Bitcoin integration/staging tree
Developers work in their own trees, then submit pull requests when they think their feature or bug fix is ready.
If it is a simple/trivial/non-controversial change, then one of the bitcoin development team members simply pulls it.
If it is a more complicated or potentially controversial change, then the patch submitter will be asked to start a discussion (if they haven't already) on the mailing list: http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-development The patch will be accepted if there is broad consensus that it is a good thing. Developers should expect to rework and resubmit patches if they don't match the project's coding conventions (see coding.txt) or are controversial.
The master branch is regularly built and tested, but is not guaranteed to be completely stable. Tags are regularly created to indicate new official, stable release versions of Bitcoin. If you would like to help test the Bitcoin core, please contact QA@Bitcoin.org.
Feature branches are created when there are major new features being worked on by several people.