Do not require changes for docs

Docs-only changes do not require a changelog entry, as we reserve the
changelog for changes to the product. Edit the changelog workflow to
ignore docs-only changes.

bot/internal/bot/changelog.go

@@ -50,6 +50,23 @@ func (b *Bot) CheckChangelog(ctx context.Context) error {
 		return nil
 	}
 
+	files, err := b.c.GitHub.ListFiles(
+		ctx,
+		b.c.Environment.Organization,
+		b.c.Environment.Repository,
+		b.c.Environment.Number,
+	)
+	if err != nil {
+		return trace.Wrap(err, "failed to retrieve pull request files for https://github.com/%s/%s/pull/%d", b.c.Environment.Organization, b.c.Environment.Repository, b.c.Environment.Number)
+
+	}
+
+	c := classifyChanges(b.c, files)
+	if c.Docs && !c.Code {
+		log.Print("PR contains only docs changes. No need for a changelog entry.")
+		return nil
+	}
+
 	changelogEntries := b.getChangelogEntries(pull.UnsafeBody)
 	if len(changelogEntries) == 0 {
 		return trace.BadParameter("Changelog entry not found in the PR body. Please add a %q label to the PR, or changelog lines starting with `%s` followed by the changelog entries for the PR.", NoChangelogLabel, ChangelogPrefix)

bot/internal/bot/changelog_test.go

@@ -39,6 +39,81 @@ func TestChangelog(t *testing.T) {
 	})
 }
 
+func TestMissingNoChangelogLabel(t *testing.T) {
+	tests := []struct {
+		description string
+		files       github.PullRequestFiles
+		expectPass  bool
+	}{
+		{
+			description: "empty file set",
+			files:       github.PullRequestFiles{},
+			expectPass:  false,
+		},
+		{
+			description: "code and docs",
+			files: github.PullRequestFiles{
+				{
+					Name: "lib/service/service.go",
+				},
+				{
+					Name: "docs/pages/index.mdx",
+				},
+			},
+			expectPass: false,
+		},
+		{
+			description: "code only",
+			files: github.PullRequestFiles{
+				{
+					Name: "lib/service/service.go",
+				},
+			},
+			expectPass: false,
+		},
+		{
+			description: "docs only",
+			files: github.PullRequestFiles{
+				{
+					Name: "docs/pages/index.mdx",
+				},
+			},
+			expectPass: true,
+		},
+	}
+
+	for _, c := range tests {
+		t.Run(c.description, func(t *testing.T) {
+			b := &Bot{
+				c: &Config{
+					Environment: &env.Environment{
+						// Assumes the Teleport repository,
+						// where we keep our documentation
+						// content.
+						Organization: "gravitaional",
+						Repository:   "teleport",
+						Number:       0,
+						Author:       "9",
+						UnsafeBase:   "branch/v8",
+						UnsafeHead:   "fix",
+					},
+					GitHub: &fakeGithub{
+						comments: []github.Comment{
+							{
+								Author: "[email protected]",
+								Body:   "PR comment body",
+							},
+						},
+						files: c.files,
+					},
+				},
+			}
+			err := b.CheckChangelog(context.Background())
+			require.Equal(t, c.expectPass, err == nil)
+		})
+	}
+}
+
 func TestGetChangelogEntry(t *testing.T) {
 	tests := []struct {
 		desc     string