How do I reverse a specific hunk of a commit in git?

Question

I'm wondering if there is a way to quickly reverse specific hunk of a commit.

I can generate a diff between two commits or HEAD to see the difference.

How do I reverse just one of those hunks (or better yet, a set of specific hunks)?

Cricoid

Answer 1

git checkout -p $REF -- path/to/file

e.g.,

git checkout -p HEAD^ myfile

Where $REF is a ref name or commit ID that specifies the commit you want to take the file state from. For example, to selectively revert changes made in the last commit, use HEAD^.

Coeternity

More precisely, that will let you selectively check out versions of content from the previous commit; changes between your current commit and the work tree will also be discarded. – Polonium

Yes I've done this that before. But this reverts back all the changes? I'm looking to revert back only some of the changes. – Cricoid

@DKinzer: No, the -p option will let you interactively select hunks to apply to your working tree. – Coeternity

No problem. Note that a lot of git commits (add, checkout, reset, etc.) will take the -p option this way and will let you pick which hunks to act on. This is really handy when two hunks in the same file should go into different commits. – Coeternity

I'm new to git and so far only knew about -i for selectively choosing commits when doing a rebase. I think the -p option will be very useful to me. – Cricoid

In order to remove hunks, select y when prompted for each hunk. This will produce a staged diff on top of your previous commit without modifying it. You can then view the diff by unstaging it (git reset <file>) then git diff. Finally, you can merge it into your previous commit via git commit --amend <file>). – Ottillia

Answer 2

To revert one or more hunks from specific commit(s) do like this - using add -p in essence:

git revert --no-commit <commit>…​ 
git reset                              # unstage things
git add -p [OPTIONS] [<pathspec>…​]     # choose hunks interactively
git restore .                          # wipe the rest (in root directory)
... maybe further changes ...
git commit [--fixup] ...

Future git versions may support git revert -p directly...

Note: Methods like git checkout/restore -p ... do not consistently revert hunks from a specific commit but go to pick parts from a certain file state - possibly loosing changes in other later commits.

Kulseth

Answer 3

git difftool $REF -- /path/to/file

where $REF is a ref name or commit ID that specifies the commit you want to take the file state from. For example, to selectively revert changes made in the last commit, use HEAD^.

This question was already answered by @cdhowie, but I find it somewhat nicer to use an interactive difftool like meld to selectively restore old hunks/lines of code, especially if there is a newly-introduced, hard-to-find bug in the code.

Asuncionasunder

Answer 4

To recover a deleted file from a previous commit I used the answer here:

Find and restore a deleted file in a Git repository

git checkout <deleting_commit>^ -- <file_path>

Rattat

Answer 5

The way I like to do this is to use:

1. git rebase -i HEAD~n where 'n' is the number of commits back.
2. Use 'edit', on the commit you want to remove the hunk from.
3. Follow this with git add -p or manual edits.
4. git commit --amend.
5. git rebase --continue to end the rebase.

Klansman