$ git clone -n https://src.fedoraproject.org/rpms/rust-git2_0.17.git /var/lib/mock/f40-build-2413615-60564/root/chroot_tmpdir/scmroot/rust-git2_0.17
Cloning into '/var/lib/mock/f40-build-2413615-60564/root/chroot_tmpdir/scmroot/rust-git2_0.17'...
$ git fetch origin 141b88836dbf4387343da5385c1f8dac50e6881c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-git2_0.17
 * [new ref]         141b88836dbf4387343da5385c1f8dac50e6881c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 141b888 compat package no longer needed