$ git clone -n https://src.fedoraproject.org/rpms/rubygem-activemodel.git /var/lib/mock/f39-build-1725467-41233/root/chroot_tmpdir/scmroot/rubygem-activemodel
Cloning into '/var/lib/mock/f39-build-1725467-41233/root/chroot_tmpdir/scmroot/rubygem-activemodel'...
$ git fetch origin 0bc00f73c754ac4709a538e10ae712163de495c2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-activemodel
 * [new ref]         0bc00f73c754ac4709a538e10ae712163de495c2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0bc00f7 Enable tests.