Sometimes using git replace followed by git filter-branch (so that you wind up with a valid history with all hashes correct) is the best way to get the history

Sometimes using git replace followed by git filter-branch (so that you wind up with a valid history with all hashes correct) is the best way to get the history you want. This is usually in really extreme cases. ie at Loggly we had a frontend repo that we wound up splitting into media, templates, and webapp repos, and then later decided to put back into a frontend repo. The former operation was pretty easy with filter-branch, but for the latter, I used replace + filter-branch.