Document and automate parts of the release process (#666)

We currently have an undocumented release process. Document the
different steps and try to automate parts.

The version bumping script is just one part of the process, in future
we'll want to automate the branch/tags as well as updating the release
on GitHub.

Author: prashantv

RELEASE.md

@@ -0,0 +1,52 @@
+Release process
+===============
+
+This document outlines how to create a release of tchannel-go
+
+1.  Set up some environment variables for use later.
+
+    ```
+    # This is the version being released.
+    $ VERSION=1.8.0
+    ```
+
+2.  Make sure you have the latest dev and create a branch off it.
+
+    ```
+    $ git checkout dev
+    $ git pull
+	  $ git checkout release
+    ```
+
+3.  Update the `CHANGELOG.md` and `version.go` files.
+
+    ```
+    $ go run ./scripts/vbumper/main.go --version $VERSION
+    ```
+
+4.  Clean up the `CHANGELOG.md` to only mention noteworthy changes for users.
+
+5.  Commit changes and create a PR against `dev` to prepare for release.
+
+6.  Once the release PR has been accepted, run the following to release.
+
+    ```
+    $ git checkout master
+    $ git pull
+    $ git merge dev
+    $ git tag -a "v$VERSION" -m "v$VERSION"
+    $ git push origin master v$VERSION
+    ```
+
+7.  Go to <https://github.com/uber/tchannel-go/tags> and edit the release notes.
+    Copy changelog entries for this release and set the name to `v$VERSION`.
+
+8.  Switch back to development.
+
+    ```
+    $ git checkout dev
+    $ git merge master
+    $ go run ./scripts/vbumper/main.go --version ${VERSION}-dev --skip-changelog
+    $ git commit -am "Back to development"
+    $ git push
+    ```

scripts/vbumper/main.go

@@ -0,0 +1,166 @@
+// Copyright (c) 2015 Uber Technologies, Inc.
+
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+// vbumper helps bump version numbers in the repository and in the CHANGELOG.
+package main
+
+import (
+	"bytes"
+	"flag"
+	"html/template"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+var (
+	_changelogFile = flag.String("changelog-file", "CHANGELOG.md", "Filename of the changelog file")
+	_versionFile   = flag.String("version-file", "version.go", "Filename of where the version information is stored")
+	_version       = flag.String("version", "", "Version to mention in changelog and version.go")
+	_versionDate   = flag.String("version-date", "", "Date to use in the changelog, by default the current date")
+	_skipChangelog = flag.Bool("skip-changelog", false, "Skip updating the changelog")
+)
+
+func main() {
+	*_versionDate = time.Now().Format("2006-01-02")
+	flag.Parse()
+
+	if *_version == "" {
+		log.Fatal("Please specify the version to release using --version")
+	}
+	*_version = strings.TrimPrefix(*_version, "v")
+
+	prevVersion, err := updateChanges()
+	if err != nil {
+		log.Fatal("failed to update changelog", err)
+	}
+
+	if err := updateVersion(prevVersion); err != nil {
+		log.Fatal("failed to update version", err)
+	}
+}
+
+func updateVersion(prevVersion string) error {
+	versionBytes, err := ioutil.ReadFile(*_versionFile)
+	if err != nil {
+		return err
+	}
+
+	newContents := insertNewVersion(string(versionBytes), prevVersion, *_version)
+	return ioutil.WriteFile(*_versionFile, []byte(newContents), 0666)
+}
+
+func insertNewVersion(contents, prevVersion, newVersion string) string {
+	// Find the version string in the file
+	versionStart := strings.Index(contents, prevVersion)
+	versionLine := contents[versionStart:]
+	versionEnd := strings.Index(versionLine, `"`) + versionStart
+	return contents[:versionStart] + newVersion + contents[versionEnd:]
+}
+
+func updateChanges() (oldVersion string, _ error) {
+	changelogBytes, err := ioutil.ReadFile(*_changelogFile)
+	if err != nil {
+		return "", err
+	}
+
+	newLog, oldVersion, err := insertNewChangelog(string(changelogBytes))
+	if err != nil {
+		return "", err
+	}
+
+	if *_skipChangelog {
+		return oldVersion, nil
+	}
+
+	return oldVersion, ioutil.WriteFile(*_changelogFile, []byte(newLog), 0666)
+}
+
+func insertNewChangelog(contents string) (string, string, error) {
+	prevVersionHeader := strings.Index(contents, "# ")
+	versionLine := contents[prevVersionHeader:]
+	lastVersionEnd := strings.Index(versionLine, "(")
+	prevVersionTag := strings.TrimSpace(versionLine[1 : lastVersionEnd-1])
+
+	newChanges, err := getNewChangelog(prevVersionTag)
+	if err != nil {
+		return "", "", err
+	}
+
+	// Strip the 'v' prefix.
+	prevVersion := prevVersionTag[1:]
+	newContents := contents[:prevVersionHeader] + newChanges + contents[prevVersionHeader:]
+	return newContents, prevVersion, nil
+}
+
+func getNewChangelog(prevVersion string) (string, error) {
+	changes, err := getChanges(prevVersion)
+	if err != nil {
+		return "", err
+	}
+
+	if len(changes) == 0 {
+		changes = []string{"No changes yet"}
+	}
+
+	buf := &bytes.Buffer{}
+	_changeTmpl.Execute(buf, struct {
+		Version string
+		Date    string
+		Changes []string
+	}{
+		Version: *_version,
+		Date:    *_versionDate,
+		Changes: changes,
+	})
+	return buf.String(), nil
+}
+
+var _changeTmpl = template.Must(template.New("changelog").Parse(
+	`# v{{ .Version }} ({{ .Date }})
+{{ range .Changes }}
+ * {{ . -}}
+{{ end }}
+
+`))
+
+func getChanges(prevVersion string) ([]string, error) {
+	cmd := exec.Command("git", "log", "--oneline", "--no-decorate", prevVersion+"..HEAD")
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+
+	lines := strings.Split(string(out), "\n")
+	newLines := make([]string, 0, len(lines))
+	// Each line is "[commit] [desc]", so ignore everything before the first space.
+	for _, line := range lines {
+		if line == "" {
+			continue
+		}
+		descStart := strings.Index(line, " ")
+		newLines = append(newLines, line[descStart+1:])
+	}
+	return newLines, nil
+}