$ git clone -n https://src.fedoraproject.org/rpms/rust-base64_0.12.git /var/lib/mock/f38-build-side-43-rust-devel-1417038-31458/root/chroot_tmpdir/scmroot/rust-base64_0.12
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1417038-31458/root/chroot_tmpdir/scmroot/rust-base64_0.12'...
$ git fetch origin 0f26dba3ef749c9d41c937e3337fcf61242f1112:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-base64_0.12
 * [new ref]         0f26dba3ef749c9d41c937e3337fcf61242f1112 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 0f26dba Regenerate with rust2rpm v24