describe: when failing, tell the user about options that work

Users seem to call git-describe without reading the manpage, and then
wonder why it doesn't work with unannotated tags by default.

Make a minimal effort towards seeing if there would have been
unannotated tags, and tell the user.  Specifically, we say that --tags
could work if we found any unannotated tags.  If not, we say that
--always would have given results.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-describe.c b/builtin-describe.c
index eaa8a9d229c97ebaab9ee3aa09d2456f68cd172c..504d9b120976e7d65d4a229b251e1a006c69e715 100644 (file)
--- a/builtin-describe.c
+++ b/builtin-describe.c
@@ -96,8 +96,6 @@ static int get_name(const char *path, const unsigned char *sha1, int flag, void
        if (!all) {
                if (!prio)
                        return 0;
-               if (!tags && prio < 2)
-                       return 0;
        }
        add_to_known_names(all ? path + 5 : path + 10, commit, prio, sha1);
        return 0;
@@ -184,6 +182,7 @@ static void describe(const char *arg, int last_one)
        struct possible_tag all_matches[MAX_TAGS];
        unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
        unsigned long seen_commits = 0;
+       unsigned int unannotated_cnt = 0;
 
        if (get_sha1(arg, sha1))
                die("Not a valid object name %s", arg);
@@ -217,7 +216,9 @@ static void describe(const char *arg, int last_one)
                seen_commits++;
                n = c->util;
                if (n) {
-                       if (match_cnt < max_candidates) {
+                       if (!tags && !all && n->prio < 2) {
+                               unannotated_cnt++;
+                       } else if (match_cnt < max_candidates) {
                                struct possible_tag *t = &all_matches[match_cnt++];
                                t->name = n;
                                t->depth = seen_commits - 1;
@@ -259,7 +260,14 @@ static void describe(const char *arg, int last_one)
                        printf("%s\n", find_unique_abbrev(sha1, abbrev));
                        return;
                }
-               die("cannot describe '%s'", sha1_to_hex(sha1));
+               if (unannotated_cnt)
+                       die("No annotated tags can describe '%s'.\n"
+                           "However, there were unannotated tags: try --tags.",
+                           sha1_to_hex(sha1));
+               else
+                       die("No tags can describe '%s'.\n"
+                           "Try --always, or create some tags.",
+                           sha1_to_hex(sha1));
        }
 
        qsort(all_matches, match_cnt, sizeof(all_matches[0]), compare_pt);