name-rev: Fix non-shortest description

Uwe Kleine-König noticed that under certain circumstances, name-rev
picked a non-optimal tag.  Jeff King analyzed that name-rev only
takes into account the number of merge traversals, and then the
_last_ number in the description.

As an easy way to fix it, use a weighting factor for merge traversals:
A merge traversal is now made 65535 times more expensive than a
first-parent traversal.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Uwe Kleine-König <ukleinek@informatik.uni-freiburg.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-name-rev.c b/builtin-name-rev.c
index 61eba343ab781341a0baf127b323508a0c2af332..03083e94776234b280316978cd3f638262f41398 100644 (file)
--- a/builtin-name-rev.c
+++ b/builtin-name-rev.c
@@ -11,14 +11,17 @@ static const char name_rev_usage[] =
 
 typedef struct rev_name {
        const char *tip_name;
-       int merge_traversals;
        int generation;
+       int distance;
 } rev_name;
 
 static long cutoff = LONG_MAX;
 
+/* How many generations are maximally preferred over _one_ merge traversal? */
+#define MERGE_TRAVERSAL_WEIGHT 65535
+
 static void name_rev(struct commit *commit,
-               const char *tip_name, int merge_traversals, int generation,
+               const char *tip_name, int generation, int distance,
                int deref)
 {
        struct rev_name *name = (struct rev_name *)commit->util;
@@ -45,13 +48,11 @@ static void name_rev(struct commit *commit,
                name = xmalloc(sizeof(rev_name));
                commit->util = name;
                goto copy_data;
-       } else if (name->merge_traversals > merge_traversals ||
-                       (name->merge_traversals == merge_traversals &&
-                        name->generation > generation)) {
+       } else if (name->distance > distance) {
 copy_data:
                name->tip_name = tip_name;
-               name->merge_traversals = merge_traversals;
                name->generation = generation;
+               name->distance = distance;
        } else
                return;
 
@@ -74,11 +75,11 @@ copy_data:
                                sprintf(new_name, "%.*s^%d", len, tip_name,
                                                parent_number);
 
-                       name_rev(parents->item, new_name,
-                               merge_traversals + 1 , 0, 0);
+                       name_rev(parents->item, new_name, 0,
+                               distance + MERGE_TRAVERSAL_WEIGHT, 0);
                } else {
-                       name_rev(parents->item, tip_name, merge_traversals,
-                               generation + 1, 0);
+                       name_rev(parents->item, tip_name, generation + 1,
+                               distance + 1, 0);
                }
        }
 }