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git-commit-vandalism/Documentation/git-worktree.txt
Eric Sunshine cf76baea41 worktree: teach repair to fix multi-directional breakage 
`git worktree repair` knows how to repair the two-way links between the
repository and a worktree as long as a link in one or the other
direction is sound. For instance, if a linked worktree is moved (without
using `git worktree move`), repair is possible because the worktree
still knows the location of the repository even though the repository no
longer knows where the worktree is. Similarly, if the repository is
moved, repair is possible since the repository still knows the locations
of the worktrees even though the worktrees no longer know where the
repository is.

However, if both the repository and the worktrees are moved, then links
are severed in both directions, and no repair is possible. This is the
case even when the new worktree locations are specified as arguments to
`git worktree repair`. The reason for this limitation is twofold. First,
when `repair` consults the worktree's gitfile (/path/to/worktree/.git)
to determine the corresponding <repo>/worktrees/<id>/gitdir file to fix,
<repo> is the old path to the repository, thus it is unable to fix the
`gitdir` file at its new location since it doesn't know where it is.
Second, when `repair` consults <repo>/worktrees/<id>/gitdir to find the
location of the worktree's gitfile (/path/to/worktree/.git), the path
recorded in `gitdir` is the old location of the worktree's gitfile, thus
it is unable to repair the gitfile since it doesn't know where it is.

Fix these shortcomings by teaching `repair` to attempt to infer the new
location of the <repo>/worktrees/<id>/gitdir file when the location
recorded in the worktree's gitfile has become stale but the file is
otherwise well-formed. The inference is intentionally simple-minded.
For each worktree path specified as an argument, `git worktree repair`
manually reads the ".git" gitfile at that location and, if it is
well-formed, extracts the <id>. It then searches for a corresponding
<id> in <repo>/worktrees/ and, if found, concludes that there is a
reasonable match and updates <repo>/worktrees/<id>/gitdir to point at
the specified worktree path. In order for <repo> to be known, `git
worktree repair` must be run in the main worktree or bare repository.

`git worktree repair` first attempts to repair each incoming
/path/to/worktree/.git gitfile to point at the repository, and then
attempts to repair outgoing <repo>/worktrees/<id>/gitdir files to point
at the worktrees. This sequence was chosen arbitrarily when originally
implemented since the order of fixes is immaterial as long as one side
of the two-way link between the repository and a worktree is sound.
However, for this new repair technique to work, the order must be
reversed. This is because the new inference mechanism, when it is
successful, allows the outgoing <repo>/worktrees/<id>/gitdir file to be
repaired, thus fixing one side of the two-way link. Once that side is
fixed, the other side can be fixed by the existing repair mechanism,
hence the order of repairs is now significant.

Two safeguards are employed to avoid hijacking a worktree from a
different repository if the user accidentally specifies a foreign
worktree as an argument. The first, as described above, is that it
requires an <id> match between the repository and the worktree. That
itself is not foolproof for preventing hijack, so the second safeguard
is that the inference will only kick in if the worktree's
/path/to/worktree/.git gitfile does not point at a repository.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-12-21 13:44:28 -08:00

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git-worktree(1)
===============
NAME
----
git-worktree - Manage multiple working trees
SYNOPSIS
--------
[verse]
'git worktree add' [-f] [--detach] [--checkout] [--lock] [-b <new-branch>] <path> [<commit-ish>]
'git worktree list' [--porcelain]
'git worktree lock' [--reason <string>] <worktree>
'git worktree move' <worktree> <new-path>
'git worktree prune' [-n] [-v] [--expire <expire>]
'git worktree remove' [-f] <worktree>
'git worktree repair' [<path>...]
'git worktree unlock' <worktree>
DESCRIPTION
-----------
Manage multiple working trees attached to the same repository.
A git repository can support multiple working trees, allowing you to check
out more than one branch at a time. With `git worktree add` a new working
tree is associated with the repository. This new working tree is called a
"linked working tree" as opposed to the "main working tree" prepared by
linkgit:git-init[1] or linkgit:git-clone[1].
A repository has one main working tree (if it's not a
bare repository) and zero or more linked working trees. When you are done
with a linked working tree, remove it with `git worktree remove`.
In its simplest form, `git worktree add <path>` automatically creates a
new branch whose name is the final component of `<path>`, which is
convenient if you plan to work on a new topic. For instance, `git
worktree add ../hotfix` creates new branch `hotfix` and checks it out at
path `../hotfix`. To instead work on an existing branch in a new working
tree, use `git worktree add <path> <branch>`. On the other hand, if you
just plan to make some experimental changes or do testing without
disturbing existing development, it is often convenient to create a
'throwaway' working tree not associated with any branch. For instance,
`git worktree add -d <path>` creates a new working tree with a detached
`HEAD` at the same commit as the current branch.
