builtin/maintenance: introduce "worktree-prune" task

While git-gc(1) knows to prune stale worktrees, git-maintenance(1) does
not yet have a task for this cleanup. Introduce a new "worktree-prune"
task to plug this gap.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/maintenance.adoc

@@ -83,3 +83,11 @@ maintenance.reflog-expire.auto::
 	positive value implies the command should run when the number of
 	expired reflog entries in the "HEAD" reflog is at least the value of
 	`maintenance.loose-objects.auto`. The default value is 100.
+
+maintenance.worktree-prune.auto::
+	This integer config option controls how often the `worktree-prune` task
+	should be run as part of `git maintenance run --auto`. If zero, then
+	the `worktree-prune` task will not run with the `--auto` option. A
+	negative value will force the task to run every time. Otherwise, a
+	positive value implies the command should run when the number of
+	prunable worktrees exceeds the value. The default value is 1.

Documentation/git-maintenance.adoc

@@ -166,6 +166,10 @@ reflog-expire::
 	The `reflog-expire` task deletes any entries in the reflog older than the
 	expiry threshold. See linkgit:git-reflog[1] for more information.
 
+worktree-prune::
+	The `worktree-prune` task deletes stale or broken worktrees. See
+	linkit:git-worktree[1] for more information.
+
 OPTIONS
 -------
 --auto::

builtin/gc.c

@@ -43,6 +43,7 @@
 #include "hook.h"
 #include "setup.h"
 #include "trace2.h"
+#include "worktree.h"
 
 #define FAILED_RUN "failed to run %s"
 
@@ -345,6 +346,45 @@ static int maintenance_task_worktree_prune(struct maintenance_run_opts *opts UNU
 	return run_command(&prune_worktrees_cmd);
 }
 
+static int worktree_prune_condition(struct gc_config *cfg)
+{
+	struct strvec worktrees = STRVEC_INIT;
+	struct strbuf reason = STRBUF_INIT;
+	timestamp_t expiry_date;
+	int should_prune = 0;
+	int limit = 1;
+
+	git_config_get_int("maintenance.worktree-prune.auto", &limit);
+	if (limit <= 0) {
+		should_prune = limit < 0;
+		goto out;
+	}
+
+	if (parse_expiry_date(cfg->prune_worktrees_expire, &expiry_date) ||
+	    get_worktree_names(the_repository, &worktrees) < 0)
+		goto out;
+
+	for (size_t i = 0; i < worktrees.nr; i++) {
+		char *wtpath;
+
+		strbuf_reset(&reason);
+		if (should_prune_worktree(worktrees.v[i], &reason, &wtpath, expiry_date)) {
+			limit--;
+
+			if (!limit) {
+				should_prune = 1;
+				goto out;
+			}
+		}
+		free(wtpath);
+	}
+
+out:
+	strvec_clear(&worktrees);
+	strbuf_release(&reason);
+	return should_prune;
+}
+
 static int too_many_loose_objects(struct gc_config *cfg)
 {
 	/*
@@ -1465,6 +1505,7 @@ enum maintenance_task_label {
 	TASK_COMMIT_GRAPH,
 	TASK_PACK_REFS,
 	TASK_REFLOG_EXPIRE,
+	TASK_WORKTREE_PRUNE,
 
 	/* Leave as final value */
 	TASK__COUNT
@@ -1506,6 +1547,11 @@ static struct maintenance_task tasks[] = {
 		maintenance_task_reflog_expire,
 		reflog_expire_condition,
 	},
+	[TASK_WORKTREE_PRUNE] = {
+		"worktree-prune",
+		maintenance_task_worktree_prune,
+		worktree_prune_condition,
+	},
 };
 
 static int compare_tasks_by_selection(const void *a_, const void *b_)

t/t7900-maintenance.sh

@@ -493,6 +493,77 @@ test_expect_success 'reflog-expire task --auto only packs when exceeding limits'
 	test_subcommand git reflog expire --all <reflog-expire-auto.txt
 '
 
+test_expect_worktree_prune () {
+	negate=
+	if test "$1" = "!"
+	then
+		negate="!"
+		shift
+	fi
+
+	rm -f "worktree-prune.txt" &&
+	GIT_TRACE2_EVENT="$(pwd)/worktree-prune.txt" "$@" &&
+	test_subcommand $negate git worktree prune --expire 3.months.ago <worktree-prune.txt
+}
+
+test_expect_success 'worktree-prune task without --auto always prunes' '
+	test_expect_worktree_prune git maintenance run --task=worktree-prune
+'
+
+test_expect_success 'worktree-prune task --auto only prunes with prunable worktree' '
+	test_expect_worktree_prune ! git maintenance run --auto --task=worktree-prune &&
+	mkdir .git/worktrees &&
+	: >.git/worktrees/abc &&
+	test_expect_worktree_prune git maintenance run --auto --task=worktree-prune
+'
+
+test_expect_success 'worktree-prune task with --auto honors maintenance.worktree-prune.auto' '
+	# A negative value should always prune.
+	test_expect_worktree_prune git -c maintenance.worktree-prune.auto=-1 maintenance run --auto --task=worktree-prune &&
+
+	mkdir .git/worktrees &&
+	: >.git/worktrees/first &&
+	: >.git/worktrees/second &&
+	: >.git/worktrees/third &&
+
+	# Zero should never prune.
+	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=0 maintenance run --auto --task=worktree-prune &&
+	# A positive value should require at least this man prunable worktrees.
+	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=4 maintenance run --auto --task=worktree-prune &&
+	test_expect_worktree_prune git -c maintenance.worktree-prune.auto=3 maintenance run --auto --task=worktree-prune
+'
+
+test_expect_success 'worktree-prune task with --auto honors maintenance.worktree-prune.auto' '
+	# A negative value should always prune.
+	test_expect_worktree_prune git -c maintenance.worktree-prune.auto=-1 maintenance run --auto --task=worktree-prune &&
+
+	mkdir .git/worktrees &&
+	: >.git/worktrees/first &&
+	: >.git/worktrees/second &&
+	: >.git/worktrees/third &&
+
+	# Zero should never prune.
+	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=0 maintenance run --auto --task=worktree-prune &&
+	# A positive value should require at least this many prunable worktrees.
+	test_expect_worktree_prune ! git -c maintenance.worktree-prune.auto=4 maintenance run --auto --task=worktree-prune &&
+	test_expect_worktree_prune git -c maintenance.worktree-prune.auto=3 maintenance run --auto --task=worktree-prune
+'
+
+test_expect_success 'worktree-prune task honors gc.worktreePruneExpire' '
+	git worktree add worktree &&
+	rm -rf worktree &&
+
+	rm -f worktree-prune.txt &&
+	GIT_TRACE2_EVENT="$(pwd)/worktree-prune.txt" git -c gc.worktreePruneExpire=1.week.ago maintenance run --auto --task=worktree-prune &&
+	test_subcommand ! git worktree prune --expire 1.week.ago <worktree-prune.txt &&
+	test_path_is_dir .git/worktrees/worktree &&
+
+	rm -f worktree-prune.txt &&
+	GIT_TRACE2_EVENT="$(pwd)/worktree-prune.txt" git -c gc.worktreePruneExpire=now maintenance run --auto --task=worktree-prune &&
+	test_subcommand git worktree prune --expire now <worktree-prune.txt &&
+	test_path_is_missing .git/worktrees/worktree
+'
+
 test_expect_success '--auto and --schedule incompatible' '
 	test_must_fail git maintenance run --auto --schedule=daily 2>err &&
 	test_grep "at most one" err