One solution is to add version to url. Some examples from Google API for Golang (http://code.google.com/p/google-api-go-client/):
code.google.com/p/google-api-go-client/tasks/v1
code.google.com/p/google-api-go-client/books/v1
Depending on git master is cowboy coding at its most cavalier; build systems should prize repeatability above all else.