Merge branch 'nd/switch-and-restore'

Two new commands "git switch" and "git restore" are introduced to
split "checking out a branch to work on advancing its history" and
"checking out paths out of the index and/or a tree-ish to work on
advancing the current history" out of the single "git checkout"
command.

* nd/switch-and-restore: (46 commits)
  completion: disable dwim on "git switch -d"
  switch: allow to switch in the middle of bisect
  t2027: use test_must_be_empty
  Declare both git-switch and git-restore experimental
  help: move git-diff and git-reset to different groups
  doc: promote "git restore"
  user-manual.txt: prefer 'merge --abort' over 'reset --hard'
  completion: support restore
  t: add tests for restore
  restore: support --patch
  restore: replace --force with --ignore-unmerged
  restore: default to --source=HEAD when only --staged is specified
  restore: reject invalid combinations with --staged
  restore: add --worktree and --staged
  checkout: factor out worktree checkout code
  restore: disable overlay mode by default
  restore: make pathspec mandatory
  restore: take tree-ish from --source option instead
  checkout: split part of it to new command 'restore'
  doc: promote "git switch"
  ...

1 files changed, 122 insertions, 100 deletions

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 964f912d29..cf3cac0a2b 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -23,31 +23,22 @@ or the specified tree.  If no paths are given, 'git checkout' will
 also update `HEAD` to set the specified branch as the current
 branch.
 
-'git checkout' <branch>::
-	To prepare for working on <branch>, switch to it by updating
+'git checkout' [<branch>]::
+	To prepare for working on `<branch>`, switch to it by updating
 	the index and the files in the working tree, and by pointing
-	HEAD at the branch. Local modifications to the files in the
+	`HEAD` at the branch. Local modifications to the files in the
 	working tree are kept, so that they can be committed to the
-	<branch>.
+	`<branch>`.
 +
-If <branch> is not found but there does exist a tracking branch in
-exactly one remote (call it <remote>) with a matching name, treat as
-equivalent to
+If `<branch>` is not found but there does exist a tracking branch in
+exactly one remote (call it `<remote>`) with a matching name and
+`--no-guess` is not specified, treat as equivalent to
 +
 ------------
 $ git checkout -b <branch> --track <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].
-+
-You could omit <branch>, in which case the command degenerates to
+You could omit `<branch>`, in which case the command degenerates to
 "check out the current branch", which is a glorified no-op with
 rather expensive side-effects to show only the tracking information,
 if exists, for the current branch.
@@ -61,7 +52,7 @@ if exists, for the current branch.
 	`--track` without `-b` implies branch creation; see the
 	description of `--track` below.
 +
-If `-B` is given, <new_branch> is created if it doesn't exist; otherwise, it
+If `-B` is given, `<new_branch>` is created if it doesn't exist; otherwise, it
 is reset. This is the transactional equivalent of
 +
 ------------
@@ -75,25 +66,25 @@ successful.
 'git checkout' --detach [<branch>]::
 'git checkout' [--detach] <commit>::
 
-	Prepare to work on top of <commit>, by detaching HEAD at it
+	Prepare to work on top of `<commit>`, by detaching `HEAD` at it
 	(see "DETACHED HEAD" section), and updating the index and the
 	files in the working tree.  Local modifications to the files
 	in the working tree are kept, so that the resulting working
 	tree will be the state recorded in the commit plus the local
 	modifications.
 +
-When the <commit> argument is a branch name, the `--detach` option can
-be used to detach HEAD at the tip of the branch (`git checkout
-<branch>` would check out that branch without detaching HEAD).
+When the `<commit>` argument is a branch name, the `--detach` option can
+be used to detach `HEAD` at the tip of the branch (`git checkout
+<branch>` would check out that branch without detaching `HEAD`).
 +
-Omitting <branch> detaches HEAD at the tip of the current branch.
+Omitting `<branch>` detaches `HEAD` at the tip of the current branch.
 
