$ git clone -n https://src.fedoraproject.org/rpms/rust-der.git /var/lib/mock/f38-build-side-42-init-devel-1130558-30311/root/chroot_tmpdir/scmroot/rust-der
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-1130558-30311/root/chroot_tmpdir/scmroot/rust-der'...
$ git fetch origin 6261e57039701deae36fa60b1d2a59facf5c91b7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-der
 * [new ref]         6261e57039701deae36fa60b1d2a59facf5c91b7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 6261e57 Update to version 0.7.7; Fixes RHBZ#2218547