$ git clone -n https://src.fedoraproject.org/rpms/rust-tokio-core.git /var/lib/mock/f41-build-side-1-3134951-39764/root/chroot_tmpdir/scmroot/rust-tokio-core
Cloning into '/var/lib/mock/f41-build-side-1-3134951-39764/root/chroot_tmpdir/scmroot/rust-tokio-core'...
$ git fetch origin 9b623979ffc745aac87c9ef590d2adec9c9eae3b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-tokio-core
 * [new ref]         9b623979ffc745aac87c9ef590d2adec9c9eae3b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 9b62397 no longer needed - superseded by tokio