refs: introduce wrapper struct for `each_ref_fn`

The `each_ref_fn` callback function type is used across our code base
for several different functions that iterate through reference. There's
a bunch of callbacks implementing this type, which makes any changes to
the callback signature extremely noisy. An example of the required churn
is e8207717f1 (refs: add referent to each_ref_fn, 2024-08-09): adding a
single argument required us to change 48 files.

It was already proposed back then [1] that we might want to introduce a
wrapper structure to alleviate the pain going forward. While this of
course requires the same kind of global refactoring as just introducing
a new parameter, it at least allows us to more change the callback type
afterwards by just extending the wrapper structure.

One counterargument to this refactoring is that it makes the structure
more opaque. While it is obvious which callsites need to be fixed up
when we change the function type, it's not obvious anymore once we use
a structure. That being said, we only have a handful of sites that
actually need to populate this wrapper structure: our ref backends,
"refs/iterator.c" as well as very few sites that invoke the iterator
callback functions directly.

Introduce this wrapper structure so that we can adapt the iterator
interfaces more readily.

[1]: <ZmarVcF5JjsZx0dl@tanuki>

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

1 files changed, 8 insertions, 9 deletions

diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 74512e54a3..615f7d1aae 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -339,10 +339,9 @@ static int cmp_by_tag_and_age(const void *a_, const void *b_)
 	return a->taggerdate != b->taggerdate;
 }
 
-static int name_ref(const char *path, const char *referent UNUSED, const struct object_id *oid,
-		    int flags UNUSED, void *cb_data)
+static int name_ref(const struct reference *ref, void *cb_data)
 {
-	struct object *o = parse_object(the_repository, oid);
+	struct object *o = parse_object(the_repository, ref->oid);
 	struct name_ref_data *data = cb_data;
 	int can_abbreviate_output = data->tags_only && data->name_only;
 	int deref = 0;
@@ -350,14 +349,14 @@ static int name_ref(const char *path, const char *referent UNUSED, const struct
 	struct commit *commit = NULL;
 	timestamp_t taggerdate = TIME_MAX;
 
-	if (data->tags_only && !starts_with(path, "refs/tags/"))
+	if (data->tags_only && !starts_with(ref->name, "refs/tags/"))
 		return 0;
 
 	if (data->exclude_filters.nr) {
 		struct string_list_item *item;
 
 		for_each_string_list_item(item, &data->exclude_filters) {
-			if (subpath_matches(path, item->string) >= 0)
+			if (subpath_matches(ref->name, item->string) >= 0)
 				return 0;
 		}
 	}
@@ -378,7 +377,7 @@ static int name_ref(const char *path, const char *referent UNUSED, const struct
 			 * shouldn't stop when seeing 'refs/tags/v1.4' matches
 			 * 'refs/tags/v*'.  We should show it as 'v1.4'.
 			 */
-			switch (subpath_matches(path, item->string)) {
+			switch (subpath_matches(ref->name, item->string)) {
 			case -1: /* did not match */
 				break;
 			case 0: /* matched fully */
@@ -406,13 +405,13 @@ static int name_ref(const char *path, const char *referent UNUSED, const struct
 	}
 	if (o && o->type == OBJ_COMMIT) {
 		commit = (struct commit *)o;
-		from_tag = starts_with(path, "refs/tags/");
+		from_tag = starts_with(ref->name, "refs/tags/");
 		if (taggerdate == TIME_MAX)
 			taggerdate = commit->date;
 	}
 
-	add_to_tip_table(oid, path, can_abbreviate_output, commit, taggerdate,
-			 from_tag, deref);
+	add_to_tip_table(ref->oid, ref->name, can_abbreviate_output,
+			 commit, taggerdate, from_tag, deref);
 	return 0;
 }