If a working tree is deleted without using `git worktree remove`, then
its associated administrative files, which reside in the repository
(see "DETAILS" below), will eventually be removed automatically (see
`gc.worktreePruneExpire` in linkgit:git-config[1]), or you can run
`git worktree prune` in the main or any linked working tree to
clean up any stale administrative files.
If a linked working tree is stored on a portable device or network share
which is not always mounted, you can prevent its administrative files from
being pruned by issuing the `git worktree lock` command, optionally
specifying `--reason` to explain why the working tree is locked.
COMMANDS
--------
add <path> [<commit-ish>]::
Create `<path>` and checkout `<commit-ish>` into it. The new working directory
is linked to the current repository, sharing everything except working
directory specific files such as `HEAD`, `index`, etc. As a convenience,
`<commit-ish>` may be a bare "`-`", which is synonymous with `@{-1}`.
+
If `<commit-ish>` is a branch name (call it `<branch>`) and is not found,
and neither `-b` nor `-B` nor `--detach` are used, but there does
exist a tracking branch in exactly one remote (call it `<remote>`)
with a matching name, treat as equivalent to:
+
------------
$ git worktree add --track -b <branch> <path> <remote>/<branch>
------------
+
If the branch exists in multiple remotes and one of them is named by
the `checkout.defaultRemote` configuration variable, we'll use that
one for the purposes of disambiguation, even if the `<branch>` isn't
unique across all remotes. Set it to
e.g. `checkout.defaultRemote=origin` to always checkout remote
branches from there if `<branch>` is ambiguous but exists on the
`origin` remote. See also `checkout.defaultRemote` in
linkgit:git-config[1].
+
If `<commit-ish>` is omitted and neither `-b` nor `-B` nor `--detach` used,
then, as a convenience, the new working tree is associated with a branch
(call it `<branch>`) named after `$(basename <path>)`. If `<branch>`
doesn't exist, a new branch based on `HEAD` is automatically created as
if `-b <branch>` was given. If `<branch>` does exist, it will be
checked out in the new working tree, if it's not checked out anywhere
else, otherwise the command will refuse to create the working tree (unless
`--force` is used).
list::
List details of each working tree. The main working tree is listed first,
followed by each of the linked working trees. The output details include
whether the working tree is bare, the revision currently checked out, the
branch currently checked out (or "detached HEAD" if none), and "locked" if
the worktree is locked.
lock::
If a working tree is on a portable device or network share which
is not always mounted, lock it to prevent its administrative
files from being pruned automatically. This also prevents it from
being moved or deleted. Optionally, specify a reason for the lock
with `--reason`.
move::
Move a working tree to a new location. Note that the main working tree
or linked working trees containing submodules cannot be moved with this
command. (The `git worktree repair` command, however, can reestablish
the connection with linked working trees if you move the main working
tree manually.)
prune::
Prune working tree information in `$GIT_DIR/worktrees`.
remove::
Remove a working tree. Only clean working trees (no untracked files
and no modification in tracked files) can be removed. Unclean working
trees or ones with submodules can be removed with `--force`. The main
working tree cannot be removed.
repair [<path>...]::
Repair working tree administrative files, if possible, if they have
become corrupted or outdated due to external factors.
+
For instance, if the main working tree (or bare repository) is moved,
linked working trees will be unable to locate it. Running `repair` in
the main working tree will reestablish the connection from linked
working trees back to the main working tree.
+
Similarly, if a linked working tree is moved without using `git worktree
move`, the main working tree (or bare repository) will be unable to
locate it. Running `repair` within the recently-moved working tree will
reestablish the connection. If multiple linked working trees are moved,
running `repair` from any working tree with each tree's new `<path>` as
an argument, will reestablish the connection to all the specified paths.
+
If both the main working tree and linked working trees have been moved
manually, then running `repair` in the main working tree and specifying the
new `<path>` of each linked working tree will reestablish all connections
in both directions.
unlock::
Unlock a working tree, allowing it to be pruned, moved or deleted.
OPTIONS
-------
-f::
--force::
By default, `add` refuses to create a new working tree when
`<commit-ish>` is a branch name and is already checked out by
another working tree, or if `<path>` is already assigned to some
working tree but is missing (for instance, if `<path>` was deleted
manually). This option overrides these safeguards. To add a missing but
locked working tree path, specify `--force` twice.
+
`move` refuses to move a locked working tree unless `--force` is specified
twice. If the destination is already assigned to some other working tree but is
missing (for instance, if `<new-path>` was deleted manually), then `--force`
allows the move to proceed; use `--force` twice if the destination is locked.
+
`remove` refuses to remove an unclean working tree unless `--force` is used.