 'git checkout' [<tree-ish>] [--] <pathspec>...::
 
 	Overwrite paths in the working tree by replacing with the
-	contents in the index or in the <tree-ish> (most often a
-	commit).  When a <tree-ish> is given, the paths that
-	match the <pathspec> are updated both in the index and in
+	contents in the index or in the `<tree-ish>` (most often a
+	commit).  When a `<tree-ish>` is given, the paths that
+	match the `<pathspec>` are updated both in the index and in
 	the working tree.
 +
 The index may contain unmerged entries because of a previous failed merge.
@@ -118,7 +109,8 @@ OPTIONS
 --quiet::
 	Quiet, suppress feedback messages.
 
---[no-]progress::
+--progress::
+--no-progress::
 	Progress status is reported on the standard error stream
 	by default when it is attached to a terminal, unless `--quiet`
 	is specified. This flag enables progress reporting even if not
@@ -127,7 +119,7 @@ OPTIONS
 -f::
 --force::
 	When switching branches, proceed even if the index or the
-	working tree differs from HEAD.  This is used to throw away
+	working tree differs from `HEAD`.  This is used to throw away
 	local changes.
 +
 When checking out paths from the index, do not fail upon unmerged
@@ -154,12 +146,12 @@ on your side branch as `theirs` (i.e. "one contributor's work on top
 of it").
 
 -b <new_branch>::
-	Create a new branch named <new_branch> and start it at
-	<start_point>; see linkgit:git-branch[1] for details.
+	Create a new branch named `<new_branch>` and start it at
+	`<start_point>`; see linkgit:git-branch[1] for details.
 
 -B <new_branch>::
-	Creates the branch <new_branch> and start it at <start_point>;
-	if it already exists, then reset it to <start_point>. This is
+	Creates the branch `<new_branch>` and start it at `<start_point>`;
+	if it already exists, then reset it to `<start_point>`. This is
 	equivalent to running "git branch" with "-f"; see
 	linkgit:git-branch[1] for details.
 
@@ -172,15 +164,36 @@ If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
 the initial part up to the "*".
-This would tell us to use "hack" as the local branch when branching
-off of "origin/hack" (or "remotes/origin/hack", or even
-"refs/remotes/origin/hack").  If the given name has no slash, or the above
+This would tell us to use `hack` as the local branch when branching
+off of `origin/hack` (or `remotes/origin/hack`, or even
+`refs/remotes/origin/hack`).  If the given name has no slash, or the above
 guessing results in an empty name, the guessing is aborted.  You can
 explicitly give a name with `-b` in such a case.
 
 --no-track::
 	Do not set up "upstream" configuration, even if the
-	branch.autoSetupMerge configuration variable is true.
+	`branch.autoSetupMerge` configuration variable is true.
+
+--guess::
+--no-guess::
+	If `<branch>` is not found but there does exist a tracking
+	branch in exactly one remote (call it `<remote>`) with a
+	matching name, treat as equivalent to
++
+------------
+$ git checkout -b <branch> --track <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].
++
+Use `--no-guess` to disable this.
 
 -l::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
@@ -189,21 +202,21 @@ explicitly give a name with `-b` in such a case.
 --detach::
 	Rather than checking out a branch to work on it, check out a
 	commit for inspection and discardable experiments.
-	This is the default behavior of "git checkout <commit>" when
-	<commit> is not a branch name.  See the "DETACHED HEAD" section
+	This is the default behavior of `git checkout <commit>` when
+	`<commit>` is not a branch name.  See the "DETACHED HEAD" section
 	below for details.
 
