Harden benchmark script against pull request changes (#185)

Require a new `TARGET` variable specifying the expected SHA of the
commit at the HEAD of the pull request when running the benchmark
script for pull requests.

Use shallow clone in benchmark script.

For consistency, rename the BRANCH parameter from use case 1 in the
benchmark script to BASE.

Author: richardlau

benchmarks/community-benchmark/run.sh

@@ -1,4 +1,23 @@
 #!/bin/bash
+function assertShaLike() {
+    local shaVarName="${1}"
+    local sha="${!1}"
+    if [ -z "${sha}" ] || ! echo "${sha}" | grep -qE '^[0-9a-fA-F]+$'; then
+        echo "${shaVarName} (${sha}) does not look like a commit SHA"
+        exit
+    fi
+}
+
+function assertMatchesPullRequest() {
+    local shaVarName="${1}"
+    local sha="${!1}"
+    local pr_id="${!2}"
+    if [[ ! "$(git ls-remote origin refs/pull/${pr_id}/head)" =~ ^${sha}.*refs/pull/${pr_id}/head$ ]]; then
+        echo "${shaVarName} (${sha}) does not match HEAD for pull request ${pr_id}"
+        exit
+    fi
+}
+
 function mandatory() {
     if [ -z "${!1}" ]; then
         echo "${1} not set"
@@ -25,8 +44,9 @@ 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 "BASE = the branch the test should be based off. e.g. master"
 echo "PULL_ID = the pull request that contains changes to test"
+echo "TARGET = the SHA of the commit HEAD that contains changes to test"
 echo "-------------------------------------------------------------"
 echo "Use case 2: We want to compare two branches, tags or commits."
 echo "To run this, declare:"
@@ -48,8 +68,10 @@ if [ -z $PULL_ID ]; then
 	mandatory TARGET
 else
 	export USE_CASE=1
-	mandatory BRANCH
+	mandatory BASE
 	mandatory PULL_ID
+	mandatory TARGET
+	assertShaLike TARGET
 fi
 mandatory CATEGORY
 optional RUNS 
@@ -59,11 +81,13 @@ 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
+git clone --depth=1 https://github.com/nodejs/node.git
 cd node
 case $USE_CASE in
 1)
-	git checkout $BRANCH
+	# Validate TARGET and pull request HEAD are consistent
+	assertMatchesPullRequest TARGET PULL_ID
+	git checkout $BASE
 	;;
 2)
 	git checkout $BASE
@@ -81,7 +105,7 @@ mv out/Release/node ./node-master
 # build pr
 case $USE_CASE in
 1)
-        curl -L https://github.com/nodejs/node/pull/${PULL_ID}.patch|git apply -3
+        curl -L "https://github.com/nodejs/node/compare/$(git rev-parse HEAD)...${TARGET}.patch"|git apply -3
 	;;
 2)
 	git checkout $TARGET