[PATCH v3 19/44] refs: add a backend method structure with transaction functions

[David Turner <dturner@twopensource.com>]

From: Ronnie Sahlberg <sahlberg@google.com>

Add a ref structure for backend methods. Start by adding a method pointer
for the transaction commit function.

Add a function set_refs_backend to switch between backends. The files
based backend is the default.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: David Turner <dturner@twopensource.com>
---
 refs-be-files.c | 10 ++++++++--
 refs.c          | 30 ++++++++++++++++++++++++++++++
 refs.h          | 15 +++++++++++++++
 3 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/refs-be-files.c b/refs-be-files.c
index 1308955..3050f1d 100644
--- a/refs-be-files.c
+++ b/refs-be-files.c
@@ -3225,8 +3225,8 @@ static int ref_update_reject_duplicates(struct string_list *refnames,
 	return 0;
 }
 
-int ref_transaction_commit(struct ref_transaction *transaction,
-			   struct strbuf *err)
+static int files_transaction_commit(struct ref_transaction *transaction,
+				    struct strbuf *err)
 {
 	int ret = 0, i;
 	int n = transaction->nr;
@@ -3612,3 +3612,9 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
 	unlock_ref(lock);
 	return -1;
 }
+
+struct ref_be refs_be_files = {
+	NULL,
+	"files",
+	files_transaction_commit,
+};
diff --git a/refs.c b/refs.c
index 25ad3b5..f930fe0 100644
--- a/refs.c
+++ b/refs.c
@@ -4,6 +4,29 @@
 #include "cache.h"
 #include "refs.h"
 #include "lockfile.h"
+/*
+ * We always have a files backend and it is the default.
+ */
+struct ref_be *the_refs_backend = &refs_be_files;
+/*
+ * List of all available backends
+ */
+struct ref_be *refs_backends = &refs_be_files;
+
+/*
+ * This function is used to switch to an alternate backend.
+ */
+int set_refs_backend(const char *name)
+{
+	struct ref_be *be;
+
+	for (be = refs_backends; be; be = be->next)
+		if (!strcmp(be->name, name)) {
+			the_refs_backend = be;
+			return 0;
+		}
+	return 1;
+}
 
 static int is_per_worktree_ref(const char *refname)
 {
@@ -985,3 +1008,10 @@ int ref_transaction_verify(struct ref_transaction *transaction,
 				      NULL, old_sha1,
 				      flags, NULL, err);
 }
+
+/* backend functions */
+int ref_transaction_commit(struct ref_transaction *transaction,
+			   struct strbuf *err)
+{
+	return the_refs_backend->transaction_commit(transaction, err);
+}
diff --git a/refs.h b/refs.h
index 4940ae9..419abf4 100644
--- a/refs.h
+++ b/refs.h
@@ -619,4 +619,19 @@ extern int reflog_expire(const char *refname, const unsigned char *sha1,
 			 reflog_expiry_cleanup_fn cleanup_fn,
 			 void *policy_cb_data);
 
+/* refs backends */
+typedef int ref_transaction_commit_fn(struct ref_transaction *transaction,
+				      struct strbuf *err);
+typedef void ref_transaction_free_fn(struct ref_transaction *transaction);
+
+struct ref_be {
+	struct ref_be *next;
+	const char *name;
+	ref_transaction_commit_fn *transaction_commit;
+};
+
+
+extern struct ref_be refs_be_files;
+int set_refs_backend(const char *name);
+
 #endif /* REFS_H */
-- 
2.4.2.644.g97b850b-twtrsrc