$ git clone -n https://src.fedoraproject.org/rpms/ffmpeg.git /var/lib/mock/f40-build-788882-135454/root/chroot_tmpdir/scmroot/ffmpeg
Cloning into '/var/lib/mock/f40-build-788882-135454/root/chroot_tmpdir/scmroot/ffmpeg'...
$ git fetch origin 45f69ccd8a92177fba1893ed9d054fc83b1a8ffd:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/ffmpeg
 * [new ref]         45f69ccd8a92177fba1893ed9d054fc83b1a8ffd -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 45f69cc Rebuild for libvpx 1.14.x