992f7a4fdb
For each linked worktree, Git maintains two pointers: (1)
<repo>/worktrees/<id>/gitdir which points at the linked worktree, and
(2) <worktree>/.git which points back at <repo>/worktrees/<id>. Both
pointers are absolute pathnames.
Aside from manually manipulating those raw files, it is possible to
easily "break" one or both pointers by ignoring the "git worktree move"
command and instead manually moving a linked worktree, moving the
repository, or moving both. The "git worktree repair" command was
invented to handle this case by restoring these pointers to sane values.
For the "repair" command, the "git worktree" manual page states:
Repair worktree administrative files, if possible, if they have
become corrupted or outdated due to external factors.
The "if possible" clause was chosen deliberately to convey that the
existing implementation may not be able to fix every possible breakage,
and to imply that improvements may be made to handle other types of
breakage.
A recent problem report[*] illustrates a case in which "git worktree
repair" not only fails to fix breakage, but actually causes breakage.
Specifically, if a repository / main-worktree and linked worktrees are
*copied* as a unit (rather than *moved*), then "git worktree repair" run
in the copy leaves the copy untouched but botches the pointers in the
original repository and the original worktrees.
For instance, given this directory structure:
orig/
main/ (main-worktree)
linked/ (linked worktree)
if "orig" is copied (not moved) to "dup", then immediately after the
manual copy operation:
* orig/main/.git/worktrees/linked/gitdir points at orig/linked/.git
* orig/linked/.git points at orig/main/.git/worktrees/linked
* dup/main/.git/worktrees/linked/gitdir points at orig/linked/.git
* dup/linked/.git points at orig/main/.git/worktrees/linked
So, dup/main thinks its linked worktree is orig/linked, and worktree
dup/linked thinks its repository / main-worktree is orig/main.
"git worktree repair" is reasonably simple-minded; it wants to trust
valid-looking pointers, hence doesn't try to second-guess them. In this
case, when validating dup/linked/.git, it finds a legitimate repository
pointer, orig/main/.git/worktrees/linked, thus trusts that is correct,
but does notice that gitdir in that directory doesn't point at
dup/linked/.git, so it (incorrectly) _fixes_
orig/main/.git/worktrees/linked/gitdir to point at dup/linked/.git.
Similarly, when validating dup/main/.git/worktrees/linked/gitdir, it
finds a legitimate worktree pointer, orig/linked/.git, but notices that
its .git file doesn't point back at dup/main, thus (incorrectly) _fixes_
orig/linked/.git to point at dup/main/.git/worktrees/linked. Hence, it
has modified and broken the linkage between orig/main and orig/linked
rather than fixing dup/main and dup/linked as expected.
Fix this problem by also checking if a plausible .git/worktrees/<id>
exists in the *current* repository -- not just in the repository pointed
at by the worktree's .git file -- and comparing whether they are the
same. If not, then it is likely because the repository / main-worktree
and linked worktrees were copied, so prefer the discovered plausible
pointer rather than the one from the existing .git file.
[*]: https://lore.kernel.org/git/E1sr5iF-0007zV-2k@binarylane-bailey.stuart.id.au/
Reported-by: Russell Stuart <russell+git.vger.kernel.org@stuart.id.au>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.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 and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://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