[PATCH 4/4] Compute accurate distances in git-describe before output.
- From
Shawn O. Pearce <spearce@spearce.org>
- Date
- Jan 27, 2007, 06:54 UTC
- Message-ID
- <20070127065421.GD10380@spearce.org>
- In-Reply-To
- <a23c4e55ca5c09f742fa2a047e45613e7797e720.1169880681.git.spearce@spearce.org>
My prior change to git-describe attempts to print the distance between the input commit and the best matching tag, but this distance was usually only an estimate as we always aborted revision walking as soon as we overflowed the configured limit on the number of possible tags (as set by --candidates).
Displaying an estimated distance is not very useful and can just be downright confusing. Most users (heck, most Git developers) don't immediately understand why this distance differs from the output of common tools such as `git rev-list | wc -l`. Even worse, the estimated distance could change in the future (including decreasing despite no rebase occuring) if we find more possible tags earlier on during traversal. (This could happen if more tags are merged into the branch between queries.) These factors basically make an estimated distance useless.
Fortunately we are usually most of the way through an accurate distance computation by the time we abort (due to reaching the current --candidates limit). This means we can simply finish counting out the revisions still in our commit queue to present the accurate distance at the end. The number of commits remaining in the commit queue is probably less than the number of commits already traversed, so finishing out the count is not likely to take very long. This final distance will then always match the output of `git rev-list | wc -l`.
We can easily reduce the total number of commits that need to be walked at the end by stopping as soon as all of the commits in the commit queue are flagged as being merged into the already selected best possible tag. If that's true then there are no remaining unseen commits which can contribute to our best possible tag's depth counter, so further traversal is useless.
Basic testing on my Mac OS X system shows there is no noticable performance difference between this accurate distance counting version of git-describe and the prior version of git-describe, at least when run on git.git.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org> --- Documentation/git-describe.txt | 2 +- builtin-describe.c | 42 +++++++++++++++++++++++++++++++++++++++- 2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/Documentation/git-describe.txt b/Documentation/git-describe.txt index b3e9276..160779a 100644 --- a/Documentation/git-describe.txt +++ b/Documentation/git-describe.txt @@ -61,7 +61,7 @@ But since my parent branch has a few commits on top of that, describe has added the number of additional commits ("+14") and the hash of the tip commit ("-g2414721") to the end. -The number of additional commits is an estimate of the number +The number of additional commits shown after the tag is the number of commits which would be displayed by "git log v1.0.4..parent". The hash suffix is "-g" + 8-char abbreviation for the tip commit of parent (which was `2414721b194453f058079d897d13c4e377f92dc6`). diff --git a/builtin-describe.c b/builtin-describe.c index 6e59e75..2ad3c16 100644 --- a/builtin-describe.c +++ b/builtin-describe.c @@ -91,6 +91,39 @@ static int compare_pt(const void *a_, const void *b_) return 0; } +static unsigned long finish_depth_computation( + struct commit_list **list, + struct possible_tag *best) +{ + unsigned long seen_commits = 0; + while (*list) { + struct commit *c = pop_commit(list); + struct commit_list *parents = c->parents; + seen_commits++; + if (c->object.flags & best->flag_within) { + struct commit_list *a = *list; + while (a) { + struct commit *i = a->item; + if (!(i->object.flags & best->flag_within)) + break; + a = a->next; + } + if (!a) + break; + } else + best->depth++; + while (parents) { + struct commit *p = parents->item; + parse_commit(p); + if (!(p->object.flags & SEEN)) + insert_by_date(p, list); + p->object.flags |= c->object.flags; + parents = parents->next; + } + } + return seen_commits; +} + static void describe(const char *arg, int last_one) { unsigned char sha1[20]; @@ -166,12 +199,19 @@ static void describe(const char *arg, int last_one) parents = parents->next; } } - free_commit_list(list); if (!match_cnt) die("cannot describe '%s'", sha1_to_hex(cmit->object.sha1)); qsort(all_matches, match_cnt, sizeof(all_matches[0]), compare_pt); + + if (gave_up_on) { + insert_by_date(gave_up_on, &list); + seen_commits--; + } + seen_commits += finish_depth_computation(&list, &all_matches[0]); + free_commit_list(list); + if (debug) { for (cur_match = 0; cur_match < match_cnt; cur_match++) { struct possible_tag *t = &all_matches[cur_match];
-- 1.5.0.rc2.g8a816