$ git clone -n https://src.fedoraproject.org/rpms/rubygem-nokogiri.git /var/lib/mock/f45-build-35085-693/root/chroot_tmpdir/scmroot/rubygem-nokogiri
Cloning into '/var/lib/mock/f45-build-35085-693/root/chroot_tmpdir/scmroot/rubygem-nokogiri'...
$ git fetch origin 121d6be935c625fa76952c85062b8b430065b7f4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-nokogiri
 * [new ref]         121d6be935c625fa76952c85062b8b430065b7f4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 121d6be Rebuilt for libxml-2.5.4