$ git clone -n https://src.fedoraproject.org/rpms/gnome-shell-extension-gamerzilla.git /var/lib/mock/f38-build-side-42-init-devel-1407219-31287/root/chroot_tmpdir/scmroot/gnome-shell-extension-gamerzilla
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1407219-31287/root/chroot_tmpdir/scmroot/gnome-shell-extension-gamerzilla'...
$ git fetch origin f37610c66b507069fe1a7f4a0b74797de65c54c5:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-shell-extension-gamerzilla
 * [new ref]         f37610c66b507069fe1a7f4a0b74797de65c54c5 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f37610c Initial import (fedora#2231748).