Allow to customise shortcuts using a traitlet (#13928) This is a refactor of keybindings code aiming to enable users to modify, disable, and add new shortcuts. Closes #13878, relates to #13879. ## Code changes - The filters are no longer defined as Python condition expression but as strings. This ensures that all shortcuts that we define can be unambiguously overridden by users from JSON config files. - All filters were moved to a new `filters.py` module - All commands previously defined in closure of `create_ipython_shortcuts(shell)` were moved to globals (which ensures nice identifier names and makes unit-testing easier) - All bindings are now collected in `KEY_BINDINGS` global variable; in future one could consider further splitting them up and moving bindings definition to respective modules (e.g. `AUTO_MATCH_BINDINGS` to `auto_match.py`). ## User-facing changes - New configuration traitlet: `c.TerminalInteractiveShell.shortcuts` - Accept single character in autosuggestion shortcut now uses <kbd>alt</kbd> + <kbd>right</kbd> instead of <kbd>right</kbd> (which is accepting the entire suggestion as in versions 8.8 and before). After a few iterations I arrived to a specification that separates the existing key/filter from the new key/filter and has a separate "create" flag used to indicate that a new shortcut should be created (rather than modifying an existing one): > Each entry on the list should be a dictionary with ``command`` key identifying the target function executed by the shortcut and at least one of the following: > - `match_keys`: list of keys used to match an existing shortcut, > - `match_filter`: shortcut filter used to match an existing shortcut, > - `new_keys`: list of keys to set, > - `new_filter`: a new shortcut filter to set > > The filters have to be composed of pre-defined verbs and joined by one of the following conjunctions: `&` (and), `|` (or), `~` (not). The pre-defined verbs are: ..... > > To disable a shortcut set `new_keys` to an empty list. To add a shortcut add key `create` with value `True`. When modifying/disabling shortcuts, `match_keys`/`match_filter` can be omitted if the provided specification uniquely identifies a shortcut to be overridden/disabled. > > When modifying a shortcut `new_filter` or `new_keys` can be omitted which will result in reuse of the existing filter/keys. > > Only shortcuts defined in IPython (and not default prompt toolkit shortcuts) can be modified or disabled.