def from_line(cls, name, comes_from=None, isolated=False):
        """Creates an InstallRequirement from a name, which might be a
        requirement, directory containing 'setup.py', filename, or URL.
        """
        from pip.index import Link

        url = None
        if is_url(name):
            marker_sep = '; '
        else:
            marker_sep = ';'
        if marker_sep in name:
            name, markers = name.split(marker_sep, 1)
            markers = markers.strip()
            if not markers:
                markers = None
        else:
            markers = None
        name = name.strip()
        req = None
        path = os.path.normpath(os.path.abspath(name))
        link = None

        if is_url(name):
            link = Link(name)
        elif (os.path.isdir(path)
                and (os.path.sep in name or name.startswith('.'))):
            if not is_installable_dir(path):
                raise InstallationError(
                    "Directory %r is not installable. File 'setup.py' not "
                    "found." % name
                )
            link = Link(path_to_url(name))
        elif is_archive_file(path):
            if not os.path.isfile(path):
                logger.warning(
                    'Requirement %r looks like a filename, but the file does '
                    'not exist',
                    name
                )
            link = Link(path_to_url(name))

        # it's a local file, dir, or url
        if link:

            url = link.url
            # Handle relative file URLs
            if link.scheme == 'file' and re.search(r'\.\./', url):
                url = path_to_url(os.path.normpath(os.path.abspath(link.path)))

            # wheel file
            if link.ext == wheel_ext:
                wheel = Wheel(link.filename)  # can raise InvalidWheelFilename
                if not wheel.supported():
                    raise UnsupportedWheel(
                        "%s is not a supported wheel on this platform." %
                        wheel.filename
                    )
                req = "%s==%s" % (wheel.name, wheel.version)
            else:
                # set the req to the egg fragment.  when it's not there, this
                # will become an 'unnamed' requirement
                req = link.egg_fragment

        # a requirement specifier
        else:
            req = name

        return cls(req, comes_from, url=url, markers=markers,
                   isolated=isolated)
Creates an InstallRequirement from a name, which might be a
        requirement, directory containing 'setup.py', filename, or URL.