Create a pair of changes that will be submitted atomically. It will modify

    usage: fx atomic-commit [--no-upload] [--repo <path>]

      --no-upload    Amend the commits but don't push them.
      --repo <path>  Path of the other repository, relative to the Fuchsia
                     checkout. Defaults to vendor/google. The repository must
                     support circular dependencies with fuchsia.git, e.g.
                     third_party/cobalt_config.

[atomic-commit source code](https://cs.opensource.google/fuchsia/fuchsia/+/main:tools/devshell/atomic-commit)