scalar register: add --no-maintenance option

When registering a repository with Scalar to get the latest opinionated
configuration, the 'scalar register' command will also set up background
maintenance. This is a recommended feature for most user scenarios.

However, this is not always recommended in some scenarios where
background modifications may interfere with foreground activities.
Specifically, setting up a clone for use in automation may require doing
certain maintenance steps in the foreground that could become blocked by
concurrent background maintenance operations.

Allow the user to specify --no-maintenance to 'scalar register'. This
requires updating the method prototype for register_dir(), so use the
default of enabling this value when otherwise specified.

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

Documentation/scalar.adoc

@@ -11,7 +11,7 @@ SYNOPSIS
 scalar clone [--single-branch] [--branch <main-branch>] [--full-clone]
 	[--[no-]src] <url> [<enlistment>]
 scalar list
-scalar register [<enlistment>]
+scalar register [--[no-]maintenance] [<enlistment>]
 scalar unregister [<enlistment>]
 scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
 scalar reconfigure [ --all | <enlistment> ]
@@ -117,6 +117,12 @@ Note: when this subcommand is called in a worktree that is called `src/`, its
 parent directory is considered to be the Scalar enlistment. If the worktree is
 _not_ called `src/`, it itself will be considered to be the Scalar enlistment.
 
+--[no-]maintenance::
+	By default, `scalar register` configures the enlistment to use Git's
+	background maintenance feature. Use the `--no-maintenance` to skip
+	this configuration. This does not disable any maintenance that may
+	already be enabled in other ways.
+
 Unregister
 ~~~~~~~~~~
 

scalar.c

@@ -612,11 +612,14 @@ static int cmd_list(int argc, const char **argv UNUSED)
 
 static int cmd_register(int argc, const char **argv)
 {
+	int maintenance = 1;
 	struct option options[] = {
+		OPT_BOOL(0, "maintenance", &maintenance,
+			 N_("specify if background maintenance should be enabled")),
 		OPT_END(),
 	};
 	const char * const usage[] = {
-		N_("scalar register [<enlistment>]"),
+		N_("scalar register [--[no-]maintenance] [<enlistment>]"),
 		NULL
 	};
 
@@ -625,7 +628,8 @@ static int cmd_register(int argc, const char **argv)
 
 	setup_enlistment_directory(argc, argv, usage, options, NULL);
 
-	return register_dir(1);
+	/* If --no-maintenance, then leave maintenance as-is. */
+	return register_dir(maintenance);
 }
 
 static int get_scalar_repos(const char *key, const char *value,

t/t9210-scalar.sh

@@ -108,7 +108,7 @@ test_expect_success 'scalar register warns when background maintenance fails' '
 	git init register-repo &&
 	GIT_TEST_MAINT_SCHEDULER="crontab:false,launchctl:false,schtasks:false" \
 		scalar register register-repo 2>err &&
-	grep "could not turn on maintenance" err
+	grep "could not toggle maintenance" err
 '
 
 test_expect_success 'scalar unregister' '
@@ -129,6 +129,17 @@ test_expect_success 'scalar unregister' '
 	scalar unregister vanish
 '
 
+test_expect_success 'scalar register --no-maintenance' '
+	git init register-no-maint &&
+	event_log="$(pwd)/no-maint.event" &&
+	GIT_TEST_MAINT_SCHEDULER="crontab:false,launchctl:false,schtasks:false" \
+	GIT_TRACE2_EVENT="$event_log" \
+	GIT_TRACE2_EVENT_DEPTH=100 \
+		scalar register --no-maintenance register-no-maint 2>err &&
+	test_must_be_empty err &&
+	test_subcommand ! git maintenance unregister --force <no-maint.event
+'
+
 test_expect_success 'set up repository to clone' '
 	test_commit first &&
 	test_commit second &&