This should work:
WIKIMEDIA_REPOS=/path/where/you/have/your/clones
REPO=$1 # qa/browsertests
PULL=$2 #
https://github.com/brainwane/qa-browsertests.git
TEMP=`mktemp --tmpdir -d pull-request.XXXXXXX`
git clone --reference="$WIKIMEDIA_REPOS/$REPO" "$PULL"
"$TEMP"
cd "$TEMP"
if [ ! -f .gitreview ]; then
cat > .gitreview <<EOF
[gerrit]
host=gerrit.wikimedia.org
port=29418
project=$REPO.git
defaultbranch=master
defaultrebase=0
EOF
fi
git-review -R
rm -rf "$TEMP"