Mercurial changegroup hook triggering a Jenkins job build only if particular branch is changed

jenkins_build_trigger.sh

#!/bin/sh

JENKINS_URL=http://hg.somewhere.net
JENKINS_TOKEN=token
JENKINS_JOB=""

HG_REPOSITORY=/path/to/repository
HG_BRANCH=""
HG_NODE=""

while [[ "$#" -gt 0 ]]; do
    case $1 in
        -j|--job) JENKINS_JOB="$2"; shift ;;
        -b|--branch) HG_BRANCH="$2"; shift ;;
        -n|--node) HG_NODE="$2"; shift ;;
        *) echo "Unknown parameter passed: $1"; exit 1 ;;
    esac
    shift
done

LOG_LINE_COUNT=$(hg log -R $HG_REPOSITORY -r $HG_NODE: -b $HG_BRANCH | wc -l)

if [ $LOG_LINE_COUNT -gt 0 ]
then
    curl --silent $JENKINS_URL/job/$JENKINS_JOB/build?token=$JENKINS_TOKEN
fi