diff --git a/.golangci.yml b/.golangci.yml
index 34fe368..deed852 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -75,6 +75,9 @@ issues:
     - source: "`json:"
       linters:
         - lll
+    - source: "`yaml:"
+      linters:
+        - lll
 
 run:
   skip-dirs:
diff --git a/build-emacs-for-macos b/build-emacs-for-macos
index 73d7468..59a8fb7 100755
--- a/build-emacs-for-macos
+++ b/build-emacs-for-macos
@@ -53,7 +53,7 @@ class OSVersion
   end
 
   def to_s
-    @to_s ||= "#{major}.#{minor}"
+    @to_s ||= major >= 11 ? major.to_s : "#{major}.#{minor}"
   end
 
   def major
diff --git a/pkg/cask/release_info.go b/pkg/cask/release_info.go
index 35d3ed4..e060613 100644
--- a/pkg/cask/release_info.go
+++ b/pkg/cask/release_info.go
@@ -11,9 +11,11 @@ type ReleaseInfo struct {
 	Assets  map[string]*ReleaseAsset
 }
 
-func (s *ReleaseInfo) Asset(nameMatch string) *ReleaseAsset {
-	if a, ok := s.Assets[nameMatch]; ok {
-		return a
+func (s *ReleaseInfo) Asset(needles ...string) *ReleaseAsset {
+	if len(needles) == 1 {
+		if a, ok := s.Assets[needles[0]]; ok {
+			return a
+		}
 	}
 
 	// Dirty and inefficient way to ensure assets are searched in a predictable
@@ -27,16 +29,20 @@ func (s *ReleaseInfo) Asset(nameMatch string) *ReleaseAsset {
 	})
 
 	for _, a := range assets {
-		if strings.Contains(a.Filename, nameMatch) {
-			return a
+		for _, needle := range needles {
+			if !strings.Contains(a.Filename, needle) {
+				continue
+			}
 		}
+
+		return a
 	}
 
 	return nil
 }
 
-func (s *ReleaseInfo) DownloadURL(nameMatch string) string {
-	a := s.Asset(nameMatch)
+func (s *ReleaseInfo) DownloadURL(needles ...string) string {
+	a := s.Asset(needles...)
 	if a == nil {
 		return ""
 	}
@@ -44,8 +50,8 @@ func (s *ReleaseInfo) DownloadURL(nameMatch string) string {
 	return a.DownloadURL
 }
 
-func (s *ReleaseInfo) SHA256(nameMatch string) string {
-	a := s.Asset(nameMatch)
+func (s *ReleaseInfo) SHA256(needles ...string) string {
+	a := s.Asset(needles...)
 	if a == nil {
 		return ""
 	}
diff --git a/pkg/cli/cask.go b/pkg/cli/cask.go
index dc16b3c..fd47541 100644
--- a/pkg/cli/cask.go
+++ b/pkg/cli/cask.go
@@ -112,7 +112,7 @@ func caskUpdateCmd() *cli2.Command {
 
 func caskUpdateAction(
 	c *cli2.Context,
-	opts *Options,
+	_ *Options,
 	cOpts *caskOptions,
 ) error {
 	updateOpts := &cask.UpdateOptions{
diff --git a/pkg/cli/notarize.go b/pkg/cli/notarize.go
index 1abc44f..794f90d 100644
--- a/pkg/cli/notarize.go
+++ b/pkg/cli/notarize.go
@@ -52,7 +52,7 @@ func notarizeCmd() *cli2.Command {
 	}
 }
 
-func notarizeAction(c *cli2.Context, opts *Options) error {
+func notarizeAction(c *cli2.Context, _ *Options) error {
 	options := &notarize.Options{
 		File:     c.Args().Get(0),
 		BundleID: c.String("bundle-id"),
diff --git a/pkg/cli/plan.go b/pkg/cli/plan.go
index 32df157..cfae4c2 100644
--- a/pkg/cli/plan.go
+++ b/pkg/cli/plan.go
@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 
@@ -37,6 +38,12 @@ func planCmd() *cli2.Command {
 				Name:  "sha",
 				Usage: "override commit SHA of specified git branch/tag",
 			},
+			&cli2.StringFlag{
+				Name:    "format",
+				Aliases: []string{"f"},
+				Usage:   "output format of build plan (yaml or json)",
+				Value:   "yaml",
+			},
 			&cli2.StringFlag{
 				Name: "output",
 				Usage: "output filename to write plan to instead of printing " +
@@ -102,7 +109,18 @@ func planAction(c *cli2.Context, opts *Options) error {
 		return err
 	}
 
