Added more rules to work as non core drupal developer

Only track folder: "sites" exluding the rules stated before.
This allow to track only custom modules/themes and/or 3th party
modules/themes.

Drupal.gitignore

@@ -10,6 +10,23 @@ files/
 /LICENSE.txt
 /MAINTAINERS.txt
 /UPGRADE.txt
+robots.txt
 sites/all/README.txt
 sites/all/modules/README.txt
 sites/all/themes/README.txt
+.htaccess
+
+#for non core developer
+#only include "sites" folder without exclusions before
+cron.php
+index.php
+install.php
+update.php
+xmlrpc.php
+/includes
+/misc
+/modules     
+/profiles
+/scripts
+/themes
+