$ git clone -n https://src.fedoraproject.org/rpms/mbedtls.git /var/lib/mock/f40-build-788915-135460/root/chroot_tmpdir/scmroot/mbedtls
Cloning into '/var/lib/mock/f40-build-788915-135460/root/chroot_tmpdir/scmroot/mbedtls'...
$ git fetch origin f8307a0e6aba6e0790cc4f5dd200b1a3eabee29b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mbedtls
 * [new ref]         f8307a0e6aba6e0790cc4f5dd200b1a3eabee29b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f8307a0 Update to 2.28.7