peel_ref(): fix return value for non-peelable, not-current reference

The old version was inconsistent: when a reference was
REF_KNOWS_PEELED but with a null peeled value, it returned non-zero
for the current reference but zero for other references.  Change the
behavior for non-current references to match that of current_ref,
which is what callers expect.  Document the behavior.

Current callers only call peel_ref() from within a for_each_ref-style
iteration and only for the current ref; therefore, the buggy code path
was never reached.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/refs.h b/refs.h
index f111024..3fc97a2 100644
--- a/refs.h
+++ b/refs.h
@@ -74,6 +74,14 @@ extern void add_packed_ref(const char *refname, const unsigned char *sha1);
 
 extern int ref_exists(const char *);
 
+/*
+ * If refname is a non-symbolic reference that refers to a tag object,
+ * and the tag can be (recursively) dereferenced to a non-tag object,
+ * store the SHA1 of the referred-to object to sha1 and return 0.  If
+ * any of these conditions are not met, return a non-zero value.
+ * Symbolic references are considered unpeelable, even if they
+ * ultimately resolve to a peelable tag.
+ */
 extern int peel_ref(const char *refname, unsigned char *sha1);
 
 /** Locks a "refs/" ref returning the lock on success and NULL on failure. **/