I would like to extend git such that you can check out a commit, amend it, rebase all descendants onto the amended commit, and update any branches accordingly.

I would like to extend git such that you can check out a commit, amend it, rebase all descendants onto the amended commit, and update any branches accordingly. Effectively like `rebase -i` but not modal. This requires keeping some state around. libgit2 is a nice pointer, I'll check that out. (hg users will recognize this as "restacking.")