[PATCH v2 20/20] ref_transaction_commit(): clean up empty directories

From: Michael Haggerty <mhagger@alum.mit.edu>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org, Karl Moskowski <kmoskowski@me.com>,
	Jeff King <peff@peff.net>, Mike Hommey <mh@glandium.org>,
	David Turner <dturner@twopensource.com>,
	Michael Haggerty <mhagger@alum.mit.edu>
Subject: [PATCH v2 20/20] ref_transaction_commit(): clean up empty directories
Date: Thu, 25 Feb 2016 14:16:19 +0100	[thread overview]
Message-ID: <1c2176ceec2f28709ca9f16adf291c34abb00cf3.1456405699.git.mhagger@alum.mit.edu> (raw)
In-Reply-To: <cover.1456405698.git.mhagger@alum.mit.edu>

When deleting/pruning references, remove any directories that are made
empty by the deletion of loose references or of reflogs. Otherwise such
empty directories can survive forever and accumulate over time. (Even
'pack-refs', which is smart enough to remove the parent directories of
loose references that it prunes, leaves directories that were already
empty.)

And now that ref_transaction_commit() takes care of deleting the parent
directories of loose references that it prunes, we don't have to do that
in prune_ref() anymore.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/files-backend.c  | 37 +++++++++++++++++++++++++++++++------
 refs/refs-internal.h  |  9 ++++++++-
 t/t1400-update-ref.sh | 27 +++++++++++++++++++++++++++
 3 files changed, 66 insertions(+), 7 deletions(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 9ebb188..9973958 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2263,7 +2263,6 @@ static void prune_ref(struct ref_to_prune *r)
 	}
 	ref_transaction_free(transaction);
 	strbuf_release(&err);
-	try_remove_empty_parents(r->name, REMOVE_EMPTY_PARENTS_REF);
 }
 
 static void prune_refs(struct ref_to_prune *r)
@@ -3261,6 +3260,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 					ret = TRANSACTION_GENERIC_ERROR;
 					goto cleanup;
 				}
+				update->flags |= REF_DELETED_LOOSE;
 			}
 
 			if (!(update->flags & REF_ISPRUNING))
@@ -3273,16 +3273,41 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		ret = TRANSACTION_GENERIC_ERROR;
 		goto cleanup;
 	}
-	for_each_string_list_item(ref_to_delete, &refs_to_delete)
-		unlink_or_warn(git_path("logs/%s", ref_to_delete->string));
+
+	/* Delete the reflogs of any references that were deleted: */
+	for_each_string_list_item(ref_to_delete, &refs_to_delete) {
+		if (!unlink_or_warn(git_path("logs/%s", ref_to_delete->string)))
+			try_remove_empty_parents(ref_to_delete->string,
+						 REMOVE_EMPTY_PARENTS_REFLOG);
+	}
+
 	clear_loose_ref_cache(&ref_cache);
 
 cleanup:
 	transaction->state = REF_TRANSACTION_CLOSED;
 
-	for (i = 0; i < n; i++)
-		if (updates[i]->lock)
-			unlock_ref(updates[i]->lock);
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if (!update->lock)
+			continue;
+
+		if (update->flags & REF_DELETED_LOOSE) {
+			/*
+			 * The loose reference was deleted. We want to
+			 * delete any empty parent directories, but
+			 * that can only work after we have removed
+			 * the lockfile:
+			 */
+			char *path = xstrdup(update->lock->ref_name);
+			unlock_ref(update->lock);
+			try_remove_empty_parents(path, REMOVE_EMPTY_PARENTS_REF);
+			free(path);
+		} else {
+			unlock_ref(update->lock);
+		}
+	}
+
 	string_list_clear(&refs_to_delete, 0);
 	string_list_clear(&affected_refnames, 0);
 	return ret;
diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index c7dded3..dd09be1 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -43,6 +43,12 @@
  */
 
 /*
+ * Used as a flag in ref_update::flags when the loose reference has
+ * been deleted.
+ */
+#define REF_DELETED_LOOSE 0x100
+
+/*
  * Return true iff refname is minimally safe. "Safe" here means that
  * deleting a loose reference by this name will not do any damage, for
  * example by causing a file that is not a reference to be deleted.
@@ -141,7 +147,8 @@ struct ref_update {
 	unsigned char old_sha1[20];
 	/*
 	 * One or more of REF_HAVE_NEW, REF_HAVE_OLD, REF_NODEREF,
-	 * REF_DELETING, and REF_ISPRUNING:
+	 * REF_DELETING, REF_ISPRUNING, REF_NEEDS_COMMIT, and
+	 * REF_DELETED_LOOSE:
 	 */
 	unsigned int flags;
 	struct ref_lock *lock;
diff --git a/t/t1400-update-ref.sh b/t/t1400-update-ref.sh
index af1b20d..00284eb 100755
--- a/t/t1400-update-ref.sh
+++ b/t/t1400-update-ref.sh
@@ -191,6 +191,33 @@ test_expect_success \
 	 git update-ref HEAD'" $A &&
 	 test $A"' = $(cat .git/'"$m"')'
 
+test_expect_success "empty directory removal" '
+	git branch d1/d2/r1 HEAD &&
+	git branch d1/r2 HEAD &&
+	test -f .git/refs/heads/d1/d2/r1 &&
+	test -f .git/logs/refs/heads/d1/d2/r1 &&
+	git branch -d d1/d2/r1 &&
+	! test -e .git/refs/heads/d1/d2 &&
+	! test -e .git/logs/refs/heads/d1/d2 &&
+	test -f .git/refs/heads/d1/r2 &&
+	test -f .git/logs/refs/heads/d1/r2
+'
+
+test_expect_success "symref empty directory removal" '
+	git branch e1/e2/r1 HEAD &&
+	git branch e1/r2 HEAD &&
+	git checkout e1/e2/r1 &&
+	test_when_finished "git checkout master" &&
+	test -f .git/refs/heads/e1/e2/r1 &&
+	test -f .git/logs/refs/heads/e1/e2/r1 &&
+	git update-ref -d HEAD &&
+	! test -e .git/refs/heads/e1/e2 &&
+	! test -e .git/logs/refs/heads/e1/e2 &&
+	test -f .git/refs/heads/e1/r2 &&
+	test -f .git/logs/refs/heads/e1/r2 &&
+	test -f .git/logs/HEAD
+'
+
 cat >expect <<EOF
 $Z $A $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	Initial Creation
 $A $B $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150260 +0000	Switch
-- 
2.7.0
