refs: record the ref_store in ref_cache, not ref_dir

Instead of keeping a pointer to the `ref_store` in every `ref_dir`
entry, store it once in `struct ref_cache`, and change `struct
ref_dir` to include a pointer to its containing `ref_cache` instead.
This makes it easier to add to the information that is accessible from
a `ref_dir` without increasing the size of every `ref_dir` instance.

Note that previously, every `ref_dir` pointed at the containing
`files_ref_store` regardless of whether it was a part of the loose or
packed reference cache. Now we have to be sure to initialize the
instances to point at the correct containing `ref_cache`. So change
`create_dir_entry()` to take a `ref_cache` parameter, and change its
callers to pass the correct `ref_cache` depending on the purpose of
the new `dir_entry`.

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

3 files changed, 16 insertions, 11 deletions

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 840a0869a..1ed3a30d8 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -432,7 +432,7 @@ static void add_packed_ref(struct files_ref_store *refs,
  */
 void read_loose_refs(const char *dirname, struct ref_dir *dir)
 {
-	struct files_ref_store *refs = dir->ref_store;
+	struct files_ref_store *refs = dir->cache->ref_store;
 	DIR *d;
 	struct dirent *de;
 	int dirnamelen = strlen(dirname);
@@ -468,7 +468,7 @@ void read_loose_refs(const char *dirname, struct ref_dir *dir)
 		} else if (S_ISDIR(st.st_mode)) {
 			strbuf_addch(&refname, '/');
 			add_entry_to_dir(dir,
-					 create_dir_entry(refs, refname.buf,
+					 create_dir_entry(dir->cache, refname.buf,
 							  refname.len, 1));
 		} else {
 			if (!refs_resolve_ref_unsafe(&refs->base,
@@ -525,7 +525,7 @@ static struct ref_dir *get_loose_refs(struct files_ref_store *refs)
 		 * lazily):
 		 */
 		add_entry_to_dir(get_ref_dir(refs->loose->root),
-				 create_dir_entry(refs, "refs/", 5, 1));
+				 create_dir_entry(refs->loose, "refs/", 5, 1));
 	}
 	return get_ref_dir(refs->loose->root);
 }
diff --git a/refs/ref-cache.c b/refs/ref-cache.c
index bf911028c..96da09478 100644
--- a/refs/ref-cache.c
+++ b/refs/ref-cache.c
@@ -36,7 +36,7 @@ struct ref_dir *get_ref_dir(struct ref_entry *entry)
 			int pos = search_ref_dir(dir, "refs/bisect/", 12);
 			if (pos < 0) {
 				struct ref_entry *child_entry;
-				child_entry = create_dir_entry(dir->ref_store,
+				child_entry = create_dir_entry(dir->cache,
 							       "refs/bisect/",
 							       12, 1);
 				add_entry_to_dir(dir, child_entry);
@@ -67,7 +67,8 @@ struct ref_cache *create_ref_cache(struct files_ref_store *refs)
 {
 	struct ref_cache *ret = xcalloc(1, sizeof(*ret));
 
-	ret->root = create_dir_entry(refs, "", 0, 1);
+	ret->ref_store = refs;
+	ret->root = create_dir_entry(ret, "", 0, 1);
 	return ret;
 }
 
@@ -104,13 +105,14 @@ static void clear_ref_dir(struct ref_dir *dir)
 	dir->entries = NULL;
 }
 
-struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
+struct ref_entry *create_dir_entry(struct ref_cache *cache,
 				   const char *dirname, size_t len,
 				   int incomplete)
 {
 	struct ref_entry *direntry;
+
 	FLEX_ALLOC_MEM(direntry, name, dirname, len);
-	direntry->u.subdir.ref_store = ref_store;
+	direntry->u.subdir.cache = cache;
 	direntry->flag = REF_DIR | (incomplete ? REF_INCOMPLETE : 0);
 	return direntry;
 }
@@ -181,7 +183,7 @@ static struct ref_dir *search_for_subdir(struct ref_dir *dir,
 		 * therefore, create an empty record for it but mark
 		 * the record complete.
 		 */
-		entry = create_dir_entry(dir->ref_store, subdirname, len, 0);
+		entry = create_dir_entry(dir->cache, subdirname, len, 0);
 		add_entry_to_dir(dir, entry);
 	} else {
 		entry = dir->entries[entry_index];
diff --git a/refs/ref-cache.h b/refs/ref-cache.h
index da5388c13..83051854f 100644
--- a/refs/ref-cache.h
+++ b/refs/ref-cache.h
@@ -3,6 +3,9 @@
 
 struct ref_cache {
 	struct ref_entry *root;
+
+	/* A pointer to the files_ref_store whose cache this is: */
+	struct files_ref_store *ref_store;
 };
 
 /*
@@ -66,8 +69,8 @@ struct ref_dir {
 	 */
 	int sorted;
 
-	/* A pointer to the files_ref_store that contains this ref_dir. */
-	struct files_ref_store *ref_store;
+	/* The ref_cache containing this entry: */
+	struct ref_cache *cache;
 
 	struct ref_entry **entries;
 };
@@ -161,7 +164,7 @@ struct ref_dir *get_ref_dir(struct ref_entry *entry);
  * dirname is the name of the directory with a trailing slash (e.g.,
  * "refs/heads/") or "" for the top-level directory.
  */
-struct ref_entry *create_dir_entry(struct files_ref_store *ref_store,
+struct ref_entry *create_dir_entry(struct ref_cache *cache,
 				   const char *dirname, size_t len,
 				   int incomplete);