[PATCH v7 20/33] refs: don't dereference on rename

[David Turner <dturner@twopensource.com>]

When renaming refs, don't dereference either the origin or the destination
before renaming.

The origin does not need to be dereferenced because it is presently
forbidden to rename symbolic refs.

Not dereferencing the destination fixes a bug where renaming on top of
a broken symref would use the pointed-to ref name for the moved
reflog.

Add a test for the reflog bug.

Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 refs/files-backend.c | 15 +++++++++------
 t/t3200-branch.sh    |  9 +++++++++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 189b86e..7c557b2 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2363,7 +2363,7 @@ static int files_rename_ref(const char *oldrefname, const char *newrefname,
 			    const char *logmsg)
 {
 	unsigned char sha1[20], orig_sha1[20];
-	int flag = 0, logmoved = 0;
+	int flag = 0, logmoved = 0, resolve_flags;
 	struct ref_lock *lock;
 	struct stat loginfo;
 	int log = !lstat(git_path("logs/%s", oldrefname), &loginfo);
@@ -2373,7 +2373,8 @@ static int files_rename_ref(const char *oldrefname, const char *newrefname,
 	if (log && S_ISLNK(loginfo.st_mode))
 		return error("reflog for %s is a symlink", oldrefname);
 
-	symref = resolve_ref_unsafe(oldrefname, RESOLVE_REF_READING,
+	resolve_flags = RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE;
+	symref = resolve_ref_unsafe(oldrefname, resolve_flags,
 				    orig_sha1, &flag);
 	if (flag & REF_ISSYMREF)
 		return error("refname %s is a symbolic ref, renaming it is not supported",
@@ -2393,8 +2394,8 @@ static int files_rename_ref(const char *oldrefname, const char *newrefname,
 		goto rollback;
 	}
 
-	if (!read_ref_full(newrefname, RESOLVE_REF_READING, sha1, NULL) &&
-	    delete_ref(newrefname, sha1, REF_NODEREF)) {
+	if (!read_ref_full(newrefname, resolve_flags, sha1, NULL) &&
+	    delete_ref(newrefname, NULL, REF_NODEREF)) {
 		if (errno==EISDIR) {
 			struct strbuf path = STRBUF_INIT;
 			int result;
@@ -2418,7 +2419,8 @@ static int files_rename_ref(const char *oldrefname, const char *newrefname,
 
 	logmoved = log;
 
-	lock = lock_ref_sha1_basic(newrefname, NULL, NULL, NULL, 0, NULL, &err);
+	lock = lock_ref_sha1_basic(newrefname, NULL, NULL, NULL, REF_NODEREF,
+				   NULL, &err);
 	if (!lock) {
 		error("unable to rename '%s' to '%s': %s", oldrefname, newrefname, err.buf);
 		strbuf_release(&err);
@@ -2436,7 +2438,8 @@ static int files_rename_ref(const char *oldrefname, const char *newrefname,
 	return 0;
 
  rollback:
-	lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, NULL, 0, NULL, &err);
+	lock = lock_ref_sha1_basic(oldrefname, NULL, NULL, NULL, REF_NODEREF,
+				   NULL, &err);
 	if (!lock) {
 		error("unable to lock %s for rollback: %s", oldrefname, err.buf);
 		strbuf_release(&err);
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index a897248..144e9ce 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -79,6 +79,15 @@ test_expect_success 'git branch -m dumps usage' '
 	test_i18ngrep "branch name required" err
 '
 
+test_expect_success 'git branch -m m broken_symref should work' '
+	test_when_finished "git branch -D broken_symref" &&
+	git branch -l m &&
+	git symbolic-ref refs/heads/broken_symref refs/heads/i_am_broken &&
+	git branch -m m broken_symref &&
+	git reflog exists refs/heads/broken_symref &&
+	test_must_fail git reflog exists refs/heads/i_am_broken
+'
+
 test_expect_success 'git branch -m m m/m should work' '
 	git branch -l m &&
 	git branch -m m m/m &&
-- 
2.4.2.767.g62658d5-twtrsrc