generate release notes for delta since latest release of each chart

Signed-off-by: Kenneth Bingham <kenneth.bingham@netfoundry.io>

go.mod

@@ -7,6 +7,7 @@ toolchain go1.22.4
 require (
 	github.com/MakeNowJust/heredoc v1.0.0
 	github.com/Songmu/retry v0.1.0
+	github.com/blang/semver v3.5.1+incompatible
 	github.com/google/go-github/v56 v56.0.0
 	github.com/magefile/mage v1.15.0
 	github.com/mitchellh/go-homedir v1.1.0

go.sum

@@ -38,6 +38,8 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/blang/semver v3.5.1+incompatible h1:cQNTCjp13qL8KC3Nbxr/y2Bqb63oX6wdnnjpJbkM4JQ=
+github.com/blang/semver v3.5.1+incompatible/go.mod h1:kRBLl5iJ+tD4TcOOxsy/0fnwebNt5EWlYSAyrTnjyyk=
 github.com/blang/semver/v4 v4.0.0 h1:1PFHFE6yCCTv8C1TeyNNarDzntLi7wMI5i/pzqYIsAM=
 github.com/blang/semver/v4 v4.0.0/go.mod h1:IbckMUScFkM3pff0VJDNKRiT6TG/YpiHIM2yvyW5YoQ=
 github.com/bshuster-repo/logrus-logstash-hook v1.0.0 h1:e+C0SB5R1pu//O4MQ3f9cFuPGoOVeF2fE4Og9otCc70=

pkg/github/github.go

@@ -24,18 +24,20 @@ import (
 
 	"github.com/Songmu/retry"
 	"github.com/pkg/errors"
+	"helm.sh/helm/v3/pkg/chart"
 
+	"github.com/blang/semver"
 	"github.com/google/go-github/v56/github"
 	"golang.org/x/oauth2"
 )
 
 type Release struct {
-	Name                 string
-	Description          string
-	Assets               []*Asset
-	Commit               string
-	GenerateReleaseNotes bool
-	MakeLatest           string
+	Name        string
+	Description string
+	Assets      []*Asset
+	Commit      string
+	MakeLatest  string
+	SemVer      semver.Version
 }
 
 type Asset struct {
@@ -102,15 +104,73 @@ func (c *Client) GetRelease(_ context.Context, tag string) (*Release, error) {
 	return result, nil
 }
 
+// GetLatestChartRelease queries the GitHub API for the previous release of a chart
+func (c *Client) GetLatestChartRelease(_ context.Context, prefix string) (*Release, error) {
+	// Append hyphen to prefix unless already present
+	prefix = strings.TrimSuffix(prefix, "-") + "-"
+
+	// Find all versions with tags matching prefix
+	opt := &github.ListOptions{
+		PerPage: 100,
+	}
+	var versions []semver.Version
+	for {
+		rels, resp, err := c.Repositories.ListReleases(context.TODO(), c.owner, c.repo, opt)
+		if err != nil {
+			return nil, err
+		} else if len(rels) == 0 {
+			return nil, errors.New("no releases found")
+		}
+		for _, rel := range rels {
+			if strings.HasPrefix(*rel.TagName, prefix) {
+				version := semver.MustParse(strings.TrimPrefix(*rel.TagName, prefix))
+				versions = append(versions, version)
+			}
+		}
+		if resp.NextPage == 0 {
+			break
+		}
+		opt.Page = resp.NextPage
+	}
+
+	// Sort versions ascending
+	semver.Sort(versions)
+
+	// Find highest version
+	latestVersion := versions[len(versions)-1]
+	var release *github.RepositoryRelease
+	if rel, _, err := c.Repositories.GetReleaseByTag(context.TODO(), c.owner, c.repo, prefix+latestVersion.String()); err == nil {
+		release = rel
+	}
+
+	result := &Release{
+		Name:   *release.TagName,
+		Commit: *release.TargetCommitish,
+		SemVer: latestVersion,
+	}
+	return result, nil
+}
+
+// GenerateReleaseNotes generates the release notes for a release
+func (c *Client) GenerateReleaseNotes(_ context.Context, latestRelease *Release, chart *chart.Chart) (string, error) {
+	notes, _, err := c.Repositories.GenerateReleaseNotes(context.TODO(), c.owner, c.repo, &github.GenerateNotesOptions{
+		TagName:         chart.Metadata.Name + "-" + chart.Metadata.Version,
+		PreviousTagName: &latestRelease.Name,
+	})
+	if err != nil {
+		return "", err
+	}
+	return notes.Body, err
+}
+
 // CreateRelease creates a new release object in the GitHub API
 func (c *Client) CreateRelease(_ context.Context, input *Release) error {
 	req := &github.RepositoryRelease{
-		Name:                 &input.Name,
-		Body:                 &input.Description,
-		TagName:              &input.Name,
-		TargetCommitish:      &input.Commit,
-		GenerateReleaseNotes: &input.GenerateReleaseNotes,
-		MakeLatest:           &input.MakeLatest,
+		Name:            &input.Name,
+		Body:            &input.Description,
+		TagName:         &input.Name,
+		TargetCommitish: &input.Commit,
+		MakeLatest:      &input.MakeLatest,
 	}
 
 	release, _, err := c.Repositories.CreateRelease(context.TODO(), c.owner, c.repo, req)

pkg/releaser/releaser.go

@@ -28,6 +28,7 @@ import (
 	"time"
 
 	"github.com/Songmu/retry"
+	"github.com/blang/semver"
 
 	"text/template"
 
