Ask HN: Tool to update many Git repos at once

A tool for this is not hard to build. But before doing so, I want to make sure it doesn't yet exist.

We have a bunch of Git repositories with very similar (Java) projects. More often than I care to deal with by hand there are simple configuration updates that I want to apply to all of these projects in a mechanical fashion, create a (same name) branch for all of them, commit, push. Typically, these configuration updates would be easy enough to capture in a sed command or other sort of regex search/replace.

Is there any such tool that I can use for this? (Preferably Linux/cross-platform.) Thanks!