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

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+git-reset(1)
+============
+
+NAME
+----
+git-reset - Reset current HEAD to the specified state
+
+SYNOPSIS
+--------
+[verse]
+'git reset' [-q] [<tree-ish>] [--] <paths>...
+'git reset' (--patch | -p) [<tree-ish>] [--] [<paths>...]
+'git reset' [--soft | --mixed [-N] | --hard | --merge | --keep] [-q] [<commit>]
+
+DESCRIPTION
+-----------
+In the first and second form, copy entries from `<tree-ish>` to the index.
+In the third form, set the current branch head (`HEAD`) to `<commit>`,
+optionally modifying index and working tree to match.
+The `<tree-ish>`/`<commit>` defaults to `HEAD` in all forms.
+
+'git reset' [-q] [<tree-ish>] [--] <paths>...::
+	This form resets the index entries for all `<paths>` to their
+	state at `<tree-ish>`.  (It does not affect the working tree or
+	the current branch.)
++
+This means that `git reset <paths>` is the opposite of `git add
+<paths>`. This command is equivalent to
+`git restore [--source=<tree-ish>] --staged <paths>...`.
++
+After running `git reset <paths>` to update the index entry, you can
+use linkgit:git-restore[1] to check the contents out of the index to
+the working tree. Alternatively, using linkgit:git-restore[1]
+and specifying a commit with `--source`, you
+can copy the contents of a path out of a commit to the index and to the
+working tree in one go.
+
+'git reset' (--patch | -p) [<tree-ish>] [--] [<paths>...]::
+	Interactively select hunks in the difference between the index
+	and `<tree-ish>` (defaults to `HEAD`).  The chosen hunks are applied
+	in reverse to the index.
++
+This means that `git reset -p` is the opposite of `git add -p`, i.e.
+you can use it to selectively reset hunks. See the ``Interactive Mode''
+section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
+
+'git reset' [<mode>] [<commit>]::
+	This form resets the current branch head to `<commit>` and
+	possibly updates the index (resetting it to the tree of `<commit>`) and
+	the working tree depending on `<mode>`. If `<mode>` is omitted,
+	defaults to `--mixed`. The `<mode>` must be one of the following:
++
+--
+--soft::
+	Does not touch the index file or the working tree at all (but
+	resets the head to `<commit>`, just like all modes do). This leaves
+	all your changed files "Changes to be committed", as `git status`
+	would put it.
+
+--mixed::
+	Resets the index but not the working tree (i.e., the changed files
+	are preserved but not marked for commit) and reports what has not
+	been updated. This is the default action.
++
+If `-N` is specified, removed paths are marked as intent-to-add (see
+linkgit:git-add[1]).
+
+--hard::
+	Resets the index and working tree. Any changes to tracked files in the
+	working tree since `<commit>` are discarded.
+
+--merge::
+	Resets the index and updates the files in the working tree that are
+	different between `<commit>` and `HEAD`, but keeps those which are
+	different between the index and working tree (i.e. which have changes
+	which have not been added).
+	If a file that is different between `<commit>` and the index has
+	unstaged changes, reset is aborted.
++
+In other words, `--merge` does something like a `git read-tree -u -m <commit>`,
+but carries forward unmerged index entries.
+
+--keep::
+	Resets index entries and updates files in the working tree that are
+	different between `<commit>` and `HEAD`.
+	If a file that is different between `<commit>` and `HEAD` has local
+	changes, reset is aborted.
+--
+
+See "Reset, restore and revert" in linkgit:git[1] for the differences
+between the three commands.
+
+
+OPTIONS
+-------
+
+-q::
+--quiet::
+--no-quiet::
+	Be quiet, only report errors. The default behavior is set by the
+	`reset.quiet` config option. `--quiet` and `--no-quiet` will
+	override the default behavior.
