Remove example filepaths from code blocks in guides

Some code examples use commented out paths for the path where the code
should be written to. These paths can be ignored in the clipboard when
using the "copy" button.

Co-authored-by: Carlos Antonio da Silva <carlosantoniodasilva@gmail.com>

guides/rails_guides/markdown/renderer.rb

@@ -8,6 +8,10 @@ Rouge::Lexers::Shell::BUILTINS << "|bin/rails|brew|bundle|gem|git|node|rails|rak
 module RailsGuides
   class Markdown
     class Renderer < Redcarpet::Render::HTML  # :nodoc:
+      APPLICATION_FILEPATH_REGEXP = /(app|config|db|lib|test)\//
+      ERB_FILEPATH_REGEXP = /^<%# #{APPLICATION_FILEPATH_REGEXP}.* %>/o
+      RUBY_FILEPATH_REGEXP = /^# #{APPLICATION_FILEPATH_REGEXP}/o
+
       cattr_accessor :edge, :version
 
       def block_code(code, language)
@@ -78,6 +82,7 @@ module RailsGuides
         end
 
         def clipboard_content(code, language)
+          # Remove prompt and results of commands.
           prompt_regexp =
             case language
             when "bash"
@@ -90,6 +95,19 @@ module RailsGuides
             code = code.lines.grep(prompt_regexp).join.gsub(prompt_regexp, "")
           end
 
+          # Remove comments that reference an application file.
+          filepath_regexp =
+            case language
+            when "erb", "html+erb"
+              ERB_FILEPATH_REGEXP
+            when "ruby", "yaml", "yml"
+              RUBY_FILEPATH_REGEXP
+            end
+
+          if filepath_regexp
+            code = code.lines.grep_v(filepath_regexp).join
+          end
+
           ERB::Util.html_escape(code)
         end