D_CODER

Below are a few interesting post about preparing package.xml automatically. https://github.com/JitendraZaa/AutoGenerate_Package.xml_Ant http://www.tquila.com/blog/2014/02/11/salesforce-packagexml-builder https://packagebuilder.herokuapp.com/ There is no way to figure out wild card metadata components (*) using API. Also, there is no way to figure out what components are not supported as part of force.com migration tool.  Out of above posts, I found Jitendra's post very interesting and useful. Whereas packagebuilder by Tquila guys, generates an exhaustive list of package.xml file for your organization.  On a side note Tquila guys have build a few interesting heroku apps.  https://sfswitch.herokuapp.com/  - To switch components between orgs.  sforgcompare.herokuapp.com    - To compare metadata between orgs. Watch this space for more info!