 --orphan <new_branch>::
-	Create a new 'orphan' branch, named <new_branch>, started from
-	<start_point> and switch to it.  The first commit made on this
+	Create a new 'orphan' branch, named `<new_branch>`, started from
+	`<start_point>` and switch to it.  The first commit made on this
 	new branch will have no parents and it will be the root of a new
 	history totally disconnected from all the other branches and
 	commits.
 +
 The index and the working tree are adjusted as if you had previously run
-"git checkout <start_point>".  This allows you to start a new history
-that records a set of paths similar to <start_point> by easily running
-"git commit -a" to make the root commit.
+`git checkout <start_point>`.  This allows you to start a new history
+that records a set of paths similar to `<start_point>` by easily running
+`git commit -a` to make the root commit.
 +
 This can be useful when you want to publish the tree from a commit
 without exposing its full history. You might want to do this to publish
@@ -212,17 +225,17 @@ whose full history contains proprietary or otherwise encumbered bits of
 code.
 +
 If you want to start a disconnected history that records a set of paths
-that is totally different from the one of <start_point>, then you should
+that is totally different from the one of `<start_point>`, then you should
 clear the index and the working tree right after creating the orphan
-branch by running "git rm -rf ." from the top level of the working tree.
+branch by running `git rm -rf .` from the top level of the working tree.
 Afterwards you will be ready to prepare your new files, repopulating the
 working tree, by copying them from elsewhere, extracting a tarball, etc.
 
 --ignore-skip-worktree-bits::
 	In sparse checkout mode, `git checkout -- <paths>` would
-	update only entries matched by <paths> and sparse patterns
-	in $GIT_DIR/info/sparse-checkout. This option ignores
-	the sparse patterns and adds back any files in <paths>.
+	update only entries matched by `<paths>` and sparse patterns
+	in `$GIT_DIR/info/sparse-checkout`. This option ignores
+	the sparse patterns and adds back any files in `<paths>`.
 
 -m::
 --merge::
@@ -246,25 +259,25 @@ the conflicted merge in the specified paths.
 When switching branches with `--merge`, staged changes may be lost.
 
 --conflict=<style>::
-	The same as --merge option above, but changes the way the
+	The same as `--merge` option above, but changes the way the
 	conflicting hunks are presented, overriding the
-	merge.conflictStyle configuration variable.  Possible values are
+	`merge.conflictStyle` configuration variable.  Possible values are
 	"merge" (default) and "diff3" (in addition to what is shown by
 	"merge" style, shows the original contents).
 
 -p::
 --patch::
 	Interactively select hunks in the difference between the
-	<tree-ish> (or the index, if unspecified) and the working
+	`<tree-ish>` (or the index, if unspecified) and the working
 	tree.  The chosen hunks are then applied in reverse to the
-	working tree (and if a <tree-ish> was specified, the index).
+	working tree (and if a `<tree-ish>` was specified, the index).
 +
 This means that you can use `git checkout -p` to selectively discard
 edits from your current working tree. See the ``Interactive Mode''
 section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 +
 Note that this option uses the no overlay mode by default (see also
-`--[no-]overlay`), and currently doesn't support overlay mode.
+`--overlay`), and currently doesn't support overlay mode.
 
 --ignore-other-worktrees::
 	`git checkout` refuses when the wanted ref is already checked
@@ -272,38 +285,42 @@ Note that this option uses the no overlay mode by default (see also
 	out anyway. In other words, the ref can be held by more than one
 	worktree.
 
---[no-]recurse-submodules::
-	Using --recurse-submodules will update the content of all initialized
+--overwrite-ignore::
+--no-overwrite-ignore::
+	Silently overwrite ignored files when switching branches. This
+	is the default behavior. Use `--no-overwrite-ignore` to abort
+	the operation when the new branch contains ignored files.
+
+--recurse-submodules::
+--no-recurse-submodules::
+	Using `--recurse-submodules` will update the content of all initialized
 	submodules according to the commit recorded in the superproject. If
 	local modifications in a submodule would be overwritten the checkout
-	will fail unless `-f` is used. If nothing (or --no-recurse-submodules)
+	will fail unless `-f` is used. If nothing (or `--no-recurse-submodules`)
 	is used, the work trees of submodules will not be updated.
-	Just like linkgit:git-submodule[1], this will detach the
-	submodules HEAD.
-
---no-guess::
-	Do not attempt to create a branch if a remote tracking branch
-	of the same name exists.
+	Just like linkgit:git-submodule[1], this will detach `HEAD` of the
+	submodule.
 
