$ git clone -n https://src.fedoraproject.org/rpms/gamescope.git /var/lib/mock/f39-build-1543812-36590/root/chroot_tmpdir/scmroot/gamescope
Cloning into '/var/lib/mock/f39-build-1543812-36590/root/chroot_tmpdir/scmroot/gamescope'...
$ git fetch origin 5a1e0309da7cd049f7709f79a95a9616373b1602:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gamescope
 * [new ref]         5a1e0309da7cd049f7709f79a95a9616373b1602 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5a1e030 Rebase to 3.12.7 (Fixes RHBZ#2242995)