$ git clone -n https://src.fedoraproject.org/rpms/fgrun.git /var/lib/mock/f38-build-side-42-init-devel-690136-26811/root/chroot_tmpdir/scmroot/fgrun
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-690136-26811/root/chroot_tmpdir/scmroot/fgrun'...
$ git fetch origin c1fa29a449c26c36f54475b5c595c3f4d9031ab1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/fgrun
 * [new ref]         c1fa29a449c26c36f54475b5c595c3f4d9031ab1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c1fa29a rebuild with newer SimGear