Git: how to reverse-merge a commit?

To create a new commit that 'undoes' the changes of a past commit, use:

$ git revert <commit-hash>

It's also possible to actually remove a commit from an arbitrary point in the past by rebasing and then resetting, but you really don't want to do that if you have already pushed your commits to another repository (or someone else has pulled from you).

If your previous commit is a merge commit you can run this command

$ git revert -m 1 <commit-hash>

See schacon.github.io/git/howto/revert-a-faulty-merge.txt for proper ways to re-merge an un-merged branch

If I understand you correctly, you're talking about doing a

svn merge -rn:n-1

to back out of an earlier commit, in which case, you're probably looking for

git revert

To revert a merge commit, you need to use: git revert -m <parent number>. So for example, to revert the recent most merge commit using the parent with number 1 you would use:

git revert -m 1 HEAD

To revert a merge commit before the last commit, you would do:

git revert -m 1 HEAD^

Use git show <merge commit SHA1> to see the parents, the numbering is the order they appear e.g. Merge: e4c54b3 4725ad2

git merge documentation: http://schacon.github.com/git/git-merge.html

git merge discussion (confusing but very detailed): http://schacon.github.com/git/howto/revert-a-faulty-merge.txt