Merge branch 'js/read-tree' into js/c-merge-recursive

* js/read-tree: (107 commits)
  read-tree: move merge functions to the library
  read-trees: refactor the unpack_trees() part
  tar-tree: illustrate an obscure feature better
  git.c: allow alias expansion without a git directory
  setup_git_directory_gently: do not barf when GIT_DIR is given.
  Build on Debian GNU/kFreeBSD
  Call setup_git_directory() much earlier
  Call setup_git_directory() early
  Display an error from update-ref if target ref name is invalid.
  Fix http-fetch
  t4103: fix binary patch application test.
  git-apply -R: binary patches are irreversible for now.
  Teach git-apply about '-R'
  Makefile: ssh-pull.o depends on ssh-fetch.c
  log and diff family: honor config even from subdirectories
  git-reset: detect update-ref error and report it.
  lost-found: use fsck-objects --full
  Teach git-http-fetch the --stdin switch
  Teach git-local-fetch the --stdin switch
  Make pull() support fetching multiple targets at once
  ...

1 files changed, 5 insertions, 0 deletions

diff --git a/refs.c b/refs.c
index 56db394459..02850b6908 100644
--- a/refs.c
+++ b/refs.c
@@ -294,6 +294,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *path,
 	int plen,
 	const unsigned char *old_sha1, int mustexist)
 {
+	const char *orig_path = path;
 	struct ref_lock *lock;
 	struct stat st;
 
@@ -303,7 +304,11 @@ static struct ref_lock *lock_ref_sha1_basic(const char *path,
 	plen = strlen(path) - plen;
 	path = resolve_ref(path, lock->old_sha1, mustexist);
 	if (!path) {
+		int last_errno = errno;
+		error("unable to resolve reference %s: %s",
+			orig_path, strerror(errno));
 		unlock_ref(lock);
+		errno = last_errno;
 		return NULL;
 	}
 	lock->lk = xcalloc(1, sizeof(struct lock_file));