Correct builtin-fetch to handle + in refspecs

If we are fetching to a local reference (the so called peer_ref) and
the refspec that created this ref/peer_ref association had started
with '+' we are supposed to allow a non-fast-forward update during
fetch, even if --force was not supplied on the command line.  The
builtin-fetch implementation was not honoring this setting as it
was copied from the wrong struct ref instance.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-fetch.c

@@ -217,7 +217,7 @@ static void store_updated_refs(const char *url, struct ref *ref_map)
 			strcpy(ref->name, rm->peer_ref->name);
 			hashcpy(ref->old_sha1, rm->peer_ref->old_sha1);
 			hashcpy(ref->new_sha1, rm->old_sha1);
-			ref->force = rm->force;
+			ref->force = rm->peer_ref->force;
 		}
 
 		commit = lookup_commit_reference(rm->old_sha1);