$ git clone -n https://src.fedoraproject.org/rpms/maturin.git /var/lib/mock/f42-build-side-1-3589336-46957/root/chroot_tmpdir/scmroot/maturin
Cloning into '/var/lib/mock/f42-build-side-1-3589336-46957/root/chroot_tmpdir/scmroot/maturin'...
$ git fetch origin b03f22b8740d81e807f8455c6bdb364df45b1b2a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/maturin
 * [new ref]         b03f22b8740d81e807f8455c6bdb364df45b1b2a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b03f22b Update to version 1.8.6; Fixes RHBZ#2365325