generate release notes for delta since latest release of each chart

README.md

@@ -258,7 +258,7 @@ git-upload-url: https://uploads.github.com/
 cr upload --config config.yaml
 ```
 
-`cr` supports any format [Viper](https://github.com/spf13/viper) can read, i. e. JSON, TOML, YAML, HCL, and Java properties files.
+`cr` supports any format [Viper](https://github.com/spf13/viper) can read, i.e. JSON, TOML, YAML, HCL, and Java properties files.
 
 Notice that if no config file is specified, `cr.yaml` (or any of the supported formats) is loaded from the current directory, `$HOME/.cr`, or `/etc/cr`, in that order, if found.
 
@@ -279,7 +279,7 @@ and then look for `upload_url`. You need the part of the URL that appears before
 
 ## Common Error Messages
 
-During the upload, you can get the follwing error :
+During the upload, you can get the following error :
 
 ```bash
 422 Validation Failed [{Resource:Release Field:tag_name Code:already_exists Message:}]
@@ -289,8 +289,8 @@ You can solve it by adding the `--skip-existing` flag to your command. More deta
 
 ## Known Bug
 
-Currently, if you set the upload URL incorrectly, let's say to something like `https://example.com/uploads/`, then `cr upload` will appear to work, but the release will not be complete. When everything is working there should be 3 assets in each release, but instead there will only be the 2 source code assets. The third asset, which is what helm actually uses, is missing. This issue will become apparent when you run `cr index` and it always claims that nothing has changed, because it can't find the asset it expects for the release.
+Currently, if you set the upload URL incorrectly, let's say to something like `https://example.com/uploads/`, then `cr upload` will appear to work, but the release will not be complete. When everything is working there should be three assets in each release, but instead, there will only be two source code assets. The third asset is missing and is needed by Helm. This issue will become apparent when you run `cr index` and it always claims that nothing has changed, because it can't find the asset it expects for the release.
 
-It appears like the [go-github Do call](https://github.com/google/go-github/blob/master/github/github.go#L520) does not catch the fact that the upload URL is incorrect and pass back the expected error. If the asset upload fails, it would be better if the release was rolled back (deleted) and an appropriate log message is be displayed to the user.
+It appears like the [go-github Do call](https://github.com/google/go-github/blob/master/github/github.go#L520) does not catch the fact that the upload URL is incorrect and passes back the expected error. If the asset upload fails, it would be better if the release was rolled back (deleted) and an appropriate log message is displayed to the user.
 
 The `cr index` command should also generate a warning when a release has no assets attached to it, to help people detect and troubleshoot this type of problem.

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

@@ -37,6 +37,8 @@ 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

@@ -25,6 +25,7 @@ import (
 	"github.com/Songmu/retry"
 	"github.com/pkg/errors"
 
+	"github.com/blang/semver"
 	"github.com/google/go-github/v56/github"
 	"golang.org/x/oauth2"
 )
@@ -34,7 +35,6 @@ type Release struct {
 	Description          string
 	Assets               []*Asset
 	Commit               string
-	GenerateReleaseNotes bool
 	MakeLatest           string
 }
 
@@ -102,14 +102,72 @@ 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) {
+	// Find all releases with tags matching prefix
+	opt := &github.ListOptions{
+		PerPage: 100,
+	}
+	var releases []*github.RepositoryRelease
+	for {
+		rels, resp, err := c.Repositories.ListReleases(context.TODO(), c.owner, c.repo, opt)
+		if err != nil {
+			return nil, err
+		}
+		for _, rel := range rels {
+			if strings.HasPrefix(*rel.TagName, prefix) {
+				releases = append(releases, rel)
+			}
+		}
+		if resp.NextPage == 0 {
+			break
+		}
+		opt.Page = resp.NextPage
+	}
+
+	// Sort those tags by their semver suffixes
+	var tags []semver.Version
+	for _, rel := range releases {
+		tags = append(tags, semver.MustParse(*rel.TagName))
+	}
+
+	// Find release with highest semver tag
+	semver.Sort(tags)
+	latestTag := tags[len(tags)-1]
+	var release *github.RepositoryRelease
+	if rel, _, err := c.Repositories.GetReleaseByTag(context.TODO(), c.owner, c.repo, prefix+latestTag.String()); err == nil {
+		release = rel
+	}
+
+	result := &Release{
+		Assets: []*Asset{},
+	}
+	for _, ass := range release.Assets {
+		asset := &Asset{*ass.Name, *ass.BrowserDownloadURL}
+		result.Assets = append(result.Assets, asset)
+	}
+	return result, nil
+}
+
+// GenerateReleaseNotes generates the release notes for a release
+func (c *Client) GenerateReleaseNotes(_ context.Context, latestRelease *Release, nextRelease string) (string, error) {
+	notes, _, err := c.Repositories.GenerateReleaseNotes(context.TODO(), c.owner, c.repo, &github.GenerateNotesOptions{
+		TagName:         nextRelease,
+		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,
 	}
 

pkg/releaser/releaser.go

@@ -50,6 +50,8 @@ 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, nextRelease string) (string, error)
 }
 
 type Git interface {
@@ -238,16 +240,27 @@ 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)
 			}
 		}
 		fmt.Printf("The release note file %q, is not present in the chart package\n", r.config.ReleaseNotesFile)
+	} else 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)
+		}
+		notes, err := r.github.GenerateReleaseNotes(context.TODO(), latestRelease, chart.Metadata.Version)
+		if err != nil {
+			return "", errors.Wrapf(err, "failed to generate release notes for chart %s", chart.Metadata.Name)
+		}
+		return notes, nil
+	} else {
+		return chart.Metadata.Description, nil
 	}
-	return chart.Metadata.Description
 }
 
 func (r *Releaser) splitPackageNameAndVersion(pkg string) []string {
@@ -307,15 +320,18 @@ 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),
 		}
 		provFile := fmt.Sprintf("%s.prov", p)