Ultimately, users will probably pick either 'master' or 'next' to submit
changes anyway, so just leave the instructions to refer to 'next' and
note that they could replace 'next' with 'master'.
Most Gitorious users know this procedure, but it seems useful to
document it in great detail here, since copyleft.org seeks contributions
from those who might be knew to Git, and those who are more familiar
with procedures of other collaboration sites.
