$ git clone -n https://src.fedoraproject.org/rpms/rust-bpaf.git /var/lib/mock/f42-build-side-1-3583667-46890/root/chroot_tmpdir/scmroot/rust-bpaf
Cloning into '/var/lib/mock/f42-build-side-1-3583667-46890/root/chroot_tmpdir/scmroot/rust-bpaf'...
$ git fetch origin 54b485f4b9de8152bc061269e149c65776772c14:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-bpaf
 * [new ref]         54b485f4b9de8152bc061269e149c65776772c14 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 54b485f Update to version 0.9.20; Fixes RHBZ#2368462