@@ -50,6 +51,8 @@ type GitHub interface {
 	CreateRelease(ctx context.Context, input *github.Release) error
 	GetRelease(ctx context.Context, tag string) (*github.Release, error)
 	CreatePullRequest(owner string, repo string, message string, head string, base string) (string, error)
+	GetLatestChartRelease(ctx context.Context, prefix string) (*github.Release, error)
+	GenerateReleaseNotes(ctx context.Context, latestRelease *github.Release, chart *chart.Chart) (string, error)
 }
 
 type Git interface {
@@ -238,16 +241,52 @@ func (r *Releaser) computeReleaseName(chart *chart.Chart) (string, error) {
 	return releaseName, nil
 }
 
-func (r *Releaser) getReleaseNotes(chart *chart.Chart) string {
+func (r *Releaser) getReleaseNotes(chart *chart.Chart) (string, error) {
 	if r.config.ReleaseNotesFile != "" {
 		for _, f := range chart.Files {
 			if f.Name == r.config.ReleaseNotesFile {
-				return string(f.Data)
+				return string(f.Data), nil
 			}
 		}
 		fmt.Printf("The release note file %q, is not present in the chart package\n", r.config.ReleaseNotesFile)
 	}
-	return chart.Metadata.Description
+	if r.config.GenerateReleaseNotes {
+		latestRelease, err := r.github.GetLatestChartRelease(context.TODO(), chart.Metadata.Name)
+		if err != nil {
+			return "", errors.Wrapf(err, "failed to get latest release for chart %s", chart.Metadata.Name)
+		}
+		nextVersion := semver.MustParse(chart.Metadata.Version)
+		versions := []semver.Version{nextVersion, latestRelease.SemVer}
+		semver.Sort(versions)
+		highest := versions[len(versions)-1]
+		// skip generating notes if there's already a higher version in GitHub
+		if nextVersion.String() == highest.String() {
+			notes, err := r.github.GenerateReleaseNotes(context.TODO(), latestRelease, chart)
+			if err != nil {
+				return "", errors.Wrapf(err, "failed to generate release notes for chart %s", chart.Metadata.Name)
+			}
+			return notes, nil
+		}
+	}
+	if r.config.GenerateReleaseNotes {
+		latestRelease, err := r.github.GetLatestChartRelease(context.TODO(), chart.Metadata.Name)
+		if err != nil {
+			return "", errors.Wrapf(err, "failed to get latest release for chart %s", chart.Metadata.Name)
+		}
+		nextVersion := semver.MustParse(chart.Metadata.Version)
+		versions := []semver.Version{nextVersion, latestRelease.SemVer}
+		semver.Sort(versions)
+		highest := versions[len(versions)-1]
+		// skip generating notes if there's already a higher version in GitHub
+		if nextVersion.String() == highest.String() {
+			notes, err := r.github.GenerateReleaseNotes(context.TODO(), latestRelease, chart)
+			if err != nil {
+				return "", errors.Wrapf(err, "failed to generate release notes for chart %s", chart.Metadata.Name)
+			}
+			return notes, nil
+		}
+	}
+	return chart.Metadata.Description, nil
 }
 
 func (r *Releaser) splitPackageNameAndVersion(pkg string) []string {
@@ -307,16 +346,19 @@ func (r *Releaser) CreateReleases() error {
 		if err != nil {
 			return err
 		}
+		notes, err := r.getReleaseNotes(ch)
+		if err != nil {
+			return err
+		}
 
 		release := &github.Release{
 			Name:        releaseName,
-			Description: r.getReleaseNotes(ch),
+			Description: notes,
 			Assets: []*github.Asset{
 				{Path: p},
 			},
-			Commit:               r.config.Commit,
-			GenerateReleaseNotes: r.config.GenerateReleaseNotes,
-			MakeLatest:           strconv.FormatBool(r.config.MakeReleaseLatest),
+			Commit:     r.config.Commit,
+			MakeLatest: strconv.FormatBool(r.config.MakeReleaseLatest),
 		}
 		provFile := fmt.Sprintf("%s.prov", p)
 		if _, err := os.Stat(provFile); err == nil {

pkg/releaser/releaser_test.go

@@ -21,13 +21,15 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/blang/semver"
 	"github.com/helm/chart-releaser/pkg/github"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"helm.sh/helm/v3/pkg/provenance"
 	"helm.sh/helm/v3/pkg/repo"
 
 	"github.com/helm/chart-releaser/pkg/config"
+	"helm.sh/helm/v3/pkg/chart"
 )
 
 type FakeGitHub struct {
@@ -115,6 +117,31 @@ func (f *FakeGitHub) CreatePullRequest(owner string, repo string, message string
 	return "https://github.com/owner/repo/pull/42", nil
 }
 
+// GetLatestChartRelease queries the GitHub API for the previous release of a chart
+func (f *FakeGitHub) GetLatestChartRelease(_ context.Context, prefix string) (*github.Release, error) {
+	f.Called(prefix)
+
+	result := &github.Release{
+		Name:   prefix + "-1.2.3",
+		Commit: "c11eea26f51782a8063ded1085384acb2928fd91",
+		SemVer: semver.Version{
+			Major: 1,
+			Minor: 2,
+			Patch: 3,
+		},
+	}
+	return result, nil
+}
+
+// GenerateReleaseNotes generates the release notes for a release
+func (f *FakeGitHub) GenerateReleaseNotes(_ context.Context, latestRelease *github.Release, chart *chart.Chart) (string, error) {
+	f.Called(latestRelease, chart)
+
+	notes := "# Noted."
+
+	return notes, nil
+}
+
 func TestReleaser_UpdateIndexFile(t *testing.T) {
 	indexDir, _ := os.MkdirTemp(".", "index")
 	defer os.RemoveAll(indexDir)