$ git clone -n https://src.fedoraproject.org/rpms/rust-maildir.git /var/lib/mock/f39-build-1534600-36233/root/chroot_tmpdir/scmroot/rust-maildir
Cloning into '/var/lib/mock/f39-build-1534600-36233/root/chroot_tmpdir/scmroot/rust-maildir'...
$ git fetch origin d1e385e2a36b25de0db5005373f36e28ff1744e3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-maildir
 * [new ref]         d1e385e2a36b25de0db5005373f36e28ff1744e3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at d1e385e Update to version 0.6.4; Fixes RHBZ#1912233