[DOC] Suppress documentation for internals

Author: nobu

.github/workflows/test.yml

@@ -33,4 +33,4 @@ jobs:
       run: bundle exec rake test
     - name: RDoc coverage
       run: |
-        rdoc -C .
+        rdoc -C --visibility=private .

lib/erb/compiler.rb

@@ -480,7 +480,6 @@ def initialize from
     end
   }.new(caller(0)).c
   private_constant :WARNING_UPLEVEL
-  # :startdoc:
 
   def warn_invalid_trim_mode(mode, uplevel:)
     warn "Invalid ERB trim mode: #{mode.inspect} (trim_mode: nil, 0, 1, 2, or String composed of '%' and/or '-', '>', '<>')", uplevel: uplevel + WARNING_UPLEVEL

lib/erb/util.rb

@@ -19,6 +19,7 @@
   # A subset of ERB::Util. Unlike ERB::Util#html_escape, we expect/hope
   # Rails will not monkey-patch ERB::Escape#html_escape.
   module ERB::Escape
+    # :stopdoc:
     def html_escape(s)
       CGI.escapeHTML(s.to_s)
     end