To remove a locked working tree, specify `--force` twice.
-b <new-branch>::
-B <new-branch>::
With `add`, create a new branch named `<new-branch>` starting at
`<commit-ish>`, and check out `<new-branch>` into the new working tree.
If `<commit-ish>` is omitted, it defaults to `HEAD`.
By default, `-b` refuses to create a new branch if it already
exists. `-B` overrides this safeguard, resetting `<new-branch>` to
`<commit-ish>`.
-d::
--detach::
With `add`, detach `HEAD` in the new working tree. See "DETACHED HEAD"
in linkgit:git-checkout[1].
--[no-]checkout::
By default, `add` checks out `<commit-ish>`, however, `--no-checkout` can
be used to suppress checkout in order to make customizations,
such as configuring sparse-checkout. See "Sparse checkout"
in linkgit:git-read-tree[1].
--[no-]guess-remote::
With `worktree add <path>`, without `<commit-ish>`, instead
of creating a new branch from `HEAD`, if there exists a tracking
branch in exactly one remote matching the basename of `<path>`,
base the new branch on the remote-tracking branch, and mark
the remote-tracking branch as "upstream" from the new branch.
+
This can also be set up as the default behaviour by using the
`worktree.guessRemote` config option.
--[no-]track::
When creating a new branch, if `<commit-ish>` is a branch,
mark it as "upstream" from the new branch. This is the
default if `<commit-ish>` is a remote-tracking branch. See
`--track` in linkgit:git-branch[1] for details.
--lock::
Keep the working tree locked after creation. This is the
equivalent of `git worktree lock` after `git worktree add`,
but without a race condition.
-n::
--dry-run::
With `prune`, do not remove anything; just report what it would
remove.
--porcelain::
With `list`, output in an easy-to-parse format for scripts.
This format will remain stable across Git versions and regardless of user
configuration. See below for details.
-q::
--quiet::
With `add`, suppress feedback messages.
-v::
--verbose::
With `prune`, report all removals.
--expire <time>::
With `prune`, only expire unused working trees older than `<time>`.
--reason <string>::
With `lock`, an explanation why the working tree is locked.
<worktree>::
Working trees can be identified by path, either relative or
absolute.
+
If the last path components in the working tree's path is unique among
working trees, it can be used to identify a working tree. For example if
you only have two working trees, at `/abc/def/ghi` and `/abc/def/ggg`,
then `ghi` or `def/ghi` is enough to point to the former working tree.
REFS
----
In multiple working trees, some refs may be shared between all working
trees and some refs are local. One example is `HEAD` which is different for each
working tree. This section is about the sharing rules and how to access
refs of one working tree from another.
In general, all pseudo refs are per working tree and all refs starting
with `refs/` are shared. Pseudo refs are ones like `HEAD` which are
directly under `$GIT_DIR` instead of inside `$GIT_DIR/refs`. There are
exceptions, however: refs inside `refs/bisect` and `refs/worktree` are not
shared.
Refs that are per working tree can still be accessed from another
working tree via two special paths, `main-worktree` and `worktrees`. The
former gives access to per-working tree refs of the main working tree,
while the latter to all linked working trees.
For example, `main-worktree/HEAD` or `main-worktree/refs/bisect/good`
resolve to the same value as the main working tree's `HEAD` and
`refs/bisect/good` respectively. Similarly, `worktrees/foo/HEAD` or
`worktrees/bar/refs/bisect/bad` are the same as
`$GIT_COMMON_DIR/worktrees/foo/HEAD` and
`$GIT_COMMON_DIR/worktrees/bar/refs/bisect/bad`.
To access refs, it's best not to look inside `$GIT_DIR` directly. Instead
use commands such as linkgit:git-rev-parse[1] or linkgit:git-update-ref[1]
which will handle refs correctly.
CONFIGURATION FILE
------------------
By default, the repository `config` file is shared across all working
trees. If the config variables `core.bare` or `core.worktree` are
already present in the config file, they will be applied to the main
working trees only.
In order to have configuration specific to working trees, you can turn
on the `worktreeConfig` extension, e.g.:
------------
$ git config extensions.worktreeConfig true
------------
In this mode, specific configuration stays in the path pointed by `git
rev-parse --git-path config.worktree`. You can add or update
configuration in this file with `git config --worktree`. Older Git
versions will refuse to access repositories with this extension.
Note that in this file, the exception for `core.bare` and `core.worktree`
is gone. If they exist in `$GIT_DIR/config`, you must move
them to the `config.worktree` of the main working tree. You may also
take this opportunity to review and move other configuration that you
do not want to share to all working trees:
- `core.worktree` and `core.bare` should never be shared
- `core.sparseCheckout` is recommended per working tree, unless you
are sure you always use sparse checkout for all working trees.
