Build with the submodule version Sizzle if it exists; otherwise build from the default Sizzle in src/sizzle.js. (We still won't initiate a fetch of the Sizzle submodule, so if the user wants this behavior he/she should grab the submodule manually.) [#1249 state:resolved]

Author: savetheclocktower

Rakefile

@@ -157,10 +157,19 @@ EOF
   end
 
   def self.get_selector_engine(name)
-    return if name == DEFAULT_SELECTOR_ENGINE || !name
+    return if !name
+    # If the submodule exists, we should use it, even if we're using the
+    # default engine; the user might have fetched it manually, and thus would
+    # want to build a distributable with the most recent version of that
+    # engine.
     submodule_path = File.join(ROOT_DIR, "vendor", name)
     return submodule_path if File.exist?(File.join(submodule_path, "repository", ".git"))
     return submodule_path if name === "legacy_selector"
+    
+    # If it doesn't exist, we should fetch it, _unless_ it's the default
+    # engine. We've already got a known version of the default engine in our
+    # load path.
+    return if name == DEFAULT_SELECTOR_ENGINE
     get_submodule('the required selector engine', "#{name}/repository")
     unless File.exist?(submodule_path)
       puts "The selector engine you required isn't available at vendor/#{name}.\n\n"