[PATCH] Remove empty ref directories while reading loose refs

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Empty directories in $GIT_DIR/refs increases overhead at startup.
Removing a ref does not remove its parent directories even if it's the
only file left so empty directories will be hanging around.

pack-refs was taught of cleaning up empty directories in be7c6d4
(pack-refs: remove newly empty directories - 2010-07-06), but it only
checks parent directories of packed refs only. Already empty dirs are
left untouched.

This patch removes empty directories as we see while traversing
$GIT_DIR/refs and reverts be7c6d4 because it's no longer needed.

Some directories, even if empty, are not removed:

 - refs: this one is needed to recognize a git repository
 - refs/heads and refs/tags: these are created by init-db, people may
   expect them to always be there

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 I don't think the a few extra rmdir()s from time to time at startup
 are going to cause any problems. Making delete_ref() delete empty
 directories takes more effort and probably not worth it.

 Of course this only works if people do not expect empty directories
 to stay in $GIT_DIR/refs permanently. They now may need to put .keep
 file in to keep parent directories from being removed. Would anyone
 do that?

 pack-refs.c          |   32 --------------------------------
 refs.c               |   14 +++++++++++++-
 t/t3210-pack-refs.sh |    6 ------
 3 files changed, 13 insertions(+), 39 deletions(-)

diff --git a/pack-refs.c b/pack-refs.c
index f09a054..ec9e476 100644
--- a/pack-refs.c
+++ b/pack-refs.c
@@ -60,37 +60,6 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 	return 0;
 }
 
-/*
- * Remove empty parents, but spare refs/ and immediate subdirs.
- * Note: munges *name.
- */
-static void try_remove_empty_parents(char *name)
-{
-	char *p, *q;
-	int i;
-	p = name;
-	for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
-		while (*p && *p != '/')
-			p++;
-		/* tolerate duplicate slashes; see check_refname_format() */
-		while (*p == '/')
-			p++;
-	}
-	for (q = p; *q; q++)
-		;
-	while (1) {
-		while (q > p && *q != '/')
-			q--;
-		while (q > p && *(q-1) == '/')
-			q--;
-		if (q == p)
-			break;
-		*q = '\0';
-		if (rmdir(git_path("%s", name)))
-			break;
-	}
-}
-
 /* make sure nobody touched the ref, and unlink */
 static void prune_ref(struct ref_to_prune *r)
 {
@@ -99,7 +68,6 @@ static void prune_ref(struct ref_to_prune *r)
 	if (lock) {
 		unlink_or_warn(git_path("%s", r->name));
 		unlock_ref(lock);
-		try_remove_empty_parents(r->name);
 	}
 }
 
diff --git a/refs.c b/refs.c
index b8843bb..80ebba3 100644
--- a/refs.c
+++ b/refs.c
@@ -343,6 +343,12 @@ static void get_ref_dir(struct ref_cache *refs, const char *base,
 		struct dirent *de;
 		int baselen = strlen(base);
 		char *refname = xmalloc(baselen + 257);
+		int empty_dir = 1;
+
+		if (!strcmp(base, "refs") ||
+		    !strcmp(base, "refs/heads") ||
+		    !strcmp(base, "refs/tags"))
+			empty_dir = 0;
 
 		memcpy(refname, base, baselen);
 		if (baselen && base[baselen-1] != '/')
@@ -355,8 +361,12 @@ static void get_ref_dir(struct ref_cache *refs, const char *base,
 			int namelen;
 			const char *refdir;
 
-			if (de->d_name[0] == '.')
+			if (de->d_name[0] == '.') {
+				if (de->d_name[1] != '.' || de->d_name[2])
+					empty_dir = 0;
 				continue;
+			}
+			empty_dir = 0;
 			namelen = strlen(de->d_name);
 			if (namelen > 255)
 				continue;
@@ -387,6 +397,8 @@ static void get_ref_dir(struct ref_cache *refs, const char *base,
 		}
 		free(refname);
 		closedir(dir);
+		if (empty_dir)
+			rmdir(path);
 	}
 }
 
diff --git a/t/t3210-pack-refs.sh b/t/t3210-pack-refs.sh
index cd04361..5251740 100755
--- a/t/t3210-pack-refs.sh
+++ b/t/t3210-pack-refs.sh
@@ -60,12 +60,6 @@ test_expect_success 'see if git pack-refs --prune remove ref files' '
      ! test -f .git/refs/heads/f
 '
 
-test_expect_success 'see if git pack-refs --prune removes empty dirs' '
-     git branch r/s/t &&
-     git pack-refs --all --prune &&
-     ! test -e .git/refs/heads/r
-'
-
 test_expect_success \
     'git branch g should work when git branch g/h has been deleted' \
     'git branch g/h &&
-- 
1.7.8.36.g69ee2