$ git clone -n https://src.fedoraproject.org/rpms/rubygem-activesupport.git /var/lib/mock/f40-build-2033481-47808/root/chroot_tmpdir/scmroot/rubygem-activesupport
Cloning into '/var/lib/mock/f40-build-2033481-47808/root/chroot_tmpdir/scmroot/rubygem-activesupport'...
$ git fetch origin 28b148f2fbab5763b53c06beaa210b8fb1d30ef3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-activesupport
 * [new ref]         28b148f2fbab5763b53c06beaa210b8fb1d30ef3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 28b148f Add forgotten changelog entry for 0b918bc.