-	planYAML, err := p.YAML()
+	format := c.String("format")
+	var plan string
+	switch format {
+	case "yaml", "yml":
+		format = "yaml"
+		plan, err = p.YAML()
+	case "json":
+		format = "json"
+		plan, err = p.JSON()
+	default:
+		err = fmt.Errorf("--format must be yaml or json")
+	}
 	if err != nil {
 		return err
 	}
@@ -111,7 +129,7 @@ func planAction(c *cli2.Context, opts *Options) error {
 	out = os.Stdout
 	if f := c.String("output"); f != "" {
 		logger.Info("writing plan", "file", f)
-		logger.Debug("content", "yaml", planYAML)
+		logger.Debug("content", format, plan)
 		out, err = os.Create(f)
 		if err != nil {
 			return err
@@ -119,7 +137,7 @@ func planAction(c *cli2.Context, opts *Options) error {
 		defer out.Close()
 	}
 
-	_, err = out.WriteString(planYAML)
+	_, err = out.WriteString(plan)
 	if err != nil {
 		return err
 	}
diff --git a/pkg/cli/release.go b/pkg/cli/release.go
index f73c6b5..4de46d8 100644
--- a/pkg/cli/release.go
+++ b/pkg/cli/release.go
@@ -43,7 +43,7 @@ func releaseCmd() *cli2.Command {
 				Usage: "owner/name of GitHub repo to check for release, " +
 					"ignored if a plan is provided",
 				EnvVars: []string{"GITHUB_REPOSITORY"},
-				Value:   "jimeh/emacs-builds",
+				Value:   "",
 			},
 			&cli2.StringFlag{
 				Name:    "name",
@@ -108,7 +108,7 @@ func releaseCheckCmd() *cli2.Command {
 
 func releaseCheckAction(
 	c *cli2.Context,
-	opts *Options,
+	_ *Options,
 	rOpts *releaseOptions,
 ) error {
 	rlsOpts := &release.CheckOptions{
@@ -153,6 +153,12 @@ func releasePublishCmd() *cli2.Command {
 					"specified",
 				Value: "",
 			},
+			&cli2.BoolFlag{
+				Name: "asset-size-check",
+				Usage: "Do not replace existing asset files if local and " +
+					"remote file sizes match.",
+				Value: false,
+			},
 		},
 		Action: releaseActionWrapper(releasePublishAction),
 	}
@@ -160,16 +166,17 @@ func releasePublishCmd() *cli2.Command {
 
 func releasePublishAction(
 	c *cli2.Context,
-	opts *Options,
+	_ *Options,
 	rOpts *releaseOptions,
 ) error {
 	rlsOpts := &release.PublishOptions{
-		Repository:   rOpts.Repository,
-		CommitRef:    c.String("release-sha"),
-		ReleaseName:  rOpts.Name,
-		ReleaseTitle: c.String("title"),
-		AssetFiles:   c.Args().Slice(),
-		GithubToken:  rOpts.GithubToken,
+		Repository:     rOpts.Repository,
+		CommitRef:      c.String("release-sha"),
+		ReleaseName:    rOpts.Name,
+		ReleaseTitle:   c.String("title"),
+		AssetFiles:     c.Args().Slice(),
+		AssetSizeCheck: c.Bool("asset-size-check"),
+		GithubToken:    rOpts.GithubToken,
 	}
 
 	rlsType := c.String("type")
@@ -184,7 +191,13 @@ func releasePublishAction(
 		return fmt.Errorf("invalid --type \"%s\"", rlsType)
 	}
 
+	if c.Args().Len() > 0 {
+		rlsOpts.AssetFiles = c.Args().Slice()
+	}
+
 	if rOpts.Plan != nil {
+		rlsOpts.Source = rOpts.Plan.Source
+
 		if rOpts.Plan.Release != nil {
 			rlsOpts.ReleaseName = rOpts.Plan.Release.Name
 			rlsOpts.ReleaseTitle = rOpts.Plan.Release.Title
@@ -196,7 +209,8 @@ func releasePublishAction(
 			}
 		}
 
