git/Documentation/git-cherry-pick.txt
Brian Lyles ec79d763de cherry-pick: add --empty for more robust redundant commit handling
As with git-rebase(1) and git-am(1), git-cherry-pick(1) can result in a
commit being made redundant if the content from the picked commit is
already present in the target history. However, git-cherry-pick(1) does
not have the same options available that git-rebase(1) and git-am(1) have.

There are three things that can be done with these redundant commits:
drop them, keep them, or have the cherry-pick stop and wait for the user
to take an action. git-rebase(1) has the `--empty` option added in commit
e98c4269c8 (rebase (interactive-backend): fix handling of commits that
become empty, 2020-02-15), which handles all three of these scenarios.
Similarly, git-am(1) got its own `--empty` in 7c096b8d61 (am: support
--empty=<option> to handle empty patches, 2021-12-09).

git-cherry-pick(1), on the other hand, only supports two of the three
possiblities: Keep the redundant commits via `--keep-redundant-commits`,
or have the cherry-pick fail by not specifying that option. There is no
way to automatically drop redundant commits.

In order to bring git-cherry-pick(1) more in-line with git-rebase(1) and
git-am(1), this commit adds an `--empty` option to git-cherry-pick(1). It
has the same three options (keep, drop, and stop), and largely behaves
the same. The notable difference is that for git-cherry-pick(1), the
default will be `stop`, which maintains the current behavior when the
option is not specified.

Like the existing `--keep-redundant-commits`, `--empty=keep` will imply
`--allow-empty`.

The `--keep-redundant-commits` option will be documented as a deprecated
synonym of `--empty=keep`, and will be supported for backwards
compatibility for the time being.

Signed-off-by: Brian Lyles <brianmlyles@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2024-03-25 16:45:41 -07:00

