Best way to depend on OpenCV master in a Travis CI build-bot instance

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I'm writing a library which depends on the master branch of itseez/opencv, and I'd like to do continuous integration with Travis CI.

What is the best way to get the current (or something close to it) master on a Travis CI instance? (The simple answer is to just do a git clone and build OpenCV from source on the Travis CI instance. But OpenCV may take longer to build than Travis CI allows.)

For example, OpenCV also does continuous integration; is there some way to download the build artifacts, so I don't need to rebuild everything?

Better yet, is debian package creation part of the continuous integration? If so, is there a PPA I can use to grab them?