-		if rOpts.Plan.Output != nil {
+		// Set asset files based on plan if no file arguments were given.
+		if len(rlsOpts.AssetFiles) == 0 && rOpts.Plan.Output != nil {
 			rlsOpts.AssetFiles = []string{
 				filepath.Join(
 					rOpts.Plan.Output.Directory,
@@ -235,7 +249,7 @@ func releaseBulkCmd() *cli2.Command {
 
 func releaseBulkAction(
 	c *cli2.Context,
-	opts *Options,
+	_ *Options,
 	rOpts *releaseOptions,
 ) error {
 	bulkOpts := &release.BulkOptions{
diff --git a/pkg/commit/commit.go b/pkg/commit/commit.go
index f7d4b79..673386c 100644
--- a/pkg/commit/commit.go
+++ b/pkg/commit/commit.go
@@ -8,11 +8,11 @@ import (
 )
 
 type Commit struct {
-	SHA       string     `yaml:"sha"`
-	Date      *time.Time `yaml:"date"`
-	Author    string     `yaml:"author"`
-	Committer string     `yaml:"committer"`
-	Message   string     `yaml:"message"`
+	SHA       string     `yaml:"sha" json:"sha"`
+	Date      *time.Time `yaml:"date" json:"date"`
+	Author    string     `yaml:"author" json:"author"`
+	Committer string     `yaml:"committer" json:"committer"`
+	Message   string     `yaml:"message" json:"message"`
 }
 
 func New(rc *github.RepositoryCommit) *Commit {
diff --git a/pkg/osinfo/osinfo.go b/pkg/osinfo/osinfo.go
index e8bca96..31d35b8 100644
--- a/pkg/osinfo/osinfo.go
+++ b/pkg/osinfo/osinfo.go
@@ -2,13 +2,14 @@ package osinfo
 
 import (
 	"os/exec"
+	"strconv"
 	"strings"
 )
 
 type OSInfo struct {
-	Name    string `yaml:"name"`
-	Version string `yaml:"version"`
-	Arch    string `yaml:"arch"`
+	Name    string `yaml:"name" json:"name"`
+	Version string `yaml:"version" json:"version"`
+	Arch    string `yaml:"arch" json:"arch"`
 }
 
 func New() (*OSInfo, error) {
@@ -29,8 +30,17 @@ func New() (*OSInfo, error) {
 	}, nil
 }
 
-func (s *OSInfo) MajorMinor() string {
+// DistinctVersion returns macOS version down to a distinct "major"
+// version. For macOS 10.x, this will include the first two numeric parts of the
+// version (10.15), while for 11.x and later, the first numeric part is enough
+// (11).
+func (s *OSInfo) DistinctVersion() string {
 	parts := strings.Split(s.Version, ".")
+
+	if n, _ := strconv.Atoi(parts[0]); n >= 11 {
+		return parts[0]
+	}
+
 	max := len(parts)
 	if max > 2 {
 		max = 2
diff --git a/pkg/plan/create.go b/pkg/plan/create.go
index fbef7eb..d9abe05 100644
--- a/pkg/plan/create.go
+++ b/pkg/plan/create.go
@@ -13,6 +13,7 @@ import (
 	"github.com/jimeh/build-emacs-for-macos/pkg/osinfo"
 	"github.com/jimeh/build-emacs-for-macos/pkg/release"
 	"github.com/jimeh/build-emacs-for-macos/pkg/repository"
+	"github.com/jimeh/build-emacs-for-macos/pkg/source"
 )
 
 var nonAlphaNum = regexp.MustCompile(`[^\w_-]+`)
@@ -76,7 +77,7 @@ func Create(ctx context.Context, opts *Options) (*Plan, error) {
 	buildName := fmt.Sprintf(
 		"Emacs.%s.%s.%s",
 		version,
-		sanitizeString(osInfo.Name+"-"+osInfo.MajorMinor()),
+		sanitizeString(osInfo.Name+"-"+osInfo.DistinctVersion()),
 		sanitizeString(osInfo.Arch),
 	)
 	diskImage := buildName + ".dmg"
@@ -85,11 +86,11 @@ func Create(ctx context.Context, opts *Options) (*Plan, error) {
 		Build: &Build{
 			Name: buildName,
 		},
-		Source: &Source{
+		Source: &source.Source{
 			Ref:        opts.Ref,
 			Repository: repo,
 			Commit:     commitInfo,
-			Tarball: &Tarball{
+			Tarball: &source.Tarball{
 				URL: repo.TarballURL(commitInfo.SHA),
 			},
 		},
diff --git a/pkg/plan/plan.go b/pkg/plan/plan.go
index e33181a..7d119e2 100644
--- a/pkg/plan/plan.go
+++ b/pkg/plan/plan.go
@@ -2,21 +2,21 @@ package plan
 
 import (
 	"bytes"
+	"encoding/json"
 	"io"
 	"os"
 
