def main(defs={}):
    """
    The main function.
    :param defs: namespace which may contain additional parameters
    :type defs: dict
    """
    # read additional arguments
    # These arguments will not be defined when StaSh is normally installed,
    # but both selfupdate and tests may specify different values
    # i would like to use argparse here, but this must be compatible with older StaSh versions
    repo = defs.get("_owner", DEFAULT_REPO)                  # owner of repo
    branch = defs.get("_br", DEFAULT_BRANCH)                 # target branch
    is_update = '_IS_UPDATE' in defs                         # True if update
    install_path = defs.get("_target", None)                 # target path
    launcher_path = defs.get("_launcher_path", None)         # target path for launch_stash.py
    force_dist = defs.get("_force_dist", None)               # force install method
    zippath = defs.get("_zippath", None)                     # alternate path of zipfile to use
    dryrun = defs.get("_dryrun", None)                       # do not do anything if True
    asuser = defs.get("_asuser", None)                       # install as user if True
    
    # find out which install to use
    if force_dist is None:
        if IN_PYTHONISTA:
            dist = "pythonista"
        else:
            dist = "setup"
    else:
        dist = force_dist
    
    if dist.lower() == "pythonista":
        if install_path is None:
            install_path = DEFAULT_INSTALL_DIR
        if launcher_path is None:
            launcher_path = os.path.join(BASE_DIR, "Documents", "launch_stash.py")
        pythonista_install(install_path, repo=repo, branch=branch, launcher_path=launcher_path, zippath=zippath, verbose=True)
    elif dist.lower() == "setup":
        setup_install(repo, branch, install_path=install_path, zippath=zippath, dryrun=dryrun, as_user=asuser, verbose=True)
    else:
        raise ValueError("Invalid install type: {}".format(dist))
        
    if not is_update:
        # print additional instructions
        print('Installation completed.')
        print('Please restart Pythonista and run launch_stash.py under the home directory to start StaSh.')

    The main function.
    :param defs: namespace which may contain additional parameters
    :type defs: dict
    
getstash.py