Making errno when returning from verify_lock() meaningful, which
should almost but not completely fix

 * a bug in "git fetch"'s s_update_ref, which trusts the result of an
   errno == ENOTDIR check to detect D/F conflicts

ENOTDIR makes sense as a sign that a file was in the way of a
directory we wanted to create.  Should "git fetch" also look for
ENOTEMPTY or EEXIST to catch cases where a directory was in the way
of a file to be created?

Signed-off-by: Ronnie Sahlberg <sahlb...@google.com>
---
 refs.c | 4 ++++
 refs.h | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index 9ea519c..a48f805 100644
--- a/refs.c
+++ b/refs.c
@@ -1932,18 +1932,22 @@ int refname_match(const char *abbrev_name, const char 
*full_name)
        return 0;
 }
 
+/* This function should make sure errno is meaningful on error */
 static struct ref_lock *verify_lock(struct ref_lock *lock,
        const unsigned char *old_sha1, int mustexist)
 {
        if (read_ref_full(lock->ref_name, lock->old_sha1, mustexist, NULL)) {
+               int save_errno = errno;
                error("Can't verify ref %s", lock->ref_name);
                unlock_ref(lock);
+               errno = save_errno;
                return NULL;
        }
        if (hashcmp(lock->old_sha1, old_sha1)) {
                error("Ref %s is at %s but expected %s", lock->ref_name,
                        sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
                unlock_ref(lock);
+               errno = EBUSY;
                return NULL;
        }
        return lock;
diff --git a/refs.h b/refs.h
index 82cc5cb..af4fcdc 100644
--- a/refs.h
+++ b/refs.h
@@ -137,11 +137,15 @@ extern int ref_exists(const char *);
  */
 extern int peel_ref(const char *refname, unsigned char *sha1);
 
-/** Locks a "refs/" ref returning the lock on success and NULL on failure. **/
+/*
+ * Locks a "refs/" ref returning the lock on success and NULL on failure.
+ * On failure errno is set to something meaningfull.
+ */
 extern struct ref_lock *lock_ref_sha1(const char *refname, const unsigned char 
*old_sha1);
 
 /** Locks any ref (for 'HEAD' type refs). */
 #define REF_NODEREF    0x01
+/* errno is set to something meaningful on failure */
 extern struct ref_lock *lock_any_ref_for_update(const char *refname,
                                                const unsigned char *old_sha1,
                                                int flags, int *type_p);
-- 
2.0.0.438.gec92e5c

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