Support for a rollback

[bkemper]

The use case is I just merged my feature branch to the "develop" branch with finish and for whatever reason, I need to revert my merge.

$  git rollback 273b1f19 push

Under the hood, I think something like this could work.

git checkout develop
git pull origin develop
git revert  --mainline 1 $1
[[ $2 = 'push' ]] && git push origin develop

Extra Credit

• Support for "master" branch
• Default SHA to HEAD
• Restore feature branch