refactor: improve changelog code

Signed-off-by: Carlos A Becker <caarlos0@users.noreply.github.com>

internal/pipe/changelog/changelog.go

@@ -101,48 +101,66 @@ type changelogGroup struct {
 	order   int
 }
 
-func formatChangelog(ctx *context.Context, entries []string) (string, error) {
-	newLine := "\n"
+func title(s string, level int) string {
+	if s == "" {
+		return ""
+	}
+	return fmt.Sprintf("%s %s", strings.Repeat("#", level), s)
+}
+
+func newLineFor(ctx *context.Context) string {
 	if ctx.TokenType == context.TokenTypeGitLab || ctx.TokenType == context.TokenTypeGitea {
 		// We need two or more whitespace to let markdown interpret
 		// it as newline. See https://docs.gitlab.com/ee/user/markdown.html#newlines for details
 		log.Debug("is gitlab or gitea changelog")
-		newLine = "   \n"
+		return "   \n"
 	}
 
-	if !useChangelog(ctx.Config.Changelog.Use).formatable() {
-		return strings.Join(entries, newLine), nil
-	}
+	return "\n"
+}
 
-	for i := range entries {
-		entry := entries[i]
-		abbr := ctx.Config.Changelog.Abbrev
-		switch abbr {
-		case 0:
-			continue
-		case -1:
-			_, rest, _ := strings.Cut(entry, " ")
-			entries[i] = rest
-		default:
-			commit, rest, _ := strings.Cut(entry, " ")
-			if abbr > len(commit) {
-				continue
-			}
-			entries[i] = fmt.Sprintf("%s %s", commit[:abbr], rest)
+func abbrevEntry(s string, abbr int) string {
+	switch abbr {
+	case 0:
+		return s
+	case -1:
+		_, rest, _ := strings.Cut(s, " ")
+		return rest
+	default:
+		commit, rest, _ := strings.Cut(s, " ")
+		if abbr > len(commit) {
+			return s
 		}
+		return fmt.Sprintf("%s %s", commit[:abbr], rest)
+	}
+}
+
+func abbrev(entries []string, abbr int) []string {
+	result := make([]string, 0, len(entries))
+	for _, entry := range entries {
+		result = append(result, abbrevEntry(entry, abbr))
+	}
+	return result
+}
+
+func formatChangelog(ctx *context.Context, entries []string) (string, error) {
+	if !useChangelog(ctx.Config.Changelog.Use).formatable() {
+		return strings.Join(entries, newLineFor(ctx)), nil
 	}
 
-	result := []string{"## Changelog"}
+	entries = abbrev(entries, ctx.Config.Changelog.Abbrev)
+
+	result := []string{title("Changelog", 2)}
 	if len(ctx.Config.Changelog.Groups) == 0 {
 		log.Debug("not grouping entries")
-		return strings.Join(append(result, filterAndPrefixItems(entries)...), newLine), nil
+		return strings.Join(append(result, filterAndPrefixItems(entries)...), newLineFor(ctx)), nil
 	}
 
 	log.Debug("grouping entries")
 	var groups []changelogGroup
 	for _, group := range ctx.Config.Changelog.Groups {
 		item := changelogGroup{
-			title: group.Title,
+			title: title(group.Title, 3),
 			order: group.Order,
 		}
 		if group.Regexp == "" {
@@ -151,7 +169,7 @@ func formatChangelog(ctx *context.Context, entries []string) (string, error) {
 			// clear array
 			entries = nil
 		} else {
-			regex, err := regexp.Compile(group.Regexp)
+			re, err := regexp.Compile(group.Regexp)
 			if err != nil {
 				return "", fmt.Errorf("failed to group into %q: %w", group.Title, err)
 			}
@@ -159,7 +177,7 @@ func formatChangelog(ctx *context.Context, entries []string) (string, error) {
 			log.Debugf("group: %#v", group)
 			i := 0
 			for _, entry := range entries {
-				match := regex.MatchString(entry)
+				match := re.MatchString(entry)
 				log.Debugf("entry: %s match: %b\n", entry, match)
 				if match {
 					item.entries = append(item.entries, li+entry)
@@ -178,14 +196,20 @@ func formatChangelog(ctx *context.Context, entries []string) (string, error) {
 		}
 	}
 
-	sort.Slice(groups, func(i, j int) bool { return groups[i].order < groups[j].order })
+	sort.Slice(groups, groupSort(groups))
 	for _, group := range groups {
 		if len(group.entries) > 0 {
-			result = append(result, fmt.Sprintf("\n### %s", group.title))
+			result = append(result, group.title)
 			result = append(result, group.entries...)
 		}
 	}
-	return strings.Join(result, newLine), nil
+	return strings.Join(result, newLineFor(ctx)), nil
+}
+
+func groupSort(groups []changelogGroup) func(i, j int) bool {
+	return func(i, j int) bool {
+		return groups[i].order < groups[j].order
+	}
 }
 
 func filterAndPrefixItems(ss []string) []string {

internal/pipe/changelog/changelog_test.go

@@ -817,7 +817,6 @@ func TestChangelogFormat(t *testing.T) {
 				)
 				require.NoError(t, err)
 				require.Equal(t, `## Changelog
-
 ### catch-all
 * aea123 foo
 * aef653 bar`, out)