$ git clone -n https://src.fedoraproject.org/rpms/rust-siphasher.git /var/lib/mock/f40-build-2643521-66488/root/chroot_tmpdir/scmroot/rust-siphasher
Cloning into '/var/lib/mock/f40-build-2643521-66488/root/chroot_tmpdir/scmroot/rust-siphasher'...
$ git fetch origin 05d84793a7906dece31de7e4aec5662b0b644ac1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-siphasher
 * [new ref]         05d84793a7906dece31de7e4aec5662b0b644ac1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 05d8479 Update to version 1.0.1; Fixes RHBZ#2269988