Requirements files and PEP 508 improvements

[cnpryer]

Summary

PEP 508 details the Dependency specification for Python Software Packages. This would add support for things like initializing a project from requirements files, offer more robustness with less typical specifiers, and more.

Motivation

• Makes onboarding easier
• Can improve on current state of environment reproducibility
• Better integrates with useful standards that make other features less relied on

Requirements

• Allow init-from-requirements
• Allow to-requirements (TODO: Is this worth it?)
• Allow better requirements specification support (cc #833)

Think about SHA-256 digests for transitive deps and more reproducibility work

Details

huak init -r requirements.txt

[cnpryer]

cc #890