Fixing Encoding::CompatibilityError with Ruby 1.9 + ERB, by copying m…

…agic comment to the first line so that it works.

lib/tilt.rb

@@ -189,9 +189,16 @@ def self.evaluate(scope, locals, &block)
     # easier and more appropriate.
     def precompiled(locals)
       preamble = precompiled_preamble(locals)
+      template = precompiled_template(locals)
+      magic_comment = extract_magic_comment(template)
+      if magic_comment
+        # Magic comment e.g. "# coding: utf-8" has to be in the first line.
+        # So we copy the magic comment to the first line.
+        preamble = magic_comment + "\n" + preamble
+      end
       parts = [
         preamble,
-        precompiled_template(locals),
+        template,
         precompiled_postamble(locals)
       ]
       [parts.join("\n"), preamble.count("\n") + 1]
@@ -282,6 +289,10 @@ def unbind_compiled_method(method_name)
       method
     end
 
+    def extract_magic_comment(script)
+      script.slice(/\A[ \t]*\#.*coding\s*[=:]\s*([[:alnum:]\-_]+).*$/)
+    end
+
     # Special case Ruby 1.9.1's broken yield.
     #
     # http://github.com/rtomayko/tilt/commit/20c01a5