$ git clone -n https://src.fedoraproject.org/rpms/R-colorspace.git /var/lib/mock/f38-build-723924-99307/root/chroot_tmpdir/scmroot/R-colorspace
Cloning into '/var/lib/mock/f38-build-723924-99307/root/chroot_tmpdir/scmroot/R-colorspace'...
$ git fetch origin 5a9a2f2988d1713eeec083f04050c5624b8013c9:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-colorspace
 * [new ref]         5a9a2f2988d1713eeec083f04050c5624b8013c9 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5a9a2f2 R-maint-sig mass rebuild