Correct priority of lightweight tags in git-describe.

We really want to always favor an annotated tag over a lightweight
tag when describing a commit.  Unfortunately git-describe wasn't
doing this as it was favoring the depth attribute of a possible_tag
over the priority.  Now priority is the highest sort and we only
consider a lightweight tag if no annotated tags were identified.

Rather than searching for the minimum tag using a simple loop we
now sort them using a stable sort algorithm, this way the possible
tags display in order if --debug gets used.  The stable sort helps
to preseve the inherit topology/date order that we obtain during
our search loop.

This fix allows the tests in t6120-describe.sh to pass.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/builtin-describe.c b/builtin-describe.c
index 421658d3bea2121fcc1f599b8d664a6c01159b8b..e38c899251c7959720bc45cd0c63ef643d6b9580 100644 (file)
--- a/builtin-describe.c
+++ b/builtin-describe.c
@@ -22,6 +22,9 @@ static struct commit_name {
        int prio; /* annotated tag = 2, tag = 1, head = 0 */
        char path[FLEX_ARRAY]; /* more */
 } **name_array[256];
+static const char *prio_names[] = {
+       "head", "lightweight", "annotated",
+};
 
 static struct commit_name *match(struct commit *cmit)
 {
@@ -118,10 +121,24 @@ static int compare_names(const void *_a, const void *_b)
 
 struct possible_tag {
        struct commit_name *name;
-       unsigned long depth;
+       int depth;
+       int found_order;
        unsigned flag_within;
 };
 
+static int compare_pt(const void *a_, const void *b_)
+{
+       struct possible_tag *a = (struct possible_tag *)a_;
+       struct possible_tag *b = (struct possible_tag *)b_;
+       if (a->name->prio != b->name->prio)
+               return b->name->prio - a->name->prio;
+       if (a->depth != b->depth)
+               return a->depth - b->depth;
+       if (a->found_order != b->found_order)
+               return a->found_order - b->found_order;
+       return 0;
+}
+
 static void describe(const char *arg, int last_one)
 {
        unsigned char sha1[20];
@@ -129,9 +146,10 @@ static void describe(const char *arg, int last_one)
        struct commit_list *list;
        static int initialized = 0;
        struct commit_name *n;
-       struct possible_tag all_matches[MAX_TAGS], *min_match;
+       struct possible_tag all_matches[MAX_TAGS];
        unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
        unsigned long seen_commits = 0;
+       int found = 0;
 
        if (get_sha1(arg, sha1))
                die("Not a valid object name %s", arg);
@@ -171,6 +189,7 @@ static void describe(const char *arg, int last_one)
                                t->name = n;
                                t->depth = seen_commits - 1;
                                t->flag_within = 1u << match_cnt;
+                               t->found_order = found++;
                                c->object.flags |= t->flag_within;
                                if (n->prio == 2)
                                        annotated_cnt++;
@@ -205,18 +224,12 @@ static void describe(const char *arg, int last_one)
        if (!match_cnt)
                die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1));
 
-       min_match = &all_matches[0];
-       for (cur_match = 1; cur_match < match_cnt; cur_match++) {
-               struct possible_tag *t = &all_matches[cur_match];
-               if (t->depth < min_match->depth
-                       && t->name->prio >= min_match->name->prio)
-                       min_match = t;
-       }
+       qsort(all_matches, match_cnt, sizeof(all_matches[0]), compare_pt);
        if (debug) {
                for (cur_match = 0; cur_match < match_cnt; cur_match++) {
                        struct possible_tag *t = &all_matches[cur_match];
-                       fprintf(stderr, " %c %8lu %s\n",
-                               min_match == t ? '*' : ' ',
+                       fprintf(stderr, " %-11s %8d %s\n",
+                               prio_names[t->name->prio],
                                t->depth, t->name->path);
                }
                fprintf(stderr, "traversed %lu commits\n", seen_commits);
@@ -228,7 +241,7 @@ static void describe(const char *arg, int last_one)
                                sha1_to_hex(gave_up_on->object.sha1));
                }
        }
-       printf("%s-g%s\n", min_match->name->path,
+       printf("%s-g%s\n", all_matches[0].name->path,
                   find_unique_abbrev(cmit->object.sha1, abbrev));
 
        if (!last_one)