+
+
+EXAMPLES
+--------
+
+Undo add::
++
+------------
+$ edit                                     <1>
+$ git add frotz.c filfre.c
+$ mailx                                    <2>
+$ git reset                                <3>
+$ git pull git://info.example.com/ nitfol  <4>
+------------
++
+<1> You are happily working on something, and find the changes
+    in these files are in good order.  You do not want to see them
+    when you run `git diff`, because you plan to work on other files
+    and changes with these files are distracting.
+<2> Somebody asks you to pull, and the changes sound worthy of merging.
+<3> However, you already dirtied the index (i.e. your index does
+    not match the `HEAD` commit).  But you know the pull you are going
+    to make does not affect `frotz.c` or `filfre.c`, so you revert the
+    index changes for these two files.  Your changes in working tree
+    remain there.
+<4> Then you can pull and merge, leaving `frotz.c` and `filfre.c`
+    changes still in the working tree.
+
+Undo a commit and redo::
++
+------------
+$ git commit ...
+$ git reset --soft HEAD^      <1>
+$ edit                        <2>
+$ git commit -a -c ORIG_HEAD  <3>
+------------
++
+<1> This is most often done when you remembered what you
+    just committed is incomplete, or you misspelled your commit
+    message, or both.  Leaves working tree as it was before "reset".
+<2> Make corrections to working tree files.
+<3> "reset" copies the old head to `.git/ORIG_HEAD`; redo the
+    commit by starting with its log message.  If you do not need to
+    edit the message further, you can give `-C` option instead.
++
+See also the `--amend` option to linkgit:git-commit[1].
+
+Undo a commit, making it a topic branch::
++
+------------
+$ git branch topic/wip          <1>
+$ git reset --hard HEAD~3       <2>
+$ git switch topic/wip          <3>
+------------
++
+<1> You have made some commits, but realize they were premature
+    to be in the `master` branch.  You want to continue polishing
+    them in a topic branch, so create `topic/wip` branch off of the
+    current `HEAD`.
+<2> Rewind the master branch to get rid of those three commits.
+<3> Switch to `topic/wip` branch and keep working.
+
+Undo commits permanently::
++
+------------
+$ git commit ...
+$ git reset --hard HEAD~3   <1>
+------------
++
+<1> The last three commits (`HEAD`, `HEAD^`, and `HEAD~2`) were bad
+    and you do not want to ever see them again.  Do *not* do this if
+    you have already given these commits to somebody else.  (See the
+    "RECOVERING FROM UPSTREAM REBASE" section in linkgit:git-rebase[1]
+    for the implications of doing so.)
+
+Undo a merge or pull::
++
+------------
+$ git pull                         <1>
+Auto-merging nitfol
+CONFLICT (content): Merge conflict in nitfol
+Automatic merge failed; fix conflicts and then commit the result.
+$ git reset --hard                 <2>
+$ git pull . topic/branch          <3>
+Updating from 41223... to 13134...
+Fast-forward
+$ git reset --hard ORIG_HEAD       <4>
+------------
++
+<1> Try to update from the upstream resulted in a lot of
+    conflicts; you were not ready to spend a lot of time merging
+    right now, so you decide to do that later.
+<2> "pull" has not made merge commit, so `git reset --hard`
+    which is a synonym for `git reset --hard HEAD` clears the mess
+    from the index file and the working tree.
+<3> Merge a topic branch into the current branch, which resulted
+    in a fast-forward.
+<4> But you decided that the topic branch is not ready for public
+    consumption yet.  "pull" or "merge" always leaves the original
+    tip of the current branch in `ORIG_HEAD`, so resetting hard to it
+    brings your index file and the working tree back to that state,
+    and resets the tip of the branch to that commit.
+
+Undo a merge or pull inside a dirty working tree::
++
+------------
+$ git pull                         <1>
+Auto-merging nitfol
+Merge made by recursive.
+ nitfol                |   20 +++++----
+ ...
+$ git reset --merge ORIG_HEAD      <2>
+------------
++
+<1> Even if you may have local modifications in your
+    working tree, you can safely say `git pull` when you know
+    that the change in the other branch does not overlap with
+    them.