---[no-]overlay::
+--overlay::
+--no-overlay::
 	In the default overlay mode, `git checkout` never
 	removes files from the index or the working tree.  When
 	specifying `--no-overlay`, files that appear in the index and
-	working tree, but not in <tree-ish> are removed, to make them
-	match <tree-ish> exactly.
+	working tree, but not in `<tree-ish>` are removed, to make them
+	match `<tree-ish>` exactly.
 
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
 	branch is checked out. Otherwise, if it refers to a valid
-	commit, your HEAD becomes "detached" and you are no longer on
+	commit, your `HEAD` becomes "detached" and you are no longer on
 	any branch (see below for details).
 +
-You can use the `"@{-N}"` syntax to refer to the N-th last
+You can use the `@{-N}` syntax to refer to the N-th last
 branch/commit checked out using "git checkout" operation. You may
-also specify `-` which is synonymous to `"@{-1}"`.
+also specify `-` which is synonymous to `@{-1}`.
 +
-As a special case, you may use `"A...B"` as a shortcut for the
+As a special case, you may use `A...B` as a shortcut for the
 merge base of `A` and `B` if there is exactly one merge base. You can
 leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
@@ -312,7 +329,7 @@ leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 <start_point>::
 	The name of a commit at which to start the new branch; see
-	linkgit:git-branch[1] for details. Defaults to HEAD.
+	linkgit:git-branch[1] for details. Defaults to `HEAD`.
 +
 As a special case, you may use `"A...B"` as a shortcut for the
 merge base of `A` and `B` if there is exactly one merge base. You can
@@ -326,9 +343,9 @@ leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.
 
 DETACHED HEAD
 -------------
-HEAD normally refers to a named branch (e.g. 'master'). Meanwhile, each
+`HEAD` normally refers to a named branch (e.g. `master`). Meanwhile, each
 branch refers to a specific commit. Let's look at a repo with three
-commits, one of them tagged, and with branch 'master' checked out:
+commits, one of them tagged, and with branch `master` checked out:
 
 ------------
            HEAD (refers to branch 'master')
@@ -341,10 +358,10 @@ a---b---c  branch 'master' (refers to commit 'c')
 ------------
 
 When a commit is created in this state, the branch is updated to refer to
-the new commit. Specifically, 'git commit' creates a new commit 'd', whose
-parent is commit 'c', and then updates branch 'master' to refer to new
-commit 'd'. HEAD still refers to branch 'master' and so indirectly now refers
-to commit 'd':
+the new commit. Specifically, 'git commit' creates a new commit `d`, whose
+parent is commit `c`, and then updates branch `master` to refer to new
+commit `d`. `HEAD` still refers to branch `master` and so indirectly now refers
+to commit `d`:
 
 ------------
 $ edit; git add; git commit
@@ -361,7 +378,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 It is sometimes useful to be able to checkout a commit that is not at
 the tip of any named branch, or even to create a new commit that is not
 referenced by a named branch. Let's look at what happens when we
-checkout commit 'b' (here we show two ways this may be done):
+checkout commit `b` (here we show two ways this may be done):
 
 ------------
 $ git checkout v2.0  # or
@@ -376,9 +393,9 @@ a---b---c---d  branch 'master' (refers to commit 'd')
   tag 'v2.0' (refers to commit 'b')
 ------------
 
-Notice that regardless of which checkout command we use, HEAD now refers
-directly to commit 'b'. This is known as being in detached HEAD state.
-It means simply that HEAD refers to a specific commit, as opposed to
+Notice that regardless of which checkout command we use, `HEAD` now refers
+directly to commit `b`. This is known as being in detached `HEAD` state.
+It means simply that `HEAD` refers to a specific commit, as opposed to
 referring to a named branch. Let's see what happens when we create a commit:
 
 ------------
@@ -395,7 +412,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
   tag 'v2.0' (refers to commit 'b')
 ------------
 
-There is now a new commit 'e', but it is referenced only by HEAD. We can
+There is now a new commit `e`, but it is referenced only by `HEAD`. We can
 of course add yet another commit in this state:
 
 ------------
@@ -413,7 +430,7 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 ------------
 
 In fact, we can perform all the normal Git operations. But, let's look
-at what happens when we then checkout master:
+at what happens when we then checkout `master`:
 
