$ git clone -n https://src.fedoraproject.org/rpms/rust-mio.git /var/lib/mock/f45-build-43236-801/root/chroot_tmpdir/scmroot/rust-mio
Cloning into '/var/lib/mock/f45-build-43236-801/root/chroot_tmpdir/scmroot/rust-mio'...
$ git fetch origin f1a85cb56dc2970a058675f627ef059427c731b2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-mio
 * [new ref]         f1a85cb56dc2970a058675f627ef059427c731b2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f1a85cb Update to version 1.2.3; Fixes RHBZ#2527419