$ git clone -n https://src.fedoraproject.org/rpms/jstest-gtk.git /var/lib/mock/f39-build-1544069-36613/root/chroot_tmpdir/scmroot/jstest-gtk
Cloning into '/var/lib/mock/f39-build-1544069-36613/root/chroot_tmpdir/scmroot/jstest-gtk'...
$ git fetch origin c9e1fd105355262c578c43496852db244a2daca1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jstest-gtk
 * [new ref]         c9e1fd105355262c578c43496852db244a2daca1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c9e1fd1 Initial (rh#2241551)