$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gtk3.git /var/lib/mock/f41-build-1107978-20090/root/chroot_tmpdir/scmroot/rubygem-gtk3
Cloning into '/var/lib/mock/f41-build-1107978-20090/root/chroot_tmpdir/scmroot/rubygem-gtk3'...
$ git fetch origin fbc3621fd617fb8a5d73504cd848a911ee35d02f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gtk3
 * [new ref]         fbc3621fd617fb8a5d73504cd848a911ee35d02f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fbc3621 4.2.2 entry