b2b6811451
When the completion script lists short refs it does so using the 'git
for-each-ref' format 'refname:short', which makes sure that all listed
refs are unambiguous. While disambiguating refs is technically
correct in this case, as opposed to the cases discussed in the
previous patch, this disambiguation involves several stat() syscalls
for each ref, thus, unfortunately, comes at a steep cost especially on
Windows and/or when there are a lot of refs to be listed. A user of
Git for Windows reported[1] 'git checkout <TAB>' taking ~11 seconds in
a repository with just about 4000 refs.
However, it's questionable whether ambiguous refs are really that bad
to justify that much extra cost:
- Ambiguous refs are not that common,
- even if a repository contains ambiguous refs, they only hurt when
the user actually happens to want to do something with one of the
ambiguous refs, and
- the issue can be easily circumvented by renaming those ambiguous
refs.
- On the other hand, apparently not that many refs are needed to
make refs completion unacceptably slow on Windows,
- and this slowness bites each and every time the user attempts refs
completion, even when the repository doesn't contain any ambiguous
refs.
- Furthermore, circumventing the issue might not be possible or
might be considerably more difficult and requires various
trade-offs (e.g. working in a repository with only a few selected
important refs while keeping a separate repository with all refs
for reference).
Arguably, in this case the benefits of technical correctness are
rather minor compared to the price we pay for it, and we are better
off opting for performance over correctness.
Use the 'git for-each-ref' format 'refname:strip=2' to list short refs
to spare the substantial cost of disambiguating.
This speeds up refs completion considerably. Uniquely completing a
branch in a repository with 100k local branches, all packed, best of
five:
On Linux, before:
$ time __git_complete_refs --cur=maste
real 0m1.662s
user 0m1.368s
sys 0m0.296s
After:
real 0m0.831s
user 0m0.808s
sys 0m0.028s
On Windows, before:
real 0m12.457s
user 0m1.016s
sys 0m0.092s
After:
real 0m1.480s
user 0m1.031s
sys 0m0.060s
[1] - https://github.com/git-for-windows/git/issues/524
Signed-off-by: SZEDER Gábor <szeder.dev@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 http://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-.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://public-inbox.org/git, http://marc.info/?l=git and other archival sites.
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