free ref string returned by dwim_ref

A call to "dwim_ref(name, len, flags, &ref)" will allocate a
new string in "ref" to return the exact ref we found. We do
not consistently free it in all code paths, leading to small
leaks. The worst is in get_sha1_basic, which may be called
many times (e.g., by "cat-file --batch"), though it is
relatively unlikely, as it only triggers on a bogus reflog
specification.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rev-parse.c

@@ -150,6 +150,7 @@ static void show_rev(int type, const unsigned char *sha1, const char *name)
 				error("refname '%s' is ambiguous", name);
 				break;
 			}
+			free(full);
 		} else {
 			show_with_type(type, name);
 		}