002933f3fe
The previous patch made it possible to perform line-level filtering during history traversal instead of in an expensive preprocessing step, but it still requires some simpler preprocessing steps, notably topo-ordering. However, nowadays we have commit-graphs storing generation numbers, which make it possible to incrementally traverse the history in topological order, without the preparatory limit_list() and sort_in_topological_order() steps; seeb45424181e(revision.c: generation-based topo-order algorithm, 2018-11-01). This patch combines the two, so we can do both the topo-ordering and the line-level filtering during history traversal, eliminating even those simpler preprocessing steps, and thus further reducing the delay before showing the first commit modifying the given line range. The 'revs->limited' flag plays the central role in this, because, due to limitations of the current implementation, the generation number-based topo-ordering is only enabled when this flag remains unset. Line-level log, however, always sets this flag in setup_revisions() ever since the feature was introduced in12da1d1f6f(Implement line-history search (git log -L), 2013-03-28). The reason for setting 'limited' is unclear, though, because the line-level log itself doesn't directly depend on it, and it doesn't affect how the limit_list() function limits the revision range. However, there is an indirect dependency: the line-level log requires topo-ordering, and the "traditional" sort_in_topological_order() requires an already limited commit list sincee6c3505b44(Make sure we generate the whole commit list before trying to sort it topologically, 2005-07-06). The new, generation numbers-based topo-ordering doesn't require a limited commit list anymore. So don't set 'revs->limited' for line-level log, unless it is really necessary, namely: - The user explicitly requested parent rewriting, because that is still done in the line_log_filter() preprocessing step (see previous patch), which requires sort_in_topological_order() and in turn limit_list() as well. - A commit-graph file is not available or it doesn't yet contain generation numbers. In these cases we had to fall back on sort_in_topological_order() and in turn limit_list(). The existing condition with generation_numbers_enabled() has already ensured that the 'limited' flag is set in these cases; this patch just makes sure that the line-level log sets 'revs->topo_order' before that condition. While the reduced delay before showing the first commit is measurable in git.git, it takes a bigger repository to make it clearly noticable. In both cases below the line ranges were chosen so that they were modified rather close to the starting revisions, so the effect of this change is most noticable. # git.git $ time git --no-pager log -L:read_alternate_refs:sha1-file.c -1 v2.23.0 Before: real 0m0.107s user 0m0.091s sys 0m0.013s After: real 0m0.058s user 0m0.050s sys 0m0.005s # linux.git $ time git --no-pager log \ -L:build_restore_work_registers:arch/mips/mm/tlbex.c -1 v5.2 Before: real 0m1.129s user 0m1.061s sys 0m0.069s After: real 0m0.096s user 0m0.087s sys 0m0.009s Additional testing by Derrick Stolee: Since this patch improves the performance for the first result, I repeated the experiment from the previous patch on the Linux kernel repository, reporting real time here: Command: git log -L 100,200:MAINTAINERS -n 1 >/dev/null Before: 0.71 s After: 0.05 s Now, we have dropped the full topo-order of all ~910,000 commits before reporting the first result. The remaining performance improvements then are: 1. Update the parent-rewriting logic to be incremental similar to how "git log --graph" behaves. 2. Use changed-path Bloom filters to reduce the time spend in the tree-diff to see if the path(s) changed. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks