doc :anchor option for #match in routes

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -364,6 +364,13 @@ def root(options = {})
         #     match 'path' => 'c#a', :defaults => { :format => 'jpg' }
         #
         #   See <tt>Scoping#defaults</tt> for its scope equivalent.
+        #
+        # [:anchor]
+        #   Boolean to anchor a #match pattern. Default is true. When set to
+        #   false, the pattern matches any request prefixed with the given path.
+        #
+        #     # Matches any request starting with 'path'
+        #     match 'path' => 'c#a', :anchor => false
         def match(path, options=nil)
           mapping = Mapping.new(@set, @scope, path, options || {}).to_route
           @set.add_route(*mapping)