
merge-ort was designed to minimize the amount of data needed and used, and several changes were made to diffcore-rename to take advantage of extra metadata to enable this data minimization (particularly the relevant_sources variable for skipping "irrelevant" renames). This effort obviously succeeded in drastically reducing computation times, but should also theoretically allow partial clones to download much less information. Previously, though, the "prefetch" command used in diffcore-rename had never been modified and downloaded many blobs that were unnecessary for merge-ort. This commit corrects that. When doing basename comparisons, we want to fetch only the objects that will be used for basename comparisons. If after basename fetching this leaves us with no more relevant sources (or no more destinations), then we won't need to do the full inexact rename detection and can skip downloading additional source and destination files. Even if we have to do that later full inexact rename detection, irrelevant sources are culled after basename matching and before the full inexact rename detection, so we can still avoid downloading the blobs for irrelevant sources. Rename prefetch() to inexact_prefetch(), and introduce a new basename_prefetch() to take advantage of this. If we modify the testcase from commit 557ac0350d ("merge-ort: begin performance work; instrument with trace2_region_* calls", 2021-01-23) to pass --sparse --filter=blob:none to the clone command, and use the new trace2 "fetch_count" output from a few commits ago to track both the number of fetch subcommands invoked and the number of objects fetched across all those fetches, then for the mega-renames testcase we observe the following: BEFORE this commit, rebasing 35 patches: strategy # of fetches total # of objects fetched --------- ------------ -------------------------- recursive 62 11423 ort 30 11391 AFTER this commit, rebasing the same 35 patches: ort 32 63 This means that the new code only needs to download less than 2 blobs per patch being rebased. That is especially interesting given that the repository at the start only had approximately half a dozen TOTAL blobs downloaded to start with (because the default sparse-checkout of just the toplevel directory was in use). So, for this particular linux kernel testcase that involved ~26,000 renames on the upstream side (drivers/ -> pilots/) across which 35 patches were being rebased, this change reduces the number of blobs that need to be downloaded by a factor of ~180. Signed-off-by: Elijah Newren <newren@gmail.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