Converts a Pipfile-formatted dependency to a pip-formatted one.

def convert_deps_to_pip(deps, project=None, r=True, include_index=True):
    """"Converts a Pipfile-formatted dependency to a pip-formatted one."""
    from .vendor.requirementslib.models.requirements import Requirement

    dependencies = []
    for dep_name, dep in deps.items():
        if project:
            project.clear_pipfile_cache()
        indexes = getattr(project, "pipfile_sources", []) if project is not None else []
        new_dep = Requirement.from_pipfile(dep_name, dep)
        if new_dep.index:
            include_index = True
        req = new_dep.as_line(sources=indexes if include_index else None).strip()
        dependencies.append(req)
    if not r:
        return dependencies

    # Write requirements.txt to tmp directory.
    from .vendor.vistir.path import create_tracked_tempfile
    f = create_tracked_tempfile(suffix="-requirements.txt", delete=False)
    f.write("\n".join(dependencies).encode("utf-8"))
    f.close()
    return f.name