feat: add Has .gitignore rule

client.go

@@ -14,6 +14,7 @@ type Repo struct {
 	Description   string
 	DefaultBranch string
 	Archived      bool
+	Files         []string // root-level file and directory names
 }
 
 // GitHubClient is the interface for all GitHub API interactions.
@@ -102,8 +103,20 @@ func (c *realGitHubClient) ListRepos(ctx context.Context, org string) ([]Repo, e
 }
 
 func (c *realGitHubClient) ListFiles(ctx context.Context, owner, repo string) ([]string, error) {
-	// TODO: implement when file-existence rules are added
-	return nil, nil
+	url := fmt.Sprintf("https://api.github.com/repos/%s/%s/contents", owner, repo)
+
+	var entries []struct {
+		Name string `json:"name"`
+	}
+	if err := c.doRequest(ctx, url, &entries); err != nil {
+		return nil, fmt.Errorf("list files for %s/%s: %w", owner, repo, err)
+	}
+
+	names := make([]string, len(entries))
+	for i, e := range entries {
+		names[i] = e.Name
+	}
+	return names, nil
 }
 
 func (c *realGitHubClient) CreateIssue(ctx context.Context, owner, repo, title, body string) error {

client_mock_test.go

@@ -6,6 +6,8 @@ import "context"
 type MockGitHubClient struct {
 	Repos    []Repo
 	Err      error
+	Files    map[string][]string // repo name -> file list
+	FilesErr error
 	IssueErr error
 	// CreatedIssue records the last CreateIssue call for assertions.
 	CreatedIssue struct {
@@ -18,6 +20,12 @@ func (m *MockGitHubClient) ListRepos(ctx context.Context, org string) ([]Repo, e
 }
 
 func (m *MockGitHubClient) ListFiles(ctx context.Context, owner, repo string) ([]string, error) {
+	if m.FilesErr != nil {
+		return nil, m.FilesErr
+	}
+	if m.Files != nil {
+		return m.Files[repo], nil
+	}
 	return nil, nil
 }
 

rules.go

@@ -18,6 +18,7 @@ type RuleResult struct {
 func AllRules() []Rule {
 	return []Rule{
 		HasRepoDescription{},
+		HasGitignore{},
 	}
 }
 
@@ -28,3 +29,20 @@ func (r HasRepoDescription) Name() string { return "Has repo description" }
 func (r HasRepoDescription) Check(repo Repo) bool {
 	return strings.TrimSpace(repo.Description) != ""
 }
+
+// HasGitignore checks that a .gitignore file exists in the repo root.
+type HasGitignore struct{}
+
+func (r HasGitignore) Name() string { return "Has .gitignore" }
+func (r HasGitignore) Check(repo Repo) bool {
+	return hasFile(repo.Files, ".gitignore")
+}
+
+func hasFile(files []string, name string) bool {
+	for _, f := range files {
+		if f == name {
+			return true
+		}
+	}
+	return false
+}

rules_test.go

@@ -25,3 +25,27 @@ func TestHasRepoDescription_Fail_WhitespaceOnly(t *testing.T) {
 		t.Errorf("expected fail for repo with whitespace-only description")
 	}
 }
+
+func TestHasGitignore_Pass(t *testing.T) {
+	rule := HasGitignore{}
+
+	if !rule.Check(Repo{Files: []string{"README.md", ".gitignore", "main.go"}}) {
+		t.Error("expected pass when .gitignore exists")
+	}
+}
+
+func TestHasGitignore_Fail(t *testing.T) {
+	rule := HasGitignore{}
+
+	if rule.Check(Repo{Files: []string{"README.md", "main.go"}}) {
+		t.Error("expected fail when .gitignore is missing")
+	}
+}
+
+func TestHasGitignore_Fail_EmptyFiles(t *testing.T) {
+	rule := HasGitignore{}
+
+	if rule.Check(Repo{Files: nil}) {
+		t.Error("expected fail when file list is empty")
+	}
+}

scanner.go

@@ -59,6 +59,12 @@ func Scan(ctx context.Context, client GitHubClient, org string) ([]RepoResult, e
 			continue
 		}
 
+		files, err := client.ListFiles(ctx, org, repo.Name)
+		if err != nil {
+			return nil, fmt.Errorf("list files for repo %s: %w", repo.Name, err)
+		}
+		repo.Files = files
+
 		rr := RepoResult{RepoName: repo.Name}
 		for _, rule := range rules {
 			rr.Results = append(rr.Results, RuleResult{