xdl_merge(): fix thinko

If one side's block (of changed lines) ends later than the other
side's block, the former should be tested against the next block
of the other side, not vice versa.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

xdiff/xmerge.c

@@ -318,13 +318,13 @@ static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
 			xscr1->i1 = i2;
 			xscr1->i2 += xscr1->chg2;
 			xscr1->chg2 = 0;
-			xscr1 = xscr1->next;
+			xscr2 = xscr2->next;
 		} else if (i2 > i1) {
 			xscr2->chg1 -= i2 - i1;
 			xscr2->i1 = i1;
 			xscr2->i2 += xscr2->chg2;
 			xscr2->chg2 = 0;
-			xscr2 = xscr2->next;
+			xscr1 = xscr1->next;
 		} else {
 			xscr1 = xscr1->next;
 			xscr2 = xscr2->next;