$ git clone -n https://src.fedoraproject.org/rpms/exim.git /var/lib/mock/f41-build-816495-150225/root/chroot_tmpdir/scmroot/exim
Cloning into '/var/lib/mock/f41-build-816495-150225/root/chroot_tmpdir/scmroot/exim'...
$ git fetch origin f75cf0315f6c7dc554f869836fa8991f781404b4:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/exim
 * [new ref]         f75cf0315f6c7dc554f869836fa8991f781404b4 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f75cf03 Perl 5.40 rebuild