[PATCH 06/10] builtin/gc.c: use "unsorted_string_list_has_string()" where appropriate

[Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>]

Refactor a "do I have an element like this?" pattern added in [1] and
[2] to use unsorted_string_list_has_string() instead of a
for_each_string_list_item() loop.

A preceding commit added a "const" to the "struct string_list *"
argument of unsorted_string_list_has_string(), it'll thus play nicely
with git_config_get_const_value_multi() without needing a cast here.

1. 1ebe6b02970 (maintenance: add 'unregister --force', 2022-09-27)
2. 50a044f1e40 (gc: replace config subprocesses with API calls,
   2022-09-27)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx>
---
 builtin/gc.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 04c48638ef4..f435eda2e73 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -1467,7 +1467,6 @@ static int maintenance_register(int argc, const char **argv, const char *prefix)
 	const char *key = "maintenance.repo";
 	char *config_value;
 	char *maintpath = get_maintpath();
-	struct string_list_item *item;
 	const struct string_list *list;
 
 	argc = parse_options(argc, argv, prefix, options,
@@ -1485,14 +1484,8 @@ static int maintenance_register(int argc, const char **argv, const char *prefix)
 	else
 		git_config_set("maintenance.strategy", "incremental");
 
-	if (!git_config_get_knownkey_value_multi(key, &list)) {
-		for_each_string_list_item(item, list) {
-			if (!strcmp(maintpath, item->string)) {
-				found = 1;
-				break;
-			}
-		}
-	}
+	if (!git_config_get_knownkey_value_multi(key, &list))
+		found = unsorted_string_list_has_string(list, maintpath);
 
 	if (!found) {
 		int rc;
@@ -1532,7 +1525,6 @@ static int maintenance_unregister(int argc, const char **argv, const char *prefi
 	const char *key = "maintenance.repo";
 	char *maintpath = get_maintpath();
 	int found = 0;
-	struct string_list_item *item;
 	const struct string_list *list;
 
 	argc = parse_options(argc, argv, prefix, options,
@@ -1541,14 +1533,8 @@ static int maintenance_unregister(int argc, const char **argv, const char *prefi
 		usage_with_options(builtin_maintenance_unregister_usage,
 				   options);
 
-	if (!git_config_get_knownkey_value_multi(key, &list)) {
-		for_each_string_list_item(item, list) {
-			if (!strcmp(maintpath, item->string)) {
-				found = 1;
-				break;
-			}
-		}
-	}
+	if (!git_config_get_knownkey_value_multi(key, &list))
+		found = unsorted_string_list_has_string(list, maintpath);
 
 	if (found) {
 		int rc;
-- 
2.38.0.1251.g3eefdfb5e7a