From 30b1c7ad9d64695a65c23f922e6ffd2fd35660da Mon Sep 17 00:00:00 2001 From: Benno Evers Date: Wed, 26 Feb 2020 18:48:53 +0100 Subject: describe: don't abort too early when searching tags When searching the commit graph for tag candidates, `git-describe` will stop as soon as there is only one active branch left and it already found an annotated tag as a candidate. This works well as long as all branches eventually connect back to a common root, but if the tags are found across branches with no common ancestor B o----. \ o-----o---o----x A it can happen that the search on one branch terminates prematurely because a tag was found on another, independent branch. This scenario isn't quite as obscure as it sounds, since cloning with a limited depth often introduces many independent "dead ends" into the commit graph. The help text of `git-describe` states pretty clearly that when describing a commit D, the number appended to the emitted tag X should correspond to the number of commits found by `git log X..D`. Thus, this commit modifies the stopping condition to only abort the search when only one branch is left to search *and* all current best candidates are descendants from that branch. For repositories with a single root, this condition is always true: When the search is reduced to a single active branch, the current commit must be an ancestor of *all* tag candidates. This means that in the common case, this change will have no negative performance impact since the same number of commits as before will be traversed. Signed-off-by: Benno Evers Signed-off-by: Junio C Hamano --- builtin/describe.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'builtin') diff --git a/builtin/describe.c b/builtin/describe.c index b6df81d8d0..420f4c6401 100644 --- a/builtin/describe.c +++ b/builtin/describe.c @@ -376,11 +376,25 @@ static void describe_commit(struct object_id *oid, struct strbuf *dst) if (!(c->object.flags & t->flag_within)) t->depth++; } + /* Stop if last remaining path already covered by best candidate(s) */ if (annotated_cnt && !list) { - if (debug) - fprintf(stderr, _("finished search at %s\n"), - oid_to_hex(&c->object.oid)); - break; + int best_depth = INT_MAX; + unsigned best_within = 0; + for (cur_match = 0; cur_match < match_cnt; cur_match++) { + struct possible_tag *t = &all_matches[cur_match]; + if (t->depth < best_depth) { + best_depth = t->depth; + best_within = t->flag_within; + } else if (t->depth == best_depth) { + best_within |= t->flag_within; + } + } + if ((c->object.flags & best_within) == best_within) { + if (debug) + fprintf(stderr, _("finished search at %s\n"), + oid_to_hex(&c->object.oid)); + break; + } } while (parents) { struct commit *p = parents->item; -- cgit v1.2.3