--- a/mercurial/bdiff.c Thu Apr 21 21:05:26 2016 -0500
+++ b/mercurial/bdiff.c Thu Apr 21 22:04:11 2016 -0500
@@ -148,7 +148,7 @@
static int longest_match(struct line *a, struct line *b, struct pos *pos,
int a1, int a2, int b1, int b2, int *omi, int *omj)
{
- int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k;
+ int mi = a1, mj = b1, mk = 0, mb = 0, i, j, k, half = (a1 + a2) / 2;
for (i = a1; i < a2; i++) {
/* skip all lines in b after the current block */
@@ -165,8 +165,9 @@
pos[j].pos = i;
pos[j].len = k;
- /* best match so far? */
- if (k > mk || (k == mk && i <= mi)) {
+ /* best match so far? we prefer matches closer
+ to the middle to balance recursion */
+ if (k > mk || (k == mk && (i <= mi || i < half))) {
mi = i;
mj = j;
mk = k;