+<2> After inspecting the result of the merge, you may find
+    that the change in the other branch is unsatisfactory.  Running
+    `git reset --hard ORIG_HEAD` will let you go back to where you
+    were, but it will discard your local changes, which you do not
+    want.  `git reset --merge` keeps your local changes.
+
+
+Interrupted workflow::
++
+Suppose you are interrupted by an urgent fix request while you
+are in the middle of a large change.  The files in your
+working tree are not in any shape to be committed yet, but you
+need to get to the other branch for a quick bugfix.
++
+------------
+$ git switch feature  ;# you were working in "feature" branch and
+$ work work work      ;# got interrupted
+$ git commit -a -m "snapshot WIP"                 <1>
+$ git switch master
+$ fix fix fix
+$ git commit ;# commit with real log
+$ git switch feature
+$ git reset --soft HEAD^ ;# go back to WIP state  <2>
+$ git reset                                       <3>
+------------
++
+<1> This commit will get blown away so a throw-away log message is OK.
+<2> This removes the 'WIP' commit from the commit history, and sets
+    your working tree to the state just before you made that snapshot.
+<3> At this point the index file still has all the WIP changes you
+    committed as 'snapshot WIP'.  This updates the index to show your
+    WIP files as uncommitted.
++
+See also linkgit:git-stash[1].
+
+Reset a single file in the index::
++
+Suppose you have added a file to your index, but later decide you do not
+want to add it to your commit. You can remove the file from the index
+while keeping your changes with git reset.
++
+------------
+$ git reset -- frotz.c                      <1>
+$ git commit -m "Commit files in index"     <2>
+$ git add frotz.c                           <3>
+------------
++
+<1> This removes the file from the index while keeping it in the working
+    directory.
+<2> This commits all other changes in the index.
+<3> Adds the file to the index again.
+
+Keep changes in working tree while discarding some previous commits::
++
+Suppose you are working on something and you commit it, and then you
+continue working a bit more, but now you think that what you have in
+your working tree should be in another branch that has nothing to do
+with what you committed previously. You can start a new branch and
+reset it while keeping the changes in your working tree.
++
+------------
+$ git tag start
+$ git switch -c branch1
+$ edit
+$ git commit ...                            <1>
+$ edit
+$ git switch -c branch2                     <2>
+$ git reset --keep start                    <3>
+------------
++
+<1> This commits your first edits in `branch1`.
+<2> In the ideal world, you could have realized that the earlier
+    commit did not belong to the new topic when you created and switched
+    to `branch2` (i.e. `git switch -c branch2 start`), but nobody is
+    perfect.
+<3> But you can use `reset --keep` to remove the unwanted commit after
+    you switched to `branch2`.
+
+Split a commit apart into a sequence of commits::
++
+Suppose that you have created lots of logically separate changes and committed
+them together. Then, later you decide that it might be better to have each
+logical chunk associated with its own commit. You can use git reset to rewind
+history without changing the contents of your local files, and then successively
+use `git add -p` to interactively select which hunks to include into each commit,
+using `git commit -c` to pre-populate the commit message.
++
+------------
+$ git reset -N HEAD^                        <1>
+$ git add -p                                <2>
+$ git diff --cached                         <3>
+$ git commit -c HEAD@{1}                    <4>
+...                                         <5>
+$ git add ...                               <6>
+$ git diff --cached                         <7>
+$ git commit ...                            <8>
+------------
++
+<1> First, reset the history back one commit so that we remove the original
+    commit, but leave the working tree with all the changes. The -N ensures
+    that any new files added with `HEAD` are still marked so that `git add -p`
+    will find them.
+<2> Next, we interactively select diff hunks to add using the `git add -p`
+    facility. This will ask you about each diff hunk in sequence and you can
+    use simple commands such as "yes, include this", "No don't include this"
+    or even the very powerful "edit" facility.
+<3> Once satisfied with the hunks you want to include, you should verify what
+    has been prepared for the first commit by using `git diff --cached`. This
+    shows all the changes that have been moved into the index and are about
+    to be committed.