DETAILS
-------
Each linked working tree has a private sub-directory in the repository's
`$GIT_DIR/worktrees` directory. The private sub-directory's name is usually
the base name of the linked working tree's path, possibly appended with a
number to make it unique. For example, when `$GIT_DIR=/path/main/.git` the
command `git worktree add /path/other/test-next next` creates the linked
working tree in `/path/other/test-next` and also creates a
`$GIT_DIR/worktrees/test-next` directory (or `$GIT_DIR/worktrees/test-next1`
if `test-next` is already taken).
Within a linked working tree, `$GIT_DIR` is set to point to this private
directory (e.g. `/path/main/.git/worktrees/test-next` in the example) and
`$GIT_COMMON_DIR` is set to point back to the main working tree's `$GIT_DIR`
(e.g. `/path/main/.git`). These settings are made in a `.git` file located at
the top directory of the linked working tree.
Path resolution via `git rev-parse --git-path` uses either
`$GIT_DIR` or `$GIT_COMMON_DIR` depending on the path. For example, in the
linked working tree `git rev-parse --git-path HEAD` returns
`/path/main/.git/worktrees/test-next/HEAD` (not
`/path/other/test-next/.git/HEAD` or `/path/main/.git/HEAD`) while `git
rev-parse --git-path refs/heads/master` uses
`$GIT_COMMON_DIR` and returns `/path/main/.git/refs/heads/master`,
since refs are shared across all working trees, except `refs/bisect` and
`refs/worktree`.
See linkgit:gitrepository-layout[5] for more information. The rule of
thumb is do not make any assumption about whether a path belongs to
`$GIT_DIR` or `$GIT_COMMON_DIR` when you need to directly access something
inside `$GIT_DIR`. Use `git rev-parse --git-path` to get the final path.
If you manually move a linked working tree, you need to update the `gitdir` file
in the entry's directory. For example, if a linked working tree is moved
to `/newpath/test-next` and its `.git` file points to
`/path/main/.git/worktrees/test-next`, then update
`/path/main/.git/worktrees/test-next/gitdir` to reference `/newpath/test-next`
instead. Better yet, run `git worktree repair` to reestablish the connection
automatically.
To prevent a `$GIT_DIR/worktrees` entry from being pruned (which
can be useful in some situations, such as when the
entry's working tree is stored on a portable device), use the
`git worktree lock` command, which adds a file named
`locked` to the entry's directory. The file contains the reason in
plain text. For example, if a linked working tree's `.git` file points
to `/path/main/.git/worktrees/test-next` then a file named
`/path/main/.git/worktrees/test-next/locked` will prevent the
`test-next` entry from being pruned. See
linkgit:gitrepository-layout[5] for details.
When `extensions.worktreeConfig` is enabled, the config file
`.git/worktrees/<id>/config.worktree` is read after `.git/config` is.
LIST OUTPUT FORMAT
------------------
The `worktree list` command has two output formats. The default format shows the
details on a single line with columns. For example:
------------
$ git worktree list
/path/to/bare-source (bare)
/path/to/linked-worktree abcd1234 [master]
/path/to/other-linked-worktree 1234abc (detached HEAD)
------------
Porcelain Format
~~~~~~~~~~~~~~~~
The porcelain format has a line per attribute. Attributes are listed with a
label and value separated by a single space. Boolean attributes (like `bare`
and `detached`) are listed as a label only, and are present only
if the value is true. The first attribute of a working tree is always
`worktree`, an empty line indicates the end of the record. For example:
------------
$ git worktree list --porcelain
worktree /path/to/bare-source
bare
worktree /path/to/linked-worktree
HEAD abcd1234abcd1234abcd1234abcd1234abcd1234
branch refs/heads/master
worktree /path/to/other-linked-worktree
HEAD 1234abc1234abc1234abc1234abc1234abc1234a
detached
------------
EXAMPLES
--------
You are in the middle of a refactoring session and your boss comes in and
demands that you fix something immediately. You might typically use
linkgit:git-stash[1] to store your changes away temporarily, however, your
working tree is in such a state of disarray (with new, moved, and removed
files, and other bits and pieces strewn around) that you don't want to risk
disturbing any of it. Instead, you create a temporary linked working tree to
make the emergency fix, remove it when done, and then resume your earlier
refactoring session.
------------
$ git worktree add -b emergency-fix ../temp master
$ pushd ../temp
# ... hack hack hack ...
$ git commit -a -m 'emergency fix for boss'
$ popd
$ git worktree remove ../temp
------------
BUGS
----
Multiple checkout in general is still experimental, and the support
for submodules is incomplete. It is NOT recommended to make multiple
checkouts of a superproject.
GIT
---
Part of the linkgit:git[1] suite
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