bin/xbps-fetch: fix unreachable fetch result code

This commit restores the formerly unreachable code path handling the
case where the local file is identical with the remote file.

Fixes bug introduced in 66f84a8b59

bin/xbps-fetch/main.c

@@ -166,7 +166,7 @@ main(int argc, char **argv)
 			    progname, argv[i], xbps_fetch_error_string());
 			failure = true;
 			continue;
-		} else if (rv == -1) {
+		} else if (rv == 0) {
 			fprintf(stderr, "%s: file is identical with remote.\n", argv[i]);
 			if (shasum) {
 				if (!xbps_file_sha256_raw(digest, sizeof digest, filename)) {