-	"github.com/jimeh/build-emacs-for-macos/pkg/commit"
 	"github.com/jimeh/build-emacs-for-macos/pkg/osinfo"
-	"github.com/jimeh/build-emacs-for-macos/pkg/repository"
+	"github.com/jimeh/build-emacs-for-macos/pkg/source"
 	"gopkg.in/yaml.v3"
 )
 
 type Plan struct {
-	Build   *Build         `yaml:"build,omitempty"`
-	Source  *Source        `yaml:"source,omitempty"`
-	OS      *osinfo.OSInfo `yaml:"os,omitempty"`
-	Release *Release       `yaml:"release,omitempty"`
-	Output  *Output        `yaml:"output,omitempty"`
+	Build   *Build         `yaml:"build,omitempty" json:"build,omitempty"`
+	Source  *source.Source `yaml:"source,omitempty" json:"source,omitempty"`
+	OS      *osinfo.OSInfo `yaml:"os,omitempty" json:"os,omitempty"`
+	Release *Release       `yaml:"release,omitempty" json:"release,omitempty"`
+	Output  *Output        `yaml:"output,omitempty" json:"output,omitempty"`
 }
 
 // Load attempts to loads a plan YAML from given filename.
@@ -54,29 +54,37 @@ func (s *Plan) YAML() (string, error) {
 	return buf.String(), nil
 }
 
+// WriteJSON writes plan in JSON format to given io.Writer.
+func (s *Plan) WriteJSON(w io.Writer) error {
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+
+	return enc.Encode(s)
+}
+
+// JSON returns plan in JSON format.
+func (s *Plan) JSON() (string, error) {
+	var buf bytes.Buffer
+	err := s.WriteJSON(&buf)
+	if err != nil {
+		return "", err
+	}
+
+	return buf.String(), nil
+}
+
 type Build struct {
-	Name string `yaml:"name,omitempty"`
-}
-
-type Source struct {
-	Ref        string                 `yaml:"ref,omitempty"`
-	Repository *repository.Repository `yaml:"repository,omitempty"`
-	Commit     *commit.Commit         `yaml:"commit,omitempty"`
-	Tarball    *Tarball               `yaml:"tarball,omitempty"`
-}
-
-type Tarball struct {
-	URL string `yaml:"url,omitempty"`
+	Name string `yaml:"name,omitempty" json:"name,omitempty"`
 }
 
 type Release struct {
-	Name       string `yaml:"name"`
-	Title      string `yaml:"title,omitempty"`
-	Draft      bool   `yaml:"draft,omitempty"`
-	Prerelease bool   `yaml:"prerelease,omitempty"`
+	Name       string `yaml:"name" json:"name"`
+	Title      string `yaml:"title,omitempty" json:"title,omitempty"`
+	Draft      bool   `yaml:"draft,omitempty" json:"draft,omitempty"`
+	Prerelease bool   `yaml:"prerelease,omitempty" json:"prerelease,omitempty"`
 }
 
 type Output struct {
-	Directory string `yaml:"directory,omitempty"`
-	DiskImage string `yaml:"disk_image,omitempty"`
+	Directory string `yaml:"directory,omitempty" json:"directory,omitempty"`
+	DiskImage string `yaml:"disk_image,omitempty" json:"disk_image,omitempty"`
 }
diff --git a/pkg/release/publish.go b/pkg/release/publish.go
index d96f675..81ae6fd 100644
--- a/pkg/release/publish.go
+++ b/pkg/release/publish.go
@@ -11,6 +11,7 @@ import (
 	"github.com/hashicorp/go-hclog"
 	"github.com/jimeh/build-emacs-for-macos/pkg/gh"
 	"github.com/jimeh/build-emacs-for-macos/pkg/repository"
+	"github.com/jimeh/build-emacs-for-macos/pkg/source"
 )
 
 type releaseType int
@@ -40,15 +41,26 @@ type PublishOptions struct {
 	// draft)
 	ReleaseType releaseType
 