 ------------
 $ git checkout master
@@ -428,9 +445,9 @@ a---b---c---d  branch 'master' (refers to commit 'd')
 ------------
 
 It is important to realize that at this point nothing refers to commit
-'f'. Eventually commit 'f' (and by extension commit 'e') will be deleted
+`f`. Eventually commit `f` (and by extension commit `e`) will be deleted
 by the routine Git garbage collection process, unless we create a reference
-before that happens. If we have not yet moved away from commit 'f',
+before that happens. If we have not yet moved away from commit `f`,
 any of these will create a reference to it:
 
 ------------
@@ -439,19 +456,19 @@ $ git branch foo        <2>
 $ git tag foo           <3>
 ------------
 
-<1> creates a new branch 'foo', which refers to commit 'f', and then
-    updates HEAD to refer to branch 'foo'. In other words, we'll no longer
-    be in detached HEAD state after this command.
+<1> creates a new branch `foo`, which refers to commit `f`, and then
+    updates `HEAD` to refer to branch `foo`. In other words, we'll no longer
+    be in detached `HEAD` state after this command.
 
-<2> similarly creates a new branch 'foo', which refers to commit 'f',
-    but leaves HEAD detached.
+<2> similarly creates a new branch `foo`, which refers to commit `f`,
+    but leaves `HEAD` detached.
 
-<3> creates a new tag 'foo', which refers to commit 'f',
-    leaving HEAD detached.
+<3> creates a new tag `foo`, which refers to commit `f`,
+    leaving `HEAD` detached.
 
-If we have moved away from commit 'f', then we must first recover its object
+If we have moved away from commit `f`, then we must first recover its object
 name (typically by using git reflog), and then we can create a reference to
-it. For example, to see the last two commits to which HEAD referred, we
+it. For example, to see the last two commits to which `HEAD` referred, we
 can use either of these commands:
 
 ------------
@@ -462,12 +479,12 @@ $ git log -g -2 HEAD
 ARGUMENT DISAMBIGUATION
 -----------------------
 
-When there is only one argument given and it is not `--` (e.g. "git
-checkout abc"), and when the argument is both a valid `<tree-ish>`
-(e.g. a branch "abc" exists) and a valid `<pathspec>` (e.g. a file
+When there is only one argument given and it is not `--` (e.g. `git
+checkout abc`), and when the argument is both a valid `<tree-ish>`
+(e.g. a branch `abc` exists) and a valid `<pathspec>` (e.g. a file
 or a directory whose name is "abc" exists), Git would usually ask
 you to disambiguate.  Because checking out a branch is so common an
-operation, however, "git checkout abc" takes "abc" as a `<tree-ish>`
+operation, however, `git checkout abc` takes "abc" as a `<tree-ish>`
 in such a situation.  Use `git checkout -- <pathspec>` if you want
 to checkout these paths out of the index.
 
@@ -475,7 +492,7 @@ EXAMPLES
 --------
 
 . The following sequence checks out the `master` branch, reverts
-  the `Makefile` to two revisions back, deletes hello.c by
+  the `Makefile` to two revisions back, deletes `hello.c` by
   mistake, and gets it back from the index.
 +
 ------------
@@ -487,7 +504,7 @@ $ git checkout hello.c            <3>
 +
 <1> switch branch
 <2> take a file out of another commit
-<3> restore hello.c from the index
+<3> restore `hello.c` from the index
 +
 If you want to check out _all_ C source files out of the index,
 you can say
@@ -516,7 +533,7 @@ $ git checkout -- hello.c
 $ git checkout mytopic
 ------------
 +
-However, your "wrong" branch and correct "mytopic" branch may
+However, your "wrong" branch and correct `mytopic` branch may
 differ in files that you have modified locally, in which case
 the above checkout would fail like this:
 +
@@ -557,6 +574,11 @@ $ edit frotz
 $ git add frotz
 ------------
 
+SEE ALSO
+--------
+linkgit:git-switch[1],
+linkgit:git-restore[1]
+
 GIT
 ---
 Part of the linkgit:git[1] suite