ci: add benchmark-regression-check

Signed-off-by: Zixuan Liu <nodeces@gmail.com>

.travis.yml

@@ -13,3 +13,4 @@ go:
 
 script:
   - make test
+  - bash ./.travis/benchmark-regressions-check.sh

.travis/benchmark-regressions-check.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+
+# visit https://docs.travis-ci.com/user/environment-variables/#default-environment-variables for details
+
+version=$(go version | grep -Eo '[0-9]+\.[0-9]+')
+
+# check environment
+if [[ $TRAVIS_PULL_REQUEST == "false" ]] || [[ $version != "1.14" ]] || [[ $TRAVIS != "true" ]]; then
+  echo "The script runs only on Travis-CI PR events with Golang 1.14"
+  exit 0
+fi
+
+# install jq 1.6
+curl -s -L https://github.com/stedolan/jq/releases/download/jq-1.6/jq-linux64 >./jq
+chmod +x ./jq
+
+# install benchstat
+go get -u golang.org/x/perf/cmd/benchstat
+
+remote_repo="https://github.com/$TRAVIS_REPO_SLUG"
+
+echo "git clone --single-branch --branch ""$TRAVIS_BRANCH"" ""$remote_repo"" old_repo"
+git clone --single-branch --branch "$TRAVIS_BRANCH" "$remote_repo" old_repo
+
+cd old_repo || exit 1
+go test -bench=. -count=3 | tee output.txt
+cd - || exit 1
+
+go test -bench=. -count=3 | tee output.txt
+
+cat <<EOF >body.md
+The computes and compares statistics about benchmarks for ${TRAVIS_PULL_REQUEST_SHA} by [benchstat](https://github.com/golang/perf/tree/master/cmd/benchstat) on Golang 1.14:
+
+\`\`\`
+$(benchstat old_repo/output.txt output.txt | tee benchstat.log)
+\`\`\`
+EOF
+
+URL="https://api.github.com/repos/$TRAVIS_REPO_SLUG/issues/$TRAVIS_PULL_REQUEST/comments"
+
+data='{ "body": '"$(./jq -R -s <body.md)"' }'
+
+echo "request - $URL"
+
+res=$(curl -s \
+  -X POST \
+  "$URL" \
+  -H "Content-Type: application/json" \
+  -H "Authorization: token $GITHUB_TOKEN" \
+  --data "$data")
+
+echo "$res"
+
+url=$(echo "$res" | ./jq -r '.url')
+
+if [[ -z $url || $url == null ]]; then
+  exit 1
+fi