+	// Source contains the source used to build the asset files. When set a
+	// release body/description text will be generated based on source commit
+	// details.
+	Source *source.Source
+
 	// AssetFiles is a list of files which must all exist in the release for
 	// the check to pass.
 	AssetFiles []string
 
+	// AssetSizeCheck causes a file size check for any existing asset files on a
+	// release which have the same filename as a asset we want to upload. If the
+	// size of the local and remote files are the same, the existing asset file
+	// is left in place. When this is false, given asset files will always be
+	// uploaded, replacing any asset files with the same filename.
+	AssetSizeCheck bool
+
 	// GitHubToken is the OAuth token used to talk to the GitHub API.
 	GithubToken string
 }
 
-//nolint:funlen,gocyclo
 // Publish creates and publishes a GitHub release.
 func Publish(ctx context.Context, opts *PublishOptions) error {
 	logger := hclog.FromContext(ctx).Named("release")
@@ -68,6 +80,16 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 	prerelease := opts.ReleaseType == Prerelease
 	draft := opts.ReleaseType == Draft
 
+	body := ""
+	if opts.Source != nil {
+		body, err = releaseBody(opts)
+		if err != nil {
+			return err
+		}
+		logger.Debug("rendered release body", "content", body)
+	}
+
+	created := false
 	logger.Info("checking release", "tag", tagName)
 	release, resp, err := gh.Repositories.GetReleaseByTag(
 		ctx, opts.Repository.Owner(), opts.Repository.Name(), tagName,
@@ -77,6 +99,7 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 			return err
 		}
 
+		created = true
 		logger.Info("creating release", "tag", tagName, "name", name)
 
 		release, _, err = gh.Repositories.CreateRelease(
@@ -87,6 +110,7 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 				TargetCommitish: &opts.CommitRef,
 				Prerelease:      boolPtr(false),
 				Draft:           boolPtr(true),
+				Body:            &body,
 			},
 		)
 		if err != nil {
@@ -94,62 +118,9 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 		}
 	}
 
-	for _, fileName := range files {
-		fileIO, err2 := os.Open(fileName)
-		if err2 != nil {
-			return err2
-		}
-		defer fileIO.Close()
-
-		fileInfo, err2 := fileIO.Stat()
-		if err2 != nil {
-			return err2
-		}
-
-		fileBaseName := filepath.Base(fileName)
-		assetExists := false
-
-		for _, a := range release.Assets {
-			if a.GetName() != fileBaseName {
-				continue
-			}
-
-			if a.GetSize() == int(fileInfo.Size()) {
-				logger.Info("asset exists with correct size",
-					"file", fileBaseName,
-					"local_size", byteCountIEC(fileInfo.Size()),
-					"remote_size", byteCountIEC(int64(a.GetSize())),
-				)
-				assetExists = true
-			} else {
-				_, err = gh.Repositories.DeleteReleaseAsset(
-					ctx, opts.Repository.Owner(), opts.Repository.Name(),
-					a.GetID(),
-				)
-				if err != nil {
-					return err
-				}
-				logger.Info(
-					"deleted asset with wrong size", "file", fileBaseName,
-				)
-			}
-		}
-
-		if !assetExists {
-			logger.Info("uploading asset",
-				"file", fileBaseName,
-				"size", byteCountIEC(fileInfo.Size()),
-			)
-			_, _, err2 = gh.Repositories.UploadReleaseAsset(
-				ctx, opts.Repository.Owner(), opts.Repository.Name(),
-				release.GetID(),
-				&github.UploadOptions{Name: fileBaseName},
-				fileIO,
-			)
-			if err2 != nil {
-				return err2
-			}
-		}
+	err = uploadReleaseAssets(ctx, gh, release, files, opts)
+	if err != nil {
+		return err
 	}
 
 	changed := false
@@ -158,6 +129,11 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 		changed = true
 	}
 
+	if body != "" && release.GetBody() != body {
+		release.Body = &body
+		changed = true
+	}
+
 	if release.GetDraft() != draft {
 		release.Draft = &draft
 		changed = true
@@ -169,6 +145,7 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 	}
 
 	if changed {
+		logger.Info("updating release attributes", "url", release.GetHTMLURL())
 		release, _, err = gh.Repositories.EditRelease(
 			ctx, opts.Repository.Owner(), opts.Repository.Name(),
 			release.GetID(), release,
@@ -178,13 +155,89 @@ func Publish(ctx context.Context, opts *PublishOptions) error {
 		}
 	}
 
