$ git clone -n https://src.fedoraproject.org/rpms/rust-base64ct.git /var/lib/mock/f43-build-59075515-6570862/root/chroot_tmpdir/scmroot/rust-base64ct
Cloning into '/var/lib/mock/f43-build-59075515-6570862/root/chroot_tmpdir/scmroot/rust-base64ct'...
$ git fetch origin b87565065efc98dd2fcb7ba575b3ce81ac678ab0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-base64ct
 * [new ref]         b87565065efc98dd2fcb7ba575b3ce81ac678ab0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b875650 Update to version 1.7.3; Fixes RHBZ#2351242