$ git clone -n https://src.fedoraproject.org/rpms/gnome-shell.git /var/lib/mock/f42-build-side-1-3497869-45961/root/chroot_tmpdir/scmroot/gnome-shell
Cloning into '/var/lib/mock/f42-build-side-1-3497869-45961/root/chroot_tmpdir/scmroot/gnome-shell'...
$ git fetch origin 319b5872fb089e15d4a77180933cdee88df9e48b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gnome-shell
 * [new ref]         319b5872fb089e15d4a77180933cdee88df9e48b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 319b587 Update to 48.1