-	logger.Info("release created", "url", release.GetHTMLURL())
+	if created {
+		logger.Info("release created", "url", release.GetHTMLURL())
+	} else {
+		logger.Info("release updated", "url", release.GetHTMLURL())
+	}
+
+	return nil
+}
+
+func uploadReleaseAssets(
+	ctx context.Context,
+	gh *github.Client,
+	release *github.RepositoryRelease,
+	fileNames []string,
+	opts *PublishOptions,
+) error {
+	logger := hclog.FromContext(ctx).Named("release")
+
+	for _, fileName := range fileNames {
+		logger.Debug("processing asset", "file", filepath.Base(fileName))
+
+		fileIO, err := os.Open(fileName)
+		if err != nil {
+			return err
+		}
+		defer fileIO.Close()
+
+		fileInfo, err := fileIO.Stat()
+		if err != nil {
+			return err
+		}
+
+		fileBaseName := filepath.Base(fileName)
+		assetExists := false
+
+		for _, a := range release.Assets {
+			if a.GetName() != fileBaseName {
+				continue
+			}
+
+			if opts.AssetSizeCheck && a.GetSize() == int(fileInfo.Size()) {
+				logger.Info("asset exists with correct size",
+					"file", fileBaseName,
+					"local_size", byteCountIEC(fileInfo.Size()),
+					"remote_size", byteCountIEC(int64(a.GetSize())),
+				)
+				assetExists = true
+			} else {
+				logger.Info(
+					"deleting existing asset", "file", fileBaseName,
+				)
+				_, err = gh.Repositories.DeleteReleaseAsset(
+					ctx, opts.Repository.Owner(), opts.Repository.Name(),
+					a.GetID(),
+				)
+				if err != nil {
+					return err
+				}
+			}
+		}
+
+		if !assetExists {
+			logger.Info("uploading asset",
+				"file", fileBaseName,
+				"size", byteCountIEC(fileInfo.Size()),
+			)
+			_, _, err = gh.Repositories.UploadReleaseAsset(
+				ctx, opts.Repository.Owner(), opts.Repository.Name(),
+				release.GetID(),
+				&github.UploadOptions{Name: fileBaseName},
+				fileIO,
+			)
+			if err != nil {
+				return err
+			}
+		}
+	}
 
 	return nil
 }
 
 func publishFileList(files []string) ([]string, error) {
-	var output []string
+	results := map[string]struct{}{}
 	for _, file := range files {
 		var err error
 		file, err = filepath.Abs(file)
@@ -200,11 +253,10 @@ func publishFileList(files []string) ([]string, error) {
 			return nil, fmt.Errorf("\"%s\" is not a file", file)
 		}
 
-		output = append(output, file)
+		results[file] = struct{}{}
 		sumFile := file + ".sha256"
 
 		_, err = os.Stat(sumFile)
-		fmt.Printf("err: %+v\n", err)
 		if err != nil {
 			if os.IsNotExist(err) {
 				continue
@@ -212,7 +264,12 @@ func publishFileList(files []string) ([]string, error) {
 
 			return nil, err
 		}
-		output = append(output, sumFile)
+		results[sumFile] = struct{}{}
+	}
+
+	var output []string
+	for f := range results {
+		output = append(output, f)
 	}
 
