$ git clone -n https://src.fedoraproject.org/rpms/perl-Email-MIME-Kit.git /var/lib/mock/f40-build-2017021-46264/root/chroot_tmpdir/scmroot/perl-Email-MIME-Kit
Cloning into '/var/lib/mock/f40-build-2017021-46264/root/chroot_tmpdir/scmroot/perl-Email-MIME-Kit'...
$ git fetch origin fc55a6a10df057c844474abcc31e2a7ada35ff2c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Email-MIME-Kit
 * [new ref]         fc55a6a10df057c844474abcc31e2a7ada35ff2c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fc55a6a 3.000008 bump (rhbz#2237034)