$ git clone -n https://src.fedoraproject.org/rpms/rust-base64ct.git /var/lib/mock/f38-build-side-43-rust-devel-1409964-31409/root/chroot_tmpdir/scmroot/rust-base64ct
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1409964-31409/root/chroot_tmpdir/scmroot/rust-base64ct'...
$ git fetch origin f51fbd688d6f81defcc4b02adf10935d53c9021f:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-base64ct
 * [new ref]         f51fbd688d6f81defcc4b02adf10935d53c9021f -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f51fbd6 Update to version 1.6.0; Fixes RHBZ#2173450