Add release note generation tool (elastic#1314)

* no external dependencies
* inspects PRs by version label
* generates structured release notes in asciidoc grouped by type label

operators/hack/release_notes.go

@@ -0,0 +1,266 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"html/template"
+	"io"
+	"net/http"
+	"os"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+const (
+	baseURL             = "https://api.github.com/repos/"
+	repo                = "elastic/cloud-on-k8s/"
+	releaseNoteTemplate = `:issue: https://github.com/{{.Repo}}issues/
+:pull: https://github.com/{{.Repo}}pull/
+
+[[release-notes-{{.Version}}]]
+== {n} version {{.Version}}
+{{range $group, $prs := .Groups}}
+[[{{- id $group -}}-{{$.Version}}]]
+[float]
+=== {{index $.GroupLabels $group}}
+{{range $prs}}
+* {{.Title}} {pull}{{.Number}}[#{{.Number}}]{{with .RelatedIssues -}}
+{{$length := len .}} (issue{{if gt $length 1}}s{{end}}: {{range $idx, $el := .}}{{if $idx}}, {{end}}{issue}{{$el}}[#{{$el}}]{{end}})
+{{- end}}
+{{- end}}
+{{end}}
+`
+)
+
+var (
+	groupLabels = map[string]string{
+		">breaking":    "Breaking changes",
+		">deprecation": "Deprecations",
+		">feature":     "New features",
+		">enhancement": "Enhancements",
+		">bug":         "Bug fixes",
+		"nogroup":      "Misc",
+	}
+
+	ignore = map[string]bool{
+		">non-issue":   true,
+		">refactoring": true,
+		">docs":        true,
+		">test":        true,
+		":ci":          true,
+		"backport":     true,
+	}
+)
+
+// Label models a subset of a GitHub label.
+type Label struct {
+	Name string `json:"name"`
+}
+
+// Issue models a subset of a Github issue.
+type Issue struct {
+	Labels        []Label           `json:"labels"`
+	Body          string            `json:"body"`
+	Title         string            `json:"title"`
+	Number        int               `json:"number"`
+	PullRequest   map[string]string `json:"pull_request,omitempty"`
+	RelatedIssues []int
+}
+
+type GroupedIssues = map[string][]Issue
+
+type TemplateParams struct {
+	Version     string
+	Repo        string
+	GroupLabels map[string]string
+	Groups      GroupedIssues
+}
+
+func fetch(url string, out interface{}) (string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+
+	nextLink := extractNextLink(resp.Header)
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return "", errors.New(fmt.Sprintf("%s: %d %s ", url, resp.StatusCode, resp.Status))
+	}
+
+	if err = json.NewDecoder(resp.Body).Decode(&out); err != nil {
+		return "", err
+	}
+	return nextLink, nil
+}
+
+func extractNextLink(headers http.Header) string {
+	var nextLink string
+	nextRe := regexp.MustCompile(`<([^>]+)>; rel="next"`)
+	links := headers["Link"]
+	for _, lnk := range links {
+		matches := nextRe.FindAllStringSubmatch(lnk, 1)
+		if matches != nil && matches[0][1] != "" {
+			nextLink = matches[0][1]
+			break
+		}
+	}
+	return nextLink
+}
+
+func fetchVersionLabels() ([]string, error) {
+	var versionLabels []string
+	url := fmt.Sprintf("%s%slabels?page=1", baseURL, repo)
+FETCH:
+	var labels []Label
+	next, err := fetch(url, &labels)
+	if err != nil {
+		return nil, err
+	}
+	for _, l := range labels {
+		if strings.HasPrefix(l.Name, "v") {
+			versionLabels = append(versionLabels, l.Name)
+		}
+	}
+	if next != "" {
+		url = next
+		goto FETCH
+	}
+
+	return versionLabels, nil
+}
+
+func fetchIssues(version string) (GroupedIssues, error) {
+	url := fmt.Sprintf("%s%sissues?labels=%s&pagesize=100&state=all&page=1", baseURL, repo, version)
+	var prs []Issue
+FETCH:
+	var tranche []Issue
+	next, err := fetch(url, &tranche)
+	if err != nil {
+		return nil, err
+	}
+	for _, issue := range tranche {
+		// only look at PRs
+		if issue.PullRequest != nil {
+			prs = append(prs, issue)
+		}
+	}
+	if next != "" {
+		url = next
+		goto FETCH
+	}
+	result := make(GroupedIssues)
+	noGroup := "nogroup"
+PR:
+	for _, pr := range prs {
+		prLabels := make(map[string]bool)
+		for _, lbl := range pr.Labels {
+			// remove PRs that have labels to be ignored
+			if ignore[lbl.Name] {
+				continue PR
+			}
+			// build a lookup table of all labels for this PR
+			prLabels[lbl.Name] = true
+		}
+
+		// extract related issues from PR body
+		if err := extractRelatedIssues(&pr); err != nil {
+			return nil, err
+		}
+
+		// group PRs by type label
+		for typeLabel := range groupLabels {
+			if prLabels[typeLabel] {
+				result[typeLabel] = append(result[typeLabel], pr)
+				continue PR
+			}
+		}
+		// or fall back to a default group
+		result[noGroup] = append(result[noGroup], pr)
+	}
+	return result, nil
+}
+
+func extractRelatedIssues(issue *Issue) error {
+	re := regexp.MustCompile(fmt.Sprintf(`https://github.com/%sissues/(\d+)`, repo))
+	matches := re.FindAllStringSubmatch(issue.Body, -1)
+	issues := map[int]struct{}{}
+	for _, capture := range matches {
+		issueNum, err := strconv.Atoi(capture[1])
+		if err != nil {
+			return err
+		}
+		issues[issueNum] = struct{}{}
+
+	}
+	for rel := range issues {
+		issue.RelatedIssues = append(issue.RelatedIssues, rel)
+	}
+	sort.Ints(issue.RelatedIssues)
+	return nil
+}
+
+func dumpIssues(params TemplateParams, out io.Writer) {
+	funcs := template.FuncMap{
+		"id": func(s string) string {
+			return strings.TrimPrefix(s, ">")
+		},
+	}
+	tpl := template.Must(template.New("release_notes").Funcs(funcs).Parse(releaseNoteTemplate))
+	err := tpl.Execute(out, params)
+	if err != nil {
+		println(err)
+	}
+}
+
+func main() {
+	labels, err := fetchVersionLabels()
+	if err != nil {
+		panic(err)
+	}
+
+	if len(os.Args) != 2 {
+		usage(labels)
+	}
+
+	version := os.Args[1]
+	found := false
+	for _, l := range labels {
+		if l == version {
+			found = true
+		}
+	}
+	if !found {
+		usage(labels)
+	}
+
+	groupedIssues, err := fetchIssues(version)
+	if err != nil {
+		panic(err)
+	}
+	dumpIssues(TemplateParams{
+		Version:     strings.TrimPrefix(version, "v"),
+		Repo:        repo,
+		GroupLabels: groupLabels,
+		Groups:      groupedIssues,
+	}, os.Stdout)
+
+}
+
+func usage(labels []string) {
+	println(fmt.Sprintf("USAGE: %s version > outfile", os.Args[0]))
+	println("Known versions:")
+	sort.Strings(labels)
+	for _, l := range labels {
+		println(l)
+	}
+	os.Exit(1)
+}