xdiff: reduce indent heuristic overhead

diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c
index 0de1ef463bf71b2021ae142a80ac5f87a03a43fc..91e98ee98690276095026154a21d7890d49ea822 100644 (file)
--- a/xdiff/xdiffi.c
+++ b/xdiff/xdiffi.c
@@ -591,6 +591,11 @@ static void measure_split(const xdfile_t *xdf, long split,
  */
 #define INDENT_WEIGHT 60
 
+/*
+ * How far do we slide a hunk at most?
+ */
+#define INDENT_HEURISTIC_MAX_SLIDING 100
+
 /*
  * Compute a badness score for the hypothetical split whose measurements are
  * stored in m. The weight factors were determined empirically using the tools and
@@ -903,7 +908,12 @@ int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
                        long shift, best_shift = -1;
                        struct split_score best_score;
 
-                       for (shift = earliest_end; shift <= g.end; shift++) {
+                       shift = earliest_end;
+                       if (g.end - groupsize - 1 > shift)
+                               shift = g.end - groupsize - 1;
+                       if (g.end - INDENT_HEURISTIC_MAX_SLIDING > shift)
+                               shift = g.end - INDENT_HEURISTIC_MAX_SLIDING;
+                       for (; shift <= g.end; shift++) {
                                struct split_measurement m;
                                struct split_score score = {0, 0};