feat: add Has LICENSE rule

rules.go

@@ -20,6 +20,7 @@ func AllRules() []Rule {
 		HasRepoDescription{},
 		HasGitignore{},
 		HasSubstantialReadme{},
+		HasLicense{},
 	}
 }
 
@@ -48,6 +49,14 @@ func (r HasSubstantialReadme) Check(repo Repo) bool {
 	return ok && f.Size > 2048
 }
 
+// HasLicense checks that a LICENSE or LICENSE.md file exists in the repo root.
+type HasLicense struct{}
+
+func (r HasLicense) Name() string { return "Has LICENSE" }
+func (r HasLicense) Check(repo Repo) bool {
+	return hasFile(repo.Files, "LICENSE") || hasFile(repo.Files, "LICENSE.md")
+}
+
 func findFile(files []FileEntry, name string) (FileEntry, bool) {
 	for _, f := range files {
 		if f.Name == name {

rules_test.go

@@ -73,3 +73,27 @@ func TestHasSubstantialReadme_Fail_Missing(t *testing.T) {
 		t.Error("expected fail when README.md is missing")
 	}
 }
+
+func TestHasLicense_Pass_LICENSE(t *testing.T) {
+	rule := HasLicense{}
+
+	if !rule.Check(Repo{Files: []FileEntry{{Name: "LICENSE"}}}) {
+		t.Error("expected pass when LICENSE exists")
+	}
+}
+
+func TestHasLicense_Pass_LICENSEmd(t *testing.T) {
+	rule := HasLicense{}
+
+	if !rule.Check(Repo{Files: []FileEntry{{Name: "LICENSE.md"}}}) {
+		t.Error("expected pass when LICENSE.md exists")
+	}
+}
+
+func TestHasLicense_Fail(t *testing.T) {
+	rule := HasLicense{}
+
+	if rule.Check(Repo{Files: []FileEntry{{Name: "README.md"}}}) {
+		t.Error("expected fail when no LICENSE file exists")
+	}
+}