allow prefixed @id attributes to allow internal linking

lib/gollum/sanitization.rb

@@ -47,6 +47,25 @@ class Sanitization
       'img' => {'src'  => ['http', 'https', :relative]}
     }.freeze
 
+    # Default transformers to force @id attributes with 'wiki-' prefix
+
+    TRANSFORMERS = [
+      lambda do |env|
+        node      = env[:node]
+        return if env[:is_whitelisted] || !node.element? || !node['id'] 
+        prefix = env[:config][:id_prefix]
+        node['id'] = node['id'].gsub(/\A(#{prefix})?/, prefix)
+
+        {:node_whitelist => [node]}
+      end,
+      lambda do |env|
+        node = env[:node]
+        return unless node['href']
+        prefix = env[:config][:id_prefix]
+        node['href'] = node['href'].gsub(/\A\#(#{prefix})?/, '#'+prefix)
+      end
+    ].freeze
+
     # Gets an Array of whitelisted HTML elements.  Default: ELEMENTS.
     attr_reader :elements
 
@@ -58,6 +77,13 @@ class Sanitization
     # attributes.  Default: PROTOCOLS
     attr_reader :protocols
 
+    # Gets a Hash describing which URI protocols are allowed in HTML 
+    # attributes.  Default: TRANSFORMERS
+    attr_reader :transformers
+
+    # Gets a String prefix which is added to ID attributes. Default: 'wiki-'
+    attr_reader :id_prefix
+
     # Gets a Hash describing HTML attributes that Sanitize should add.  
     # Default: {}
     attr_reader :add_attributes
@@ -70,8 +96,10 @@ def initialize
       @elements       = ELEMENTS
       @attributes     = ATTRIBUTES
       @protocols      = PROTOCOLS
+      @transformers   = TRANSFORMERS
       @add_attributes = {}
       @allow_comments = false
+      @id_prefix      = 'wiki-'
       yield self if block_given?
     end
 
@@ -100,7 +128,9 @@ def to_hash
         :attributes     => attributes,
         :protocols      => protocols,
         :add_attributes => add_attributes,
-        :allow_comments => allow_comments?
+        :allow_comments => allow_comments?,
+        :transformers   => transformers,
+        :id_prefix      => id_prefix
       }
     end
 

test/test_markup.rb

@@ -467,6 +467,20 @@
     compare(content, output, 'org')
   end
 
+  test "id with prefix ok" do
+    content = "h2(example#wiki-foo). xxxx"
+    output = %(<h2 class="example" id="wiki-foo">xxxx</h2>)
+    compare(content, output, :textile)
+  end
+
+  test "id prefix added" do
+    content = "h2(#foo). xxxx[1]\n\nfn1.footnote"
+    output = "<h2 id=\"wiki-foo\">xxxx" +
+             "<sup class=\"footnote\"><a href=\"#wiki-fn1\">1</a></sup></h2>" +
+             "\n<p class=\"footnote\" id=\"wiki-fn1\"><sup>1</sup> footnote</p>"
+    compare(content, output, :textile)
+  end
+
   #########################################################################
   #
   # TeX