$ git clone -n https://src.fedoraproject.org/rpms/plasma-welcome.git /var/lib/mock/f42-build-side-1-3566299-46733/root/chroot_tmpdir/scmroot/plasma-welcome
Cloning into '/var/lib/mock/f42-build-side-1-3566299-46733/root/chroot_tmpdir/scmroot/plasma-welcome'...
$ git fetch origin be4825ba7e46f4d8b223dc499d445d5fe37da589:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-welcome
 * [new ref]         be4825ba7e46f4d8b223dc499d445d5fe37da589 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at be4825b 6.4.0