General information about contributing to the Android Open Source Project is available at http://source.android.com/ :
The branch strategy for the Developer Tools projects is different from the platform one (described here). Our projects do not have the typical platform release branches (cupcake, donut, eclair, froyo, ...), but instead use branches matching our release cycles.
Our current branches are explained here. External contributions should currently go to studio-1.4-dev.
Before contributing more than a simple bug fix, it is recommended to email the adt-dev mailing list or Google group to make sure that:
If you are looking for ideas on what to contribute, please look at our official bug tracker.