refs: make read_raw_ref() virtual

Reference backends will be able to customize this function to implement
reference reading.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -1251,8 +1251,8 @@ static const char *resolve_ref_recursively(struct ref_store *refs,
 	for (symref_count = 0; symref_count < SYMREF_MAXDEPTH; symref_count++) {
 		unsigned int read_flags = 0;
 
-		if (read_raw_ref(refs, refname,
+		if (refs->be->read_raw_ref(refs, refname,
-				 sha1, &sb_refname, &read_flags)) {
+					   sha1, &sb_refname, &read_flags)) {
 			*flags |= read_flags;
 			if (errno != ENOENT || (resolve_flags & RESOLVE_REF_READING))
 				return NULL;

refs/files-backend.c

@@ -1349,9 +1349,9 @@ static int resolve_packed_ref(struct files_ref_store *refs,
 	return -1;
 }
 
-int read_raw_ref(struct ref_store *ref_store,
+static int files_read_raw_ref(struct ref_store *ref_store,
-		 const char *refname, unsigned char *sha1,
+			      const char *refname, unsigned char *sha1,
-		 struct strbuf *referent, unsigned int *type)
+			      struct strbuf *referent, unsigned int *type)
 {
 	struct files_ref_store *refs =
 		files_downcast(ref_store, 1, "read_raw_ref");
@@ -1623,8 +1623,8 @@ retry:
 	 * fear that its value will change.
 	 */
 
-	if (read_raw_ref(ref_store, refname,
+	if (files_read_raw_ref(ref_store, refname,
-			 lock->old_oid.hash, referent, type)) {
+			       lock->old_oid.hash, referent, type)) {
 		if (errno == ENOENT) {
 			if (mustexist) {
 				/* Garden variety missing reference. */
@@ -4019,5 +4019,7 @@ struct ref_storage_be refs_be_files = {
 	NULL,
 	"files",
 	files_ref_store_create,
-	files_transaction_commit
+	files_transaction_commit,
+
+	files_read_raw_ref
 };

refs/refs-internal.h

@@ -486,6 +486,20 @@ int do_for_each_ref_iterator(struct ref_iterator *iter,
 
 struct ref_store;
 
+/* refs backends */
+
+/*
+ * Initialize the ref_store for the specified submodule, or for the
+ * main repository if submodule == NULL. These functions should call
+ * base_ref_store_init() to initialize the shared part of the
+ * ref_store and to record the ref_store for later lookup.
+ */
+typedef struct ref_store *ref_store_init_fn(const char *submodule);
+
+typedef int ref_transaction_commit_fn(struct ref_store *refs,
+				      struct ref_transaction *transaction,
+				      struct strbuf *err);
+
 /*
  * Read a reference from the specified reference store, non-recursively.
  * Set type to describe the reference, and:
@@ -524,29 +538,17 @@ struct ref_store;
  * - in all other cases, referent will be untouched, and therefore
  *   refname will still be valid and unchanged.
  */
-int read_raw_ref(struct ref_store *ref_store,
+typedef int read_raw_ref_fn(struct ref_store *ref_store,
-		 const char *refname, unsigned char *sha1,
+			    const char *refname, unsigned char *sha1,
-		 struct strbuf *referent, unsigned int *type);
+			    struct strbuf *referent, unsigned int *type);
-
-/* refs backends */
-
-/*
- * Initialize the ref_store for the specified submodule, or for the
- * main repository if submodule == NULL. These functions should call
- * base_ref_store_init() to initialize the shared part of the
- * ref_store and to record the ref_store for later lookup.
- */
-typedef struct ref_store *ref_store_init_fn(const char *submodule);
-
-typedef int ref_transaction_commit_fn(struct ref_store *refs,
-				      struct ref_transaction *transaction,
-				      struct strbuf *err);
 
 struct ref_storage_be {
 	struct ref_storage_be *next;
 	const char *name;
 	ref_store_init_fn *init;
 	ref_transaction_commit_fn *transaction_commit;
+
+	read_raw_ref_fn *read_raw_ref;
 };
 
 extern struct ref_storage_be refs_be_files;