apply: fix an incomplete comment in check_patch()

This check is not only about type-change (for which it would be
sufficient to check only was_deleted()) but is also about a swap
rename.  Otherwise to_be_deleted() check is not justified.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -3218,16 +3218,22 @@ static int check_patch(struct patch *patch)
 		return status;
 	old_name = patch->old_name;
 
+	/*
+	 * A type-change diff is always split into a patch to delete
+	 * old, immediately followed by a patch to create new (see
+	 * diff.c::run_diff()); in such a case it is Ok that the entry
+	 * to be deleted by the previous patch is still in the working
+	 * tree and in the index.
+	 *
+	 * A patch to swap-rename between A and B would first rename A
+	 * to B and then rename B to A.  While applying the first one,
+	 * the presense of B should not stop A from getting renamed to
+	 * B; ask to_be_deleted() about the later rename.  Removal of
+	 * B and rename from A to B is handled the same way by asking
+	 * was_deleted().
+	 */
 	if ((tpatch = in_fn_table(new_name)) &&
-			(was_deleted(tpatch) || to_be_deleted(tpatch)))
-		/*
-		 * A type-change diff is always split into a patch to
-		 * delete old, immediately followed by a patch to
-		 * create new (see diff.c::run_diff()); in such a case
-		 * it is Ok that the entry to be deleted by the
-		 * previous patch is still in the working tree and in
-		 * the index.
-		 */
+	    (was_deleted(tpatch) || to_be_deleted(tpatch)))
 		ok_if_exists = 1;
 	else
 		ok_if_exists = 0;