Monorepo flow: Roll back all filesystem changes if error encountered

[mcmire]

It is possible for an error to occur while making changes to a monorepo. For instance, as we are updating the changelog for each package, auto-changelog will call git fetch --tags to get the latest tags for the repo. Admittedly, it should probably only do this once at the beginning, but regardless, if this fails for a particular package, but we have made changes to other packages, then the tool will completely abort and leave the repo in a dirty state. We should see if we can roll back all of the filesystem changes if this occurs.