$ git clone -n https://src.fedoraproject.org/rpms/R-BufferedMatrix.git /var/lib/mock/f42-build-side-110318-58924507-6569303/root/chroot_tmpdir/scmroot/R-BufferedMatrix
Cloning into '/var/lib/mock/f42-build-side-110318-58924507-6569303/root/chroot_tmpdir/scmroot/R-BufferedMatrix'...
$ git fetch origin 822106ec9927078f871a3197459f3a7a0fb8e186:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/R-BufferedMatrix
 * [new ref]         822106ec9927078f871a3197459f3a7a0fb8e186 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 822106e Update to latest version