CERN-PH-CMG/cmg-cmssw — pull request #20 by gpetruc (2014-02-14 10:30:54+00:00)
Title: TTHAnalysis for Susy: analyzer to log into the tree the masses of the Susy particles

You need to add also SimDataFormats/GeneratorProducts/ to your sparse checkout:

cd $CMSSW_BASE
echo SimDataFormats/GeneratorProducts/ >> .git/info/sparse-checkout
git read-tree -mu HEAD

Possibly with a "git stash" before and a "git stash pop" after, if it complains that you have uncommitted changes.