def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend 

def unpack_url(link, location, download_dir=None,
               only_download=False, session=None, hashes=None):
    """Unpack link.
       If link is a VCS link:
         if only_download, export into download_dir and ignore location
          else unpack into location
       for other types of link:
         - unpack into location
         - if download_dir, copy the file into download_dir
         - if only_download, mark location for deletion

    :param hashes: A Hashes object, one of whose embedded hashes must match,
        or HashMismatch will be raised. If the Hashes is empty, no matches are
        required, and unhashable types of requirements (like VCS ones, which
        would ordinarily raise HashUnsupported) are allowed.
    """
    # non-editable vcs urls
    if is_vcs_url(link):
        unpack_vcs_link(link, location)

    # file urls
    elif is_file_url(link):
        unpack_file_url(link, location, download_dir, hashes=hashes)

    # http urls
    else:
        if session is None:
            session = PipSession()

        unpack_http_url(
            link,
            location,
            download_dir,
            session,
            hashes=hashes
        )
    if only_download:
        write_delete_marker_file(location) 

def is_url(name):
    """Returns true if the name looks like a URL"""
    if ':' not in name:
        return False
    scheme = name.split(':', 1)[0].lower()
    return scheme in ['http', 'https', 'file', 'ftp'] + vcs.all_schemes 

def _get_used_vcs_backend(link):
    for backend in vcs.backends:
        if link.scheme in backend.schemes:
            vcs_backend = backend(link.url)
            return vcs_backend