Update documentation for erb trim syntax. Closes #5651.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4598 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/CHANGELOG

 *SVN*
 
+* Update documentation for erb trim syntax. #5651 [matt@mattmargolis.net]
+
 * Pass :id => nil or :class => nil to error_messages_for to supress that html attribute. #3586 [olivier_ansaldi@yahoo.com, sebastien@goetzilla.info]
 
 * Reset @html_document between requests so assert_tag works. #4810 [jarkko@jlaine.net, easleydp@gmail.com]

actionpack/lib/action_view/base.rb

@@ -11,7 +11,7 @@ class ActionViewError < StandardError #:nodoc:
   # 
   # = ERb
   # 
-  # You trigger ERb by using embeddings such as <% %> and <%= %>. The difference is whether you want output or not. Consider the 
+  # You trigger ERb by using embeddings such as <% %>, <% -%>, and <%= %>. The <%= %> tag set is used when you want output. Consider the 
   # following loop for names:
   #
   #   <b>Names of all the people</b>
@@ -19,12 +19,14 @@ class ActionViewError < StandardError #:nodoc:
   #     Name: <%= person.name %><br/>
   #   <% end %>
   #
-  # The loop is setup in regular embedding tags (<% %>) and the name is written using the output embedding tag (<%= %>). Note that this
+  # The loop is setup in regular embedding tags <% %> and the name is written using the output embedding tag <%= %>. Note that this
   # is not just a usage suggestion. Regular output functions like print or puts won't work with ERb templates. So this would be wrong:
   #
   #   Hi, Mr. <% puts "Frodo" %>
   #
-  # (If you absolutely must write from within a function, you can use the TextHelper#concat)
+  # If you absolutely must write from within a function, you can use the TextHelper#concat
+  #
+  # <%- and -%> suppress leading and trailing whitespace, including the trailing newline, and can be used interchangeably with <% and %>.
   #
   # == Using sub templates
   #