$ git clone -n https://src.fedoraproject.org/rpms/rust-bstr.git /var/lib/mock/f40-build-2081170-49749/root/chroot_tmpdir/scmroot/rust-bstr
Cloning into '/var/lib/mock/f40-build-2081170-49749/root/chroot_tmpdir/scmroot/rust-bstr'...
$ git fetch origin bf40c7e13719c39edcaea936521d48ad6159eac6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-bstr
 * [new ref]         bf40c7e13719c39edcaea936521d48ad6159eac6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bf40c7e Update to version 1.8.0; Fixes RHBZ#2248937