diffcore-rename.c: avoid set-but-not-used warning

Since 9d8a5a5 (diffcore-rename: refactor "too many candidates" logic,
2011-01-06), diffcore_rename() initializes num_src but does not use it
anymore.  "-Wunused-but-set-variable" in gcc-4.6 complains about this.

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diffcore-rename.c

@@ -498,7 +498,7 @@ void diffcore_rename(struct diff_options *options)
 	struct diff_queue_struct outq;
 	struct diff_score *mx;
 	int i, j, rename_count, skip_unmodified = 0;
-	int num_create, num_src, dst_cnt;
+	int num_create, dst_cnt;
 	struct progress *progress = NULL;
 
 	if (!minimum_score)
@@ -554,7 +554,6 @@ void diffcore_rename(struct diff_options *options)
 	 * files still remain as options for rename/copies!)
 	 */
 	num_create = (rename_dst_nr - rename_count);
-	num_src = rename_src_nr;
 
 	/* All done? */
 	if (!num_create)