$ git clone -n https://src.fedoraproject.org/rpms/mkvtoolnix.git /var/lib/mock/f40-build-2242841-53669/root/chroot_tmpdir/scmroot/mkvtoolnix
Cloning into '/var/lib/mock/f40-build-2242841-53669/root/chroot_tmpdir/scmroot/mkvtoolnix'...
$ git fetch origin e0df2a31b529ce10878f7d738b68db77e758b6b6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mkvtoolnix
 * [new ref]         e0df2a31b529ce10878f7d738b68db77e758b6b6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e0df2a3 Merge branch 'f39' into rawhide