sha1_name: remove no-op

'at' is always 0, since we can reach this point only if
!len && reflog_len, and len=at when reflog is assigned.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Felipe Contreras

sha1_name.c

@@ -464,7 +464,7 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 		struct strbuf buf = STRBUF_INIT;
 		int ret;
 		/* try the @{-N} syntax for n-th checkout */
-		ret = interpret_branch_name(str+at, &buf);
+		ret = interpret_branch_name(str, &buf);
 		if (ret > 0) {
 			/* substitute this branch name and restart */
 			return get_sha1_1(buf.buf, buf.len, sha1, 0);