+<4> Next, commit the changes stored in the index. The `-c` option specifies to
+    pre-populate the commit message from the original message that you started
+    with in the first commit. This is helpful to avoid retyping it. The
+    `HEAD@{1}` is a special notation for the commit that `HEAD` used to be at
+    prior to the original reset commit (1 change ago).
+    See linkgit:git-reflog[1] for more details. You may also use any other
+    valid commit reference.
+<5> You can repeat steps 2-4 multiple times to break the original code into
+    any number of commits.
+<6> Now you've split out many of the changes into their own commits, and might
+    no longer use the patch mode of `git add`, in order to select all remaining
+    uncommitted changes.
+<7> Once again, check to verify that you've included what you want to. You may
+    also wish to verify that git diff doesn't show any remaining changes to be
+    committed later.
+<8> And finally create the final commit.
+
+
+DISCUSSION
+----------
+
+The tables below show what happens when running:
+
+----------
+git reset --option target
+----------
+
+to reset the `HEAD` to another commit (`target`) with the different
+reset options depending on the state of the files.
+
+In these tables, `A`, `B`, `C` and `D` are some different states of a
+file. For example, the first line of the first table means that if a
+file is in state `A` in the working tree, in state `B` in the index, in
+state `C` in `HEAD` and in state `D` in the target, then `git reset --soft
+target` will leave the file in the working tree in state `A` and in the
+index in state `B`.  It resets (i.e. moves) the `HEAD` (i.e. the tip of
+the current branch, if you are on one) to `target` (which has the file
+in state `D`).
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ A       B     C    D     --soft   A       B     D
+			  --mixed  A       D     D
+			  --hard   D       D     D
+			  --merge (disallowed)
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ A       B     C    C     --soft   A       B     C
+			  --mixed  A       C     C
+			  --hard   C       C     C
+			  --merge (disallowed)
+			  --keep   A       C     C
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       B     C    D     --soft   B       B     D
+			  --mixed  B       D     D
+			  --hard   D       D     D
+			  --merge  D       D     D
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       B     C    C     --soft   B       B     C
+			  --mixed  B       C     C
+			  --hard   C       C     C
+			  --merge  C       C     C
+			  --keep   B       C     C
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       C     C    D     --soft   B       C     D
+			  --mixed  B       D     D
+			  --hard   D       D     D
+			  --merge (disallowed)
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ B       C     C    C     --soft   B       C     C
+			  --mixed  B       C     C
+			  --hard   C       C     C
+			  --merge  B       C     C
+			  --keep   B       C     C
+....
+
+`reset --merge` is meant to be used when resetting out of a conflicted
+merge. Any mergy operation guarantees that the working tree file that is
+involved in the merge does not have a local change with respect to the index
+before it starts, and that it writes the result out to the working tree. So if
+we see some difference between the index and the target and also
+between the index and the working tree, then it means that we are not
+resetting out from a state that a mergy operation left after failing
+with a conflict. That is why we disallow `--merge` option in this case.
+
+`reset --keep` is meant to be used when removing some of the last
+commits in the current branch while keeping changes in the working
+tree. If there could be conflicts between the changes in the commit we
+want to remove and the changes in the working tree we want to keep,
+the reset is disallowed. That's why it is disallowed if there are both
+changes between the working tree and `HEAD`, and between `HEAD` and the
+target. To be safe, it is also disallowed when there are unmerged
+entries.
+
+The following tables show what happens when there are unmerged
+entries:
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ X       U     A    B     --soft  (disallowed)
+			  --mixed  X       B     B
+			  --hard   B       B     B
+			  --merge  B       B     B
+			  --keep  (disallowed)
+....
+
+....
+working index HEAD target         working index HEAD
+----------------------------------------------------
+ X       U     A    A     --soft  (disallowed)
+			  --mixed  X       A     A
+			  --hard   A       A     A
+			  --merge  A       A     A
+			  --keep  (disallowed)
+....
+
+`X` means any state and `U` means an unmerged index.
+
+GIT
+---
+Part of the linkgit:git[1] suite