Prototype for running a subset of benchmarks on a pull request (#58)

Benchmarking: Commit script for running subset of benchmarks to test a PR

Squashing commits:
* Adding prototype for running test against a pr
* Setting to use default RUNS too
* Addressing points and also setting default runs to 30 to match the scripts in node/benchmark
*  Updating usage
* Rework to make it less hacky

run.sh

@@ -0,0 +1,97 @@
+#!/bin/bash
+function mandatory() {
+    if [ -z "${!1}" ]; then
+        echo "${1} not set"
+        usage
+        exit
+    fi
+}
+
+function optional() {
+    if [ -z "${!1}" ]; then
+        echo -n "${1} not set (ok)"
+        if [ -n "${2}" ]; then
+            echo -n ", default is: ${2}"
+            export ${1}="${2}"
+        fi
+        echo ""
+    fi
+}
+function usage(){
+echo "Usage:"
+
+echo "This script has two use cases:"
+echo "Use case 1: We want to test the impact of a PR on a branch."
+echo "To run this, declare:"
+echo "The script expects the following variables to be set:"
+echo "CATEGORY = a category of tests to run - folders in benchmark/"
+echo "BRANCH = the branch the test should be based off. e.g. master"
+echo "PULL_ID = the pull request that contains changes to test"
+echo "-------------------------------------------------------------"
+echo "Use case 2: We want to compare two branches, tags or commits."
+echo "To run this, declare:"
+echo "CATEGORY = a category of tests to run - folders in benchmark/"
+echo "BASE = the branch/tag/commit the test should be based off. e.g. master"
+echo "TARGET = the branch/tag/commit to compare against base"
+echo "-------------------------------------------------------------"
+echo "The following are optional across both use cases"
+echo "RUNS = defaults to empty"
+echo "FILTER = defaults to empty"
+echo "MACHINE_THREADS - used for building node. Defaults to all threads on machine"
+
+}
+
+if [ -z $PULL_ID ]; then
+#PULL_ID isn't declared. Therefore we are probably in use case #2
+	export USE_CASE=2
+	mandatory BASE
+	mandatory TARGET
+else
+	export USE_CASE=1
+	mandatory BRANCH
+	mandatory PULL_ID
+fi
+mandatory CATEGORY
+optional RUNS 
+optional FILTER
+getMACHINE_THREADS=`cat /proc/cpuinfo |grep processor|tail -n1|awk {'print $3'}`
+let getMACHINE_THREADS=getMACHINE_THREADS+1 #getting threads this way is 0 based. Add one
+optional MACHINE_THREADS $getMACHINE_THREADS
+rm -rf node
+git clone https://github.com/nodejs/node.git
+cd node
+case $USE_CASE in
+1)
+	git checkout $BRANCH
+	;;
+2)
+	git checkout $BASE
+	;;
+esac
+
+# build master
+./configure
+make -j${MACHINE_THREADS}
+mv out/Release/node ./node-master
+
+# build pr
+case $USE_CASE in
+1)
+        curl https://patch-diff.githubusercontent.com/raw/nodejs/node/pull/${PULL_ID}.patch|git apply
+	;;
+2)
+	git checkout $TARGET
+	;;
+esac
+./configure
+make -j${MACHINE_THREADS}
+mv out/Release/node ./node-pr
+if [ -n "$FILTER" ]; then
+	FILTER="--filter ${FILTER}"
+fi
+if [ -n "$RUNS" ]; then
+	RUNS="--runs ${RUNS}"
+fi
+# run benchmark
+./node-master benchmark/compare.js --old ./node-master --new ./node-pr $FILTER $RUNS -- $CATEGORY | tee output.csv
+cat output.csv | Rscript benchmark/compare.R