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git-cherry-pick(1)
==================
NAME
----
git-cherry-pick - Apply the changes introduced by some existing commits
SYNOPSIS
--------
[verse]
'git cherry-pick' [--edit] [-n] [-m <parent-number>] [-s] [-x] [--ff]
[-S[<keyid>]] <commit>...
'git cherry-pick' (--continue | --skip | --abort | --quit)
DESCRIPTION
-----------
Given one or more existing commits, apply the change each one
introduces, recording a new commit for each. This requires your
working tree to be clean (no modifications from the HEAD commit).
When it is not obvious how to apply a change, the following
happens:
1. The current branch and `HEAD` pointer stay at the last commit
successfully made.
2. The `CHERRY_PICK_HEAD` ref is set to point at the commit that
introduced the change that is difficult to apply.
3. Paths in which the change applied cleanly are updated both
in the index file and in your working tree.
4. For conflicting paths, the index file records up to three
versions, as described in the "TRUE MERGE" section of
linkgit:git-merge[1]. The working tree files will include
a description of the conflict bracketed by the usual
conflict markers `<<<<<<<` and `>>>>>>>`.
5. No other modifications are made.
See linkgit:git-merge[1] for some hints on resolving such
conflicts.
OPTIONS
-------
<commit>...::
Commits to cherry-pick.
For a more complete list of ways to spell commits, see
linkgit:gitrevisions[7].
Sets of commits can be passed but no traversal is done by
default, as if the `--no-walk` option was specified, see
linkgit:git-rev-list[1]. Note that specifying a range will
feed all <commit>... arguments to a single revision walk
(see a later example that uses 'maint master..next').
-e::
--edit::
With this option, 'git cherry-pick' will let you edit the commit
message prior to committing.
--cleanup=<mode>::
This option determines how the commit message will be cleaned up before
being passed on to the commit machinery. See linkgit:git-commit[1] for more
details. In particular, if the '<mode>' is given a value of `scissors`,
scissors will be appended to `MERGE_MSG` before being passed on in the case
of a conflict.
-x::
When recording the commit, append a line that says
"(cherry picked from commit ...)" to the original commit
message in order to indicate which commit this change was
cherry-picked from. This is done only for cherry
picks without conflicts. Do not use this option if
you are cherry-picking from your private branch because
the information is useless to the recipient. If on the
other hand you are cherry-picking between two publicly
visible branches (e.g. backporting a fix to a
maintenance branch for an older release from a
development branch), adding this information can be
useful.
-r::
It used to be that the command defaulted to do `-x`
described above, and `-r` was to disable it. Now the
default is not to do `-x` so this option is a no-op.
-m <parent-number>::
--mainline <parent-number>::
Usually you cannot cherry-pick a merge because you do not know which
side of the merge should be considered the mainline. This
option specifies the parent number (starting from 1) of
the mainline and allows cherry-pick to replay the change
relative to the specified parent.
-n::
--no-commit::
Usually the command automatically creates a sequence of commits.
This flag applies the changes necessary to cherry-pick
each named commit to your working tree and the index,
without making any commit. In addition, when this
option is used, your index does not have to match the
HEAD commit. The cherry-pick is done against the
beginning state of your index.
+
This is useful when cherry-picking more than one commits'
effect to your index in a row.
-s::
--signoff::
Add a `Signed-off-by` trailer at the end of the commit message.
See the signoff option in linkgit:git-commit[1] for more information.
-S[<keyid>]::
--gpg-sign[=<keyid>]::
--no-gpg-sign::
GPG-sign commits. The `keyid` argument is optional and
defaults to the committer identity; if specified, it must be
stuck to the option without a space. `--no-gpg-sign` is useful to
countermand both `commit.gpgSign` configuration variable, and
earlier `--gpg-sign`.
--ff::
If the current HEAD is the same as the parent of the
cherry-pick'ed commit, then a fast forward to this commit will
be performed.
--allow-empty::
By default, cherry-picking an empty commit will fail,
indicating that an explicit invocation of `git commit
--allow-empty` is required. This option overrides that
behavior, allowing empty commits to be preserved automatically
in a cherry-pick. Note that when "--ff" is in effect, empty
commits that meet the "fast-forward" requirement will be kept
even without this option. Note also, that use of this option only
keeps commits that were initially empty (i.e. the commit recorded the
same tree as its parent). Commits which are made empty due to a
previous commit will cause the cherry-pick to fail. To force the
inclusion of those commits, use `--empty=keep`.
--allow-empty-message::
By default, cherry-picking a commit with an empty message will fail.
This option overrides that behavior, allowing commits with empty
messages to be cherry picked.
--empty=(drop|keep|stop)::
How to handle commits being cherry-picked that are redundant with
changes already in the current history.
+
--
`drop`;;
The commit will be dropped.
`keep`;;
The commit will be kept. Implies `--allow-empty`.
`stop`;;
The cherry-pick will stop when the commit is applied, allowing
you to examine the commit. This is the default behavior.
--
+
Note that `--empty=drop` and `--empty=stop` only specify how to handle a
commit that was not initially empty, but rather became empty due to a previous
commit. Commits that were initially empty will still cause the cherry-pick to
fail unless one of `--empty=keep` or `--allow-empty` are specified.
+
--keep-redundant-commits::
Deprecated synonym for `--empty=keep`.
--strategy=<strategy>::
Use the given merge strategy. Should only be used once.
See the MERGE STRATEGIES section in linkgit:git-merge[1]
for details.
-X<option>::
--strategy-option=<option>::
Pass the merge strategy-specific option through to the
merge strategy. See linkgit:git-merge[1] for details.
include::rerere-options.txt[]
SEQUENCER SUBCOMMANDS
---------------------
include::sequencer.txt[]
EXAMPLES
--------
`git cherry-pick master`::
Apply the change introduced by the commit at the tip of the
master branch and create a new commit with this change.
`git cherry-pick ..master`::
`git cherry-pick ^HEAD master`::
Apply the changes introduced by all commits that are ancestors
of master but not of HEAD to produce new commits.
`git cherry-pick maint next ^master`::
`git cherry-pick maint master..next`::
Apply the changes introduced by all commits that are
ancestors of maint or next, but not master or any of its
ancestors. Note that the latter does not mean `maint` and
everything between `master` and `next`; specifically,
`maint` will not be used if it is included in `master`.
`git cherry-pick master~4 master~2`::
Apply the changes introduced by the fifth and third last
commits pointed to by master and create 2 new commits with
these changes.
`git cherry-pick -n master~1 next`::
Apply to the working tree and the index the changes introduced
by the second last commit pointed to by master and by the last
commit pointed to by next, but do not create any commit with
these changes.
`git cherry-pick --ff ..next`::
If history is linear and HEAD is an ancestor of next, update
the working tree and advance the HEAD pointer to match next.
Otherwise, apply the changes introduced by those commits that
are in next but not HEAD to the current branch, creating a new
commit for each new change.
`git rev-list --reverse master -- README | git cherry-pick -n --stdin`::
Apply the changes introduced by all commits on the master
branch that touched README to the working tree and index,
so the result can be inspected and made into a single new
commit if suitable.
The following sequence attempts to backport a patch, bails out because
the code the patch applies to has changed too much, and then tries
again, this time exercising more care about matching up context lines.
------------
$ git cherry-pick topic^ <1>
$ git diff <2>
$ git cherry-pick --abort <3>
$ git cherry-pick -Xpatience topic^ <4>
------------
<1> apply the change that would be shown by `git show topic^`.
In this example, the patch does not apply cleanly, so
information about the conflict is written to the index and
working tree and no new commit results.
<2> summarize changes to be reconciled
<3> cancel the cherry-pick. In other words, return to the
pre-cherry-pick state, preserving any local modifications
you had in the working tree.
<4> try to apply the change introduced by `topic^` again,
spending extra time to avoid mistakes based on incorrectly
matching context lines.
SEE ALSO
--------
linkgit:git-revert[1]
GIT
---
Part of the linkgit:git[1] suite