diff options
authorJeff King <>2016-01-12 21:45:09 (GMT)
committerJunio C Hamano <>2016-01-13 17:05:42 (GMT)
commit2859dcd4c8605a5b9cf35efb815418ea8892658b (patch)
parent6294dcb49fb2654993fbc132f1b49443adfe4c87 (diff)
lock_ref_sha1_basic: handle REF_NODEREF with invalid refs
We sometimes call lock_ref_sha1_basic with REF_NODEREF to operate directly on a symbolic ref. This is used, for example, to move to a detached HEAD, or when updating the contents of HEAD via checkout or symbolic-ref. However, the first step of the function is to resolve the refname to get the "old" sha1, and we do so without telling resolve_ref_unsafe() that we are only interested in the symref. As a result, we may detect a problem there not with the symref itself, but with something it points to. The real-world example I found (and what is used in the test suite) is a HEAD pointing to a ref that cannot exist, because it would cause a directory/file conflict with other existing refs. This situation is somewhat broken, of course, as trying to _commit_ on that HEAD would fail. But it's not explicitly forbidden, and we should be able to move away from it. However, neither "git checkout" nor "git symbolic-ref" can do so. We try to take the lock on HEAD, which is pointing to a non-existent ref. We bail from resolve_ref_unsafe() with errno set to EISDIR, and the lock code thinks we are attempting to create a d/f conflict. Of course we're not. The problem is that the lock code has no idea what level we were at when we got EISDIR, so trying to diagnose or remove empty directories for HEAD is not useful. To make things even more complicated, we only get EISDIR in the loose-ref case. If the refs are packed, the resolution may "succeed", giving us the pointed-to ref in "refname", but a null oid. Later, we say "ah, the null oid means we are creating; let's make sure there is room for it", but mistakenly check against the _resolved_ refname, not the original. We can fix this by making two tweaks: 1. Call resolve_ref_unsafe() with RESOLVE_REF_NO_RECURSE when REF_NODEREF is set. This means any errors we get will be from the orig_refname, and we can act accordingly. We already do this in the REF_DELETING case, but we should do it for update, too. 2. If we do get a "refname" return from resolve_ref_unsafe(), even with RESOLVE_REF_NO_RECURSE it may be the name of the ref pointed-to by a symref. We already normalize this back to orig_refname before taking the lockfile, but we need to do so before the null_oid check. While we're rearranging the REF_NODEREF handling, we can also bump the initialization of lflags to the top of the function, where we are setting up other flags. This saves us from having yet another conditional block on REF_NODEREF just to set it later. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
3 files changed, 50 insertions, 9 deletions
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 69c3ecf..81c92b4 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1887,7 +1887,8 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
const char *orig_refname = refname;
struct ref_lock *lock;
int last_errno = 0;
- int type, lflags;
+ int type;
+ int lflags = 0;
int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
int resolve_flags = 0;
int attempts_remaining = 3;
@@ -1898,10 +1899,11 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
if (mustexist)
resolve_flags |= RESOLVE_REF_READING;
- if (flags & REF_DELETING) {
+ if (flags & REF_DELETING)
resolve_flags |= RESOLVE_REF_ALLOW_BAD_NAME;
- if (flags & REF_NODEREF)
- resolve_flags |= RESOLVE_REF_NO_RECURSE;
+ if (flags & REF_NODEREF) {
+ resolve_flags |= RESOLVE_REF_NO_RECURSE;
+ lflags |= LOCK_NO_DEREF;
refname = resolve_ref_unsafe(refname, resolve_flags,
@@ -1937,6 +1939,10 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
goto error_return;
+ if (flags & REF_NODEREF)
+ refname = orig_refname;
* If the ref did not exist and we are creating it, make sure
* there is no existing packed ref whose name begins with our
@@ -1952,11 +1958,6 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
lock->lk = xcalloc(1, sizeof(struct lock_file));
- lflags = 0;
- if (flags & REF_NODEREF) {
- refname = orig_refname;
- lflags |= LOCK_NO_DEREF;
- }
lock->ref_name = xstrdup(refname);
lock->orig_ref_name = xstrdup(orig_refname);
strbuf_git_path(&ref_file, "%s", refname);
diff --git a/t/ b/t/
index 5db876c..a713766 100755
--- a/t/
+++ b/t/
@@ -122,4 +122,11 @@ test_expect_success 'symbolic-ref does not create ref d/f conflicts' '
test_must_fail git symbolic-ref refs/heads/df/conflict refs/heads/df
+test_expect_success 'symbolic-ref handles existing pointer to invalid name' '
+ head=$(git rev-parse HEAD) &&
+ git symbolic-ref HEAD refs/heads/outer &&
+ git update-ref refs/heads/outer/inner $head &&
+ git symbolic-ref HEAD refs/heads/unrelated
diff --git a/t/ b/t/
index d444d5e..c5501b0 100755
--- a/t/
+++ b/t/
@@ -25,4 +25,37 @@ test_expect_success 'checkout notices failure to lock HEAD' '
test_must_fail git checkout -b other
+test_expect_success 'create ref directory/file conflict scenario' '
+ git update-ref refs/heads/outer/inner master &&
+ # do not rely on symbolic-ref to get a known state,
+ # as it may use the same code we are testing
+ reset_to_df () {
+ echo "ref: refs/heads/outer" >.git/HEAD
+ }
+test_expect_success 'checkout away from d/f HEAD (unpacked, to branch)' '
+ reset_to_df &&
+ git checkout master
+test_expect_success 'checkout away from d/f HEAD (unpacked, to detached)' '
+ reset_to_df &&
+ git checkout --detach master
+test_expect_success 'pack refs' '
+ git pack-refs --all --prune
+test_expect_success 'checkout away from d/f HEAD (packed, to branch)' '
+ reset_to_df &&
+ git checkout master
+test_expect_success 'checkout away from d/f HEAD (packed, to detached)' '
+ reset_to_df &&
+ git checkout --detach master