Add an option to lock -r only production dependencies

[notpushkin]

For example, to generate requirements.txt for legacy deployments. Of course, installing all the development dependencies is an option, but it can be hard (i. e. Fabric depends on cryptography which needs some C headers installed, but we don't need Fabric on the server in first place).

This can be tricky, though, depending on how we generate the current pipenv lock -r output.

[notpushkin]

I'm currently using this, but it seems like a bit of a hack:

with open("requirements.txt", "w") as req:
    req.write("# This file is generaged on deploy - do not modify\n\n")
    operations.local("pipenv lock")
    lock = json.load(open("Pipfile.lock"))
    for name, dep in lock["default"].items():
        req.write("{name}{version} --hash={hash}\n".format(
            name=name,
            version=dep["version"],
            hash=dep["hash"]))

[nateprewitt]

Hey @iamale, thanks for taking the time to open this issue. It happens to be a duplicate of #245 where Kenneth decided we won't currently be supporting requirements.txt with a differentiation between dev dependencies.

You'll find a comment here in that issue which notes a slightly simpler script using Pipenv to create a simplified requirements.txt. This will accomplish what you're currently trying to do.