test.bash: add script for comprehensive testing

This script is not currently executed by Try-Bots since they do not have the
necessary infrastructure, yet. Instead, this script is intended to be ran as
a pre-commit hook on each contributor's workstation.

The test.bash script works on both Darwin and Linux and tests the repository
across a variety of Go toolchains. The toolchains are downloaded and built
into their own versioned directories and cached. Subsequent runs of the script
only need to run the tests.

Change-Id: Id87841ed42da422ab2e966ea073255ba866c80f7
Reviewed-on: https://go-review.googlesource.com/127826
Reviewed-by: Herbie Ong <herbie@google.com>

test.bash

@@ -0,0 +1,65 @@
+#!/bin/bash
+# Copyright 2018 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+# Create a test directory.
+# The Go and protobuf toolchains used for testing will be cached here.
+TEST_DIR=/tmp/golang-protobuf-test
+if [ ! -d $TEST_DIR ]; then
+	echo "mkdir $TEST_DIR"
+	mkdir -p $TEST_DIR
+fi
+cd $TEST_DIR
+
+# Download and build the protobuf toolchain.
+# We avoid downloading the pre-compiled binaries since they do not contain
+# the conformance test runner.
+PROTOBUF_VERSION=3.6.1
+PROTOBUF_DIR="protobuf-$PROTOBUF_VERSION"
+if [ ! -d $PROTOBUF_DIR ]; then
+	echo "download and build $PROTOBUF_DIR"
+	(curl -s -L https://github.com/google/protobuf/releases/download/v$PROTOBUF_VERSION/protobuf-all-$PROTOBUF_VERSION.tar.gz | tar -zxf -) || exit 1
+	(cd $PROTOBUF_DIR && ./configure && make && cd conformance && make) || exit 1
+fi
+
+# Download each Go toolchain version.
+GO_VERSIONS=(1.9.7 1.10.3 1.11beta3)
+for GO_VERSION in ${GO_VERSIONS[@]}; do
+	GO_DIR=go$GO_VERSION
+	if [ ! -d $GO_DIR ]; then
+		echo "download $GO_DIR"
+		GOOS=$(uname | tr '[:upper:]' '[:lower:]')
+		(mkdir $GO_DIR && curl -s -L https://dl.google.com/go/$GO_DIR.$GOOS-amd64.tar.gz | tar -zxf - -C $GO_DIR --strip-components 1) || exit 1
+	fi
+done
+
+# Setup GOPATH for pre-module support.
+MODULE_PATH=$(grep '^module ' $REPO_ROOT/go.mod | cut -d " " -f 2)
+if [ ! -d gopath/src/$MODULE_PATH ]; then
+	mkdir -p gopath/src/$(dirname $MODULE_PATH)
+	(cd gopath/src/$(dirname $MODULE_PATH) && ln -s $REPO_ROOT $(basename $MODULE_PATH))
+fi
+export GOPATH=$TEST_DIR/gopath
+
+# Run tests across every supported version of Go.
+FAIL=0
+for GO_VERSION in ${GO_VERSIONS[@]}; do
+	export GOROOT=$TEST_DIR/go$GO_VERSION
+	GO_BIN=go$GO_VERSION/bin/go
+	function go_build() {
+		echo "$GO_BIN build $@"
+		(cd $GOPATH/src/$MODULE_PATH && $TEST_DIR/$GO_BIN build $@) || FAIL=1
+	}
+	function go_test() {
+		echo "$GO_BIN test $@"
+		(cd $GOPATH/src/$MODULE_PATH && $TEST_DIR/$GO_BIN test $@) || FAIL=1
+	}
+
+	go_build ./...
+	go_test -race ./...
+	go_test -race -tags proto1_legacy ./...
+done
+exit $FAIL