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, 19 insertions, 25 deletions

diff --git a/builtin/remote.c b/builtin/remote.c
index 8a7ed4299a..7ffc14ba15 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -570,17 +570,14 @@ struct branches_for_remote {
 	struct known_remotes *keep;
 };
 
-static int add_branch_for_removal(const char *refname,
-				  const char *referent UNUSED,
-				  const struct object_id *oid UNUSED,
-				  int flags UNUSED, void *cb_data)
+static int add_branch_for_removal(const struct reference *ref, void *cb_data)
 {
 	struct branches_for_remote *branches = cb_data;
 	struct refspec_item refspec;
 	struct known_remote *kr;
 
 	memset(&refspec, 0, sizeof(refspec));
-	refspec.dst = (char *)refname;
+	refspec.dst = (char *)ref->name;
 	if (remote_find_tracking(branches->remote, &refspec))
 		return 0;
 	free(refspec.src);
@@ -588,7 +585,7 @@ static int add_branch_for_removal(const char *refname,
 	/* don't delete a branch if another remote also uses it */
 	for (kr = branches->keep->list; kr; kr = kr->next) {
 		memset(&refspec, 0, sizeof(refspec));
-		refspec.dst = (char *)refname;
+		refspec.dst = (char *)ref->name;
 		if (!remote_find_tracking(kr->remote, &refspec)) {
 			free(refspec.src);
 			return 0;
@@ -596,16 +593,16 @@ static int add_branch_for_removal(const char *refname,
 	}
 
 	/* don't delete non-remote-tracking refs */
-	if (!starts_with(refname, "refs/remotes/")) {
+	if (!starts_with(ref->name, "refs/remotes/")) {
 		/* advise user how to delete local branches */
-		if (starts_with(refname, "refs/heads/"))
+		if (starts_with(ref->name, "refs/heads/"))
 			string_list_append(branches->skipped,
-					   abbrev_branch(refname));
+					   abbrev_branch(ref->name));
 		/* silently skip over other non-remote refs */
 		return 0;
 	}
 
-	string_list_append(branches->branches, refname);
+	string_list_append(branches->branches, ref->name);
 
 	return 0;
 }
@@ -713,18 +710,18 @@ out:
 	return error;
 }
 
-static int rename_one_ref(const char *old_refname, const char *referent,
-			  const struct object_id *oid,
-			  int flags, void *cb_data)
+static int rename_one_ref(const struct reference *ref, void *cb_data)
 {
 	struct strbuf new_referent = STRBUF_INIT;
 	struct strbuf new_refname = STRBUF_INIT;
 	struct rename_info *rename = cb_data;
+	const struct object_id *oid = ref->oid;
+	const char *referent = ref->target;
 	int error;
 
-	compute_renamed_ref(rename, old_refname, &new_refname);
+	compute_renamed_ref(rename, ref->name, &new_refname);
 
-	if (flags & REF_ISSYMREF) {
+	if (ref->flags & REF_ISSYMREF) {
 		/*
 		 * Stupidly enough `referent` is not pointing to the immediate
 		 * target of a symref, but it's the recursively resolved value.
@@ -732,25 +729,25 @@ static int rename_one_ref(const char *old_refname, const char *referent,
 		 * unborn symrefs don't have any value for the `referent` at all.
 		 */
 		referent = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
-						   old_refname, RESOLVE_REF_NO_RECURSE,
+						   ref->name, RESOLVE_REF_NO_RECURSE,
 						   NULL, NULL);
 		compute_renamed_ref(rename, referent, &new_referent);
 		oid = NULL;
 	}
 
-	error = ref_transaction_delete(rename->transaction, old_refname,
+	error = ref_transaction_delete(rename->transaction, ref->name,
 				       oid, referent, REF_NO_DEREF, NULL, rename->err);
 	if (error < 0)
 		goto out;
 
 	error = ref_transaction_update(rename->transaction, new_refname.buf, oid, null_oid(the_hash_algo),
-				       (flags & REF_ISSYMREF) ? new_referent.buf : NULL, NULL,
+				       (ref->flags & REF_ISSYMREF) ? new_referent.buf : NULL, NULL,
 				       REF_SKIP_CREATE_REFLOG | REF_NO_DEREF | REF_SKIP_OID_VERIFICATION,
 				       NULL, rename->err);
 	if (error < 0)
 		goto out;
 
-	error = rename_one_reflog(old_refname, oid, rename);
+	error = rename_one_reflog(ref->name, oid, rename);
 	if (error < 0)
 		goto out;
 
@@ -1125,19 +1122,16 @@ static void free_remote_ref_states(struct ref_states *states)
 	string_list_clear_func(&states->push, clear_push_info);
 }
 
-static int append_ref_to_tracked_list(const char *refname,
-				      const char *referent UNUSED,
-				      const struct object_id *oid UNUSED,
-				      int flags, void *cb_data)
+static int append_ref_to_tracked_list(const struct reference *ref, void *cb_data)
 {
 	struct ref_states *states = cb_data;
 	struct refspec_item refspec;
 
-	if (flags & REF_ISSYMREF)
+	if (ref->flags & REF_ISSYMREF)
 		return 0;
 
 	memset(&refspec, 0, sizeof(refspec));
-	refspec.dst = (char *)refname;
+	refspec.dst = (char *)ref->name;
 	if (!remote_find_tracking(states->remote, &refspec)) {
 		string_list_append(&states->tracked, abbrev_branch(refspec.src));
 		free(refspec.src);