alternates: provide helper for adding to alternates list

The submodule code wants to temporarily add an alternate
object store to our in-memory alt_odb list, but does it
manually. Let's provide a helper so it can reuse the code in
link_alt_odb_entry().

While we're adding our new add_to_alternates_memory(), let's
document add_to_alternates_file(), as the two are related.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 22 deletions

diff --git a/submodule.c b/submodule.c
index 0ef2ff4321..8b3274a9dc 100644
--- a/submodule.c
+++ b/submodule.c
@@ -123,9 +123,7 @@ void stage_updated_gitmodules(void)
 static int add_submodule_odb(const char *path)
 {
 	struct strbuf objects_directory = STRBUF_INIT;
-	struct alternate_object_database *alt_odb;
 	int ret = 0;
-	size_t alloc;
 
 	ret = strbuf_git_path_submodule(&objects_directory, path, "objects/");
 	if (ret)
@@ -134,26 +132,7 @@ static int add_submodule_odb(const char *path)
 		ret = -1;
 		goto done;
 	}
-	/* avoid adding it twice */
-	prepare_alt_odb();
-	for (alt_odb = alt_odb_list; alt_odb; alt_odb = alt_odb->next)
-		if (alt_odb->name - alt_odb->base == objects_directory.len &&
-				!strncmp(alt_odb->base, objects_directory.buf,
-					objects_directory.len))
-			goto done;
-
-	alloc = st_add(objects_directory.len, 42); /* for "12/345..." sha1 */
-	alt_odb = xmalloc(st_add(sizeof(*alt_odb), alloc));
-	alt_odb->next = alt_odb_list;
-	xsnprintf(alt_odb->base, alloc, "%s", objects_directory.buf);
-	alt_odb->name = alt_odb->base + objects_directory.len;
-	alt_odb->name[2] = '/';
-	alt_odb->name[40] = '\0';
-	alt_odb->name[41] = '\0';
-	alt_odb_list = alt_odb;
-
-	/* add possible alternates from the submodule */
-	read_info_alternates(objects_directory.buf, 0);
+	add_to_alternates_memory(objects_directory.buf);
 done:
 	strbuf_release(&objects_directory);
 	return ret;