refs: make sha1 output parameter of refs_resolve_ref_unsafe() optional

Allow callers of refs_resolve_ref_unsafe() to pass NULL if they don't
need the resolved hash value.  We already allow the same for the flags
parameter.  This new leniency is inherited by the various wrappers like
resolve_ref_unsafe().

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/refs.c b/refs.c
index c30f4c36be..36439fdb54 100644
--- a/refs.c
+++ b/refs.c
@@ -1396,9 +1396,12 @@ const char *refs_resolve_ref_unsafe(struct ref_store *refs,
 				    unsigned char *sha1, int *flags)
 {
 	static struct strbuf sb_refname = STRBUF_INIT;
+	struct object_id unused_oid;
 	int unused_flags;
 	int symref_count;
 
+	if (!sha1)
+		sha1 = unused_oid.hash;
 	if (!flags)
 		flags = &unused_flags;