[PATCH v4 19/21] refs: add register_ref_storage_backends()

[David Turner <dturner@twopensource.com>]

This new function will register all known ref storage backends... once
there are any other than the default.  For now, it's a no-op.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 builtin/init-db.c |  3 +++
 config.c          | 25 +++++++++++++++++++++++++
 refs.c            |  8 ++++++++
 refs.h            |  2 ++
 4 files changed, 38 insertions(+)

diff --git a/builtin/init-db.c b/builtin/init-db.c
index d331ce8..4209b67 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -226,6 +226,7 @@ static int create_default_files(const char *template_path)
 	if (strcmp(ref_storage_backend, "files")) {
 		git_config_set("extensions.refStorage", ref_storage_backend);
 		git_config_set("core.repositoryformatversion", ref_storage_backend);
+		register_ref_storage_backends();
 		if (set_ref_storage_backend(ref_storage_backend))
 			die(_("Unknown ref storage backend %s"),
 			    ref_storage_backend);
@@ -503,6 +504,8 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 
 	argc = parse_options(argc, argv, prefix, init_db_options, init_db_usage, 0);
 
+	register_ref_storage_backends();
+
 	if (requested_ref_storage_backend &&
 	    !ref_storage_backend_exists(requested_ref_storage_backend))
 		die(_("Unknown ref storage backend %s"),
diff --git a/config.c b/config.c
index b95ac3a..b9ef223 100644
--- a/config.c
+++ b/config.c
@@ -11,6 +11,7 @@
 #include "strbuf.h"
 #include "quote.h"
 #include "hashmap.h"
+#include "refs.h"
 #include "string-list.h"
 #include "utf8.h"
 
@@ -1207,6 +1208,30 @@ int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 	}
 
 	if (repo_config && !access_or_die(repo_config, R_OK, 0)) {
+		char *storage = NULL;
+
+		/*
+		 * make sure we always read the ref storage config
+		 * from the extensions section on startup
+		 */
+		ret += git_config_from_file(ref_storage_backend_config,
+					    repo_config, &storage);
+
+		register_ref_storage_backends();
+		if (!storage)
+			storage = xstrdup("");
+
+		if ((!*storage) ||
+		    (!strcmp(storage, "files"))) {
+			/* default backend, nothing to do */
+			free(storage);
+		} else {
+			ref_storage_backend = storage;
+			if (set_ref_storage_backend(ref_storage_backend))
+				die(_("Unknown ref storage backend %s"),
+				    ref_storage_backend);
+		}
+
 		ret += git_config_from_file(fn, repo_config, data);
 		found += 1;
 	}
diff --git a/refs.c b/refs.c
index 715a492..e50cca0 100644
--- a/refs.c
+++ b/refs.c
@@ -1554,3 +1554,11 @@ done:
 	string_list_clear(&affected_refnames, 0);
 	return ret;
 }
+
+void register_ref_storage_backends(void) {
+	/*
+	 * No need to register the files backend; it's registered by
+	 * default. Add register_ref_storage_backend(ptr-to-backend)
+	 * entries below when you add a new backend.
+	 */
+}
diff --git a/refs.h b/refs.h
index 680a535..81aab6b 100644
--- a/refs.h
+++ b/refs.h
@@ -525,4 +525,6 @@ int ref_storage_backend_exists(const char *name);
 
 void register_ref_storage_backend(struct ref_storage_be *be);
 
+void register_ref_storage_backends(void);
+
 #endif /* REFS_H */
-- 
2.4.2.749.g730654d-twtrsrc