Fix a heading identification bug

m/textstyles/manPageHeading.go

@@ -62,7 +62,7 @@ func isManPageHeading(s string) bool {
 		}
 	}
 
-	return true
+	return nextCharNumber%3 == 0
 }
 
 // Alphabetic chars must be upper case, all others are fine.

m/textstyles/manPageHeading_test.go

@@ -0,0 +1,20 @@
+package textstyles
+
+import (
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func TestIsManPageHeading(t *testing.T) {
+	assert.Assert(t, !isManPageHeading(""))
+	assert.Assert(t, !isManPageHeading("A"), "Incomplete sequence")
+	assert.Assert(t, !isManPageHeading("A\b"), "Incomplete sequence")
+
+	assert.Assert(t, isManPageHeading("A\bA"))
+
+	assert.Assert(t, !isManPageHeading("A\bC"), "Different first and last char")
+	assert.Assert(t, !isManPageHeading("a\ba"), "Not ALL CAPS")
+
+	assert.Assert(t, !isManPageHeading("A\bAX"), "Incomplete sequence")
+}