$ git clone -n https://src.fedoraproject.org/rpms/shim.git /var/lib/mock/f42-build-3350043-45010/root/chroot_tmpdir/scmroot/shim
Cloning into '/var/lib/mock/f42-build-3350043-45010/root/chroot_tmpdir/scmroot/shim'...
$ git fetch origin 7b08c421ed4dbca88af0cbaabb73332d08944c86:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/shim
 * [new ref]         7b08c421ed4dbca88af0cbaabb73332d08944c86 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 7b08c42 Fix fbx64/mmx64 signing.