$ git clone -n https://src.fedoraproject.org/rpms/plasma-welcome.git /var/lib/mock/f42-build-side-1-3499065-45964/root/chroot_tmpdir/scmroot/plasma-welcome
Cloning into '/var/lib/mock/f42-build-side-1-3499065-45964/root/chroot_tmpdir/scmroot/plasma-welcome'...
$ git fetch origin 3ee63b0a168c33c47831f2d347953d22802de148:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/plasma-welcome
 * [new ref]         3ee63b0a168c33c47831f2d347953d22802de148 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3ee63b0 6.3.4