 	return output, nil
diff --git a/pkg/release/release_body.go b/pkg/release/release_body.go
new file mode 100644
index 0000000..b014075
--- /dev/null
+++ b/pkg/release/release_body.go
@@ -0,0 +1,80 @@
+package release
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"text/template"
+)
+
+var tplFuncs = template.FuncMap{
+	"indent": func(n int, s string) string {
+		pad := strings.Repeat(" ", n)
+
+		return pad + strings.ReplaceAll(s, "\n", "\n"+pad)
+	},
+}
+
+var bodyTpl = template.Must(template.New("body").Funcs(tplFuncs).Parse(`
+{{- $t := "` + "`" + `" -}}
+### Build Details
+
+{{ with .SourceURL -}}
+- Source: {{ . }}
+{{- end }}
+{{- if and .CommitSHA .CommitURL }}
+- Commit: [{{ $t }}{{ .CommitSHA }}{{ $t }}]
+  {{- if .CommitURL }}({{ .CommitURL }}){{ end }}
+{{- else if and .CommitSHA }}
+- Commit: {{ $t }}{{ .CommitSHA }}{{ $t }}
+{{- end }}
+{{- with .TarballURL }}
+- Tarball: {{ . }}
+{{- end }}
+{{- with .BuildLogURL }}
+- Build Log: {{ . }} (available for 90 days)
+{{- end }}`,
+))
+
+type bodyData struct {
+	SourceURL   string
+	CommitSHA   string
+	CommitURL   string
+	BuildLogURL string
+	TarballURL  string
+}
+
+func releaseBody(opts *PublishOptions) (string, error) {
+	src := opts.Source
+
+	if src.Repository == nil || src.Commit == nil {
+		return "", nil
+	}
+
+	data := &bodyData{
+		SourceURL:  src.Repository.TreeURL(src.Ref),
+		CommitSHA:  src.Commit.SHA,
+		CommitURL:  src.Repository.CommitURL(src.Commit.SHA),
+		TarballURL: src.Repository.TarballURL(src.Commit.SHA),
+	}
+
+	// If available, use the exact value from the build plan.
+	if src.Tarball != nil {
+		data.TarballURL = src.Tarball.URL
+	}
+
+	// If running within GitHub Actions, provide link to build log.
+	if opts.Repository != nil {
+		if id := os.Getenv("GITHUB_RUN_ID"); id != "" {
+			data.BuildLogURL = opts.Repository.ActionRunURL(id)
+		}
+	}
+
+	var buf bytes.Buffer
+	err := bodyTpl.Execute(&buf, data)
+	if err != nil {
+		return "", err
+	}
+
+	return buf.String(), nil
+}
diff --git a/pkg/repository/repository.go b/pkg/repository/repository.go
index 98d5eeb..501fa28 100644
--- a/pkg/repository/repository.go
+++ b/pkg/repository/repository.go
@@ -22,8 +22,8 @@ const GitHub Type = "github"
 // Repository represents basic information about a repository with helper
 // methods to get various pieces of information from it.
 type Repository struct {
-	Type   Type   `yaml:"type,omitempty"`
-	Source string `yaml:"source,omitempty"`
+	Type   Type   `yaml:"type,omitempty" json:"type,omitempty"`
+	Source string `yaml:"source,omitempty" json:"source,omitempty"`
 }
 
 func NewGitHub(ownerAndName string) (*Repository, error) {
@@ -89,3 +89,42 @@ func (s *Repository) TarballURL(ref string) string {
 		return ""
 	}
 }
+
+func (s *Repository) CommitURL(ref string) string {
+	if ref == "" {
+		return ""
+	}
+
+	switch s.Type {
+	case GitHub:
+		return GitHubBaseURL + s.Source + "/commit/" + ref
+	default:
+		return ""
+	}
+}
+
+func (s *Repository) TreeURL(ref string) string {
+	if ref == "" {
+		return ""
+	}
+
+	switch s.Type {
+	case GitHub:
+		return GitHubBaseURL + s.Source + "/tree/" + ref
+	default:
+		return ""
+	}
+}
+
+func (s *Repository) ActionRunURL(runID string) string {
+	if runID == "" {
+		return ""
+	}
+
+	switch s.Type {
+	case GitHub:
+		return GitHubBaseURL + s.Source + "/actions/runs/" + runID
+	default:
+		return ""
+	}
+}
diff --git a/pkg/source/source.go b/pkg/source/source.go
new file mode 100644
index 0000000..b315168
--- /dev/null
+++ b/pkg/source/source.go
@@ -0,0 +1,17 @@
+package source
+
+import (
+	"github.com/jimeh/build-emacs-for-macos/pkg/commit"
+	"github.com/jimeh/build-emacs-for-macos/pkg/repository"
+)
+
+type Source struct {
+	Ref        string                 `yaml:"ref,omitempty" json:"ref,omitempty"`
+	Repository *repository.Repository `yaml:"repository,omitempty" json:"repository,omitempty"`
+	Commit     *commit.Commit         `yaml:"commit,omitempty" json:"commit,omitempty"`
+	Tarball    *Tarball               `yaml:"tarball,omitempty" json:"tarball,omitempty"`
+}
+
+type Tarball struct {
+	URL string `yaml:"url,omitempty" json:"url,omitempty"`
+}