Marshal cmd line args into a requirement set.

def populate_requirement_set(requirement_set,  # type: RequirementSet
                                 args,             # type: List[str]
                                 options,          # type: Values
                                 finder,           # type: PackageFinder
                                 session,          # type: PipSession
                                 name,             # type: str
                                 wheel_cache       # type: Optional[WheelCache]
                                 ):
        # type: (...) -> None
        """
        Marshal cmd line args into a requirement set.
        """
        # NOTE: As a side-effect, options.require_hashes and
        #       requirement_set.require_hashes may be updated

        for filename in options.constraints:
            for req_to_add in parse_requirements(
                    filename,
                    constraint=True, finder=finder, options=options,
                    session=session, wheel_cache=wheel_cache):
                req_to_add.is_direct = True
                requirement_set.add_requirement(req_to_add)

        for req in args:
            req_to_add = install_req_from_line(
                req, None, isolated=options.isolated_mode,
                use_pep517=options.use_pep517,
                wheel_cache=wheel_cache
            )
            req_to_add.is_direct = True
            requirement_set.add_requirement(req_to_add)

        for req in options.editables:
            req_to_add = install_req_from_editable(
                req,
                isolated=options.isolated_mode,
                use_pep517=options.use_pep517,
                wheel_cache=wheel_cache
            )
            req_to_add.is_direct = True
            requirement_set.add_requirement(req_to_add)

        for filename in options.requirements:
            for req_to_add in parse_requirements(
                    filename,
                    finder=finder, options=options, session=session,
                    wheel_cache=wheel_cache,
                    use_pep517=options.use_pep517):
                req_to_add.is_direct = True
                requirement_set.add_requirement(req_to_add)
        # If --require-hashes was a line in a requirements file, tell
        # RequirementSet about it:
        requirement_set.require_hashes = options.require_hashes

        if not (args or options.editables or options.requirements):
            opts = {'name': name}
            if options.find_links:
                raise CommandError(
                    'You must give at least one requirement to %(name)s '
                    '(maybe you meant "pip %(name)s %(links)s"?)' %
                    dict(opts, links=' '.join(options.find_links)))
            else:
                raise CommandError(
                    'You must give at least one requirement to %(name)s '
                    '(see "pip help %(name)s")' % opts)