$ git clone -n https://src.fedoraproject.org/rpms/gamescope.git /var/lib/mock/f40-build-2539235-61857/root/chroot_tmpdir/scmroot/gamescope
Cloning into '/var/lib/mock/f40-build-2539235-61857/root/chroot_tmpdir/scmroot/gamescope'...
$ git fetch origin 78708e6cbab96eb2c945a213ddb9b16ea8688a64:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gamescope
 * [new ref]         78708e6cbab96eb2c945a213ddb9b16ea8688a64 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 78708e6 Rebase to 3.14.2 (Fixes RHBZ#2265459)