigure &&
+	test_subcommand ! git maintenance unregister --force <reconfigure &&
+
+	GIT_TRACE2_EVENT="$(pwd)/reconfigure-maint-disable" \
+		scalar reconfigure -a --maintenance=disable &&
+	test_subcommand ! git maintenance start <reconfigure-maint-disable &&
+	test_subcommand git maintenance unregister --force <reconfigure-maint-disable &&
+
+	GIT_TRACE2_EVENT="$(pwd)/reconfigure-maint-keep" \
+		scalar reconfigure --maintenance=keep -a &&
+	test_subcommand ! git maintenance start <reconfigure-maint-keep &&
+	test_subcommand ! git maintenance unregister --force <reconfigure-maint-keep
 '
 
 test_expect_success 'scalar reconfigure --all with includeIf.onbranch' '