Restore support for highlighting XML-encoded plists

lib/rouge/guessers/disambiguation.rb

@@ -101,6 +101,12 @@ def match?(filename)
 
         Cpp
       end
+
+      disambiguate '*.plist' do
+        next XML if matches?(/\A<\?xml\b/)
+
+        Plist
+      end
     end
   end
 end

lib/rouge/lexers/xml.rb

@@ -7,7 +7,7 @@ class XML < RegexLexer
       title "XML"
       desc %q(<desc for="this-lexer">XML</desc>)
       tag 'xml'
-      filenames *%w(*.xml *.xsl *.rss *.xslt *.xsd *.wsdl *.svg)
+      filenames *%w(*.xml *.xsl *.rss *.xslt *.xsd *.wsdl *.svg *.plist)
       mimetypes *%w(
         text/xml
         application/xml

spec/lexers/plist_spec.rb

@@ -8,11 +8,17 @@
 
     it 'guesses by filename' do
       assert_guess :filename => 'foo.pbxproj'
+      assert_guess :filename => 'foo.plist', :source => 'foo'
     end
 
     it 'guesses by mimetype' do
       assert_guess :mimetype => 'text/x-plist'
       assert_guess :mimetype => 'application/x-plist'
     end
+
+    it 'does not guess XML-encoded plists' do
+      deny_guess :filename => 'foo.plist', :mimetype => 'application/xml'
+      deny_guess :filename => 'foo.plist', :source => '<?xml version="1.0" encoding="UTF-8">'
+    end
   end
 end

spec/lexers/xml_spec.rb

@@ -16,6 +16,8 @@
       assert_guess :filename => 'foo.xsd'
       assert_guess :filename => 'foo.wsdl'
       assert_guess :filename => 'foo.svg'
+      assert_guess :filename => 'foo.plist', :source => '<?xml version="1.0" encoding="utf-8"?>'
+      deny_guess   :filename => 'foo.plist', :source => 'foo'
     end
 
     it 'guesses by mimetype' do