$ git clone -n https://src.fedoraproject.org/rpms/gamescope.git /var/lib/mock/f40-build-2375225-60422/root/chroot_tmpdir/scmroot/gamescope
Cloning into '/var/lib/mock/f40-build-2375225-60422/root/chroot_tmpdir/scmroot/gamescope'...
$ git fetch origin e1e904663c0cfb3d13874e36e9b970b421147236:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gamescope
 * [new ref]         e1e904663c0cfb3d13874e36e9b970b421147236 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e1e9046 Rebase to 3.14.0 (Fixes RHBZ#2259316)