Pip-tools: add --no-cache option to pip-compile

[mlfz]

A rehash of closed issue #17.

In our CI build script, we use pip-compile to ensure python requirements consistency. Our requirements.in has -e git+ssh://github/... dependencies. As a result, pip-compile checks out the repositories and building up .cache/pip-tools:

build-xenial-01:/home/jenkins$ sudo du -h .cache/pip-tools
120M    .cache/pip-tools/wheels
75G .cache/pip-tools/pkgs
75G .cache/pip-tools

which eventually fills up /home/. Please implement an option for not using cache or clearing cache.

[davidovich]

@mlfz Clearing the cache is already possible:

pip-compile --rebuild

or

pip-compile -r

[mlfz]

Thanks! My apology.