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, 12 insertions, 15 deletions

diff --git a/remote.c b/remote.c
index df9675cd33..59b3715120 100644
--- a/remote.c
+++ b/remote.c
@@ -2315,21 +2315,19 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb,
 	return 1;
 }
 
-static int one_local_ref(const char *refname, const char *referent UNUSED, const struct object_id *oid,
-			 int flag UNUSED,
-			 void *cb_data)
+static int one_local_ref(const struct reference *ref, void *cb_data)
 {
 	struct ref ***local_tail = cb_data;
-	struct ref *ref;
+	struct ref *local_ref;
 
 	/* we already know it starts with refs/ to get here */
-	if (check_refname_format(refname + 5, 0))
+	if (check_refname_format(ref->name + 5, 0))
 		return 0;
 
-	ref = alloc_ref(refname);
-	oidcpy(&ref->new_oid, oid);
-	**local_tail = ref;
-	*local_tail = &ref->next;
+	local_ref = alloc_ref(ref->name);
+	oidcpy(&local_ref->new_oid, ref->oid);
+	**local_tail = local_ref;
+	*local_tail = &local_ref->next;
 	return 0;
 }
 
@@ -2402,15 +2400,14 @@ struct stale_heads_info {
 	struct refspec *rs;
 };
 
-static int get_stale_heads_cb(const char *refname, const char *referent UNUSED, const struct object_id *oid,
-			      int flags, void *cb_data)
+static int get_stale_heads_cb(const struct reference *ref, void *cb_data)
 {
 	struct stale_heads_info *info = cb_data;
 	struct string_list matches = STRING_LIST_INIT_DUP;
 	struct refspec_item query;
 	int i, stale = 1;
 	memset(&query, 0, sizeof(struct refspec_item));
-	query.dst = (char *)refname;
+	query.dst = (char *)ref->name;
 
 	refspec_find_all_matches(info->rs, &query, &matches);
 	if (matches.nr == 0)
@@ -2423,7 +2420,7 @@ static int get_stale_heads_cb(const char *refname, const char *referent UNUSED,
 	 * overlapping refspecs, we need to go over all of the
 	 * matching refs.
 	 */
-	if (flags & REF_ISSYMREF)
+	if (ref->flags & REF_ISSYMREF)
 		goto clean_exit;
 
 	for (i = 0; stale && i < matches.nr; i++)
@@ -2431,8 +2428,8 @@ static int get_stale_heads_cb(const char *refname, const char *referent UNUSED,
 			stale = 0;
 
 	if (stale) {
-		struct ref *ref = make_linked_ref(refname, &info->stale_refs_tail);
-		oidcpy(&ref->new_oid, oid);
+		struct ref *linked_ref = make_linked_ref(ref->name, &info->stale_refs_tail);
+		oidcpy(&linked_ref->new_oid, ref->oid);
 	}
 
 clean_exit: