merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

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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 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 "git
+init" or "git clone".  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`.
+
+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. `-` may also be
+specified as `<commit-ish>`; it 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 worktree 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 worktree, if it's not checked out anywhere
+else, otherwise the command will refuse to create the worktree (unless
+`--force` is used).
+
+list::
+
+List details of each worktree.  The main worktree is listed first, followed by
+each of the linked worktrees.  The output details include if the worktree is
+bare, the revision currently checked out, and the branch currently checked out
+(or 'detached HEAD' if none).
+
+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.
+
+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.
+
+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.
++
+`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>`.
+
+--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 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 worktrees. 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, some refs are local. One example is HEAD is different for all
+working trees. 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 is one
+exception to this: refs inside refs/bisect and refs/worktree is 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-worktree 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 "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 you have them in $GIT_DIR/config before, you must move
+them to the `config.worktree` of the main working tree. You may also
+take this opportunity to review and move other configuration that you
+do not want to share to all working trees:
+
+ - `core.worktree` and `core.bare` should never be shared
+
+ - `core.sparseCheckout` is recommended per working tree, unless you
+   are sure you always use sparse checkout for all working trees.
+
+DETAILS
+-------
+Each linked working tree has a private sub-directory in the repository's
+$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.
+
+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 only present if and only
+if the value is true.  The first attribute of a worktree 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