$ git clone -n https://src.fedoraproject.org/rpms/rust-slug.git /var/lib/mock/f40-build-2063766-49167/root/chroot_tmpdir/scmroot/rust-slug
Cloning into '/var/lib/mock/f40-build-2063766-49167/root/chroot_tmpdir/scmroot/rust-slug'...
$ git fetch origin c349339bb7665194701a3eef600f37106de65052:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-slug
 * [new ref]         c349339bb7665194701a3eef600f37106de65052 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c349339 Update to version 0.1.5; Fixes RHBZ#2248167