Restore the --watcher command line option for backwards compat

It is now deprecated but not removed. And it now applies to all windows
not just initially created ones.

docs/changelog.rst

@@ -18,11 +18,6 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Allow the user to supply a custom Python function to draw tab bar. See
   :opt:`tab_bar_style`
 
-- **Backward incompatibility**: The command line option ``--watcher`` has been
-  removed in favor of the :opt:`watcher` option in :file:`kitty.conf`. It can be set
-  from the command line as: ``kitty -o watcher=/path/to/watcher``. It has the
-  advantage of applying to all windows, not just the initially created ones.
-
 - Add support for reporting mouse events with pixel co-ordinates using the
   ``SGR_PIXEL_PROTOCOL`` introduced in xterm 359
 
@@ -69,6 +64,11 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - Unicode input kitten: Implement scrolling when more results are found than
   the available display space (:pull:`4068`)
 
+- The command line option ``--watcher`` has been deprecated in favor of the
+  :opt:`watcher` option in :file:`kitty.conf`. It has the advantage of
+  applying to all windows, not just the initially created ones. Note that
+  ``--watcher`` now also applies to all windows, not just initially created ones.
+
 
 0.23.1 [2021-08-17]
 ----------------------

kitty/cli.py

@@ -711,6 +711,10 @@ type=bool-set
 Print out information about the selection of fallback fonts for characters not present in the main font.
 
 
+--watcher
+This option is deprecated in favor of the :opt:`watcher` option in kitty.conf and should not be used.
+
+
 --execute -e
 type=bool-set
 !

kitty/main.py

@@ -339,6 +339,10 @@ def _main() -> None:
     opts = create_opts(cli_opts, accumulate_bad_lines=bad_lines)
     init_glfw(opts, cli_opts.debug_keyboard, cli_opts.debug_rendering)
     setup_environment(opts, cli_opts)
+    if cli_opts.watcher:
+        from .window import global_watchers
+        global_watchers.set_extra(cli_opts.watcher)
+        log_error('The --watcher command line option has beed deprecated infavor of using the watcher option in kitty.conf')
     try:
         with setup_profiling(cli_opts):
             # Avoid needing to launch threads to reap zombies

kitty/window.py

@@ -13,7 +13,7 @@ from gettext import gettext as _
 from itertools import chain
 from typing import (
     TYPE_CHECKING, Any, Callable, Deque, Dict, Iterable, List, NamedTuple,
-    Optional, Pattern, Sequence, Tuple, Union, cast
+    Optional, Pattern, Sequence, Tuple, Union
 )
 
 from .child import ProcessDesc
@@ -315,15 +315,30 @@ class EdgeWidths:
         return {'left': self.left, 'right': self.right, 'top': self.top, 'bottom': self.bottom}
 
 
-def global_watchers() -> Watchers:
-    spec = get_options().watcher
-    if getattr(global_watchers, 'options_spec', None) == spec:
-        return cast(Watchers, getattr(global_watchers, 'ans'))
-    from .launch import load_watch_modules
-    ans = load_watch_modules(spec) or Watchers()
-    setattr(global_watchers, 'ans', ans)
-    setattr(global_watchers, 'options_spec', spec)
-    return ans
+class GlobalWatchers:
+
+    def __init__(self) -> None:
+        self.options_spec: Optional[Dict[str, str]] = None
+        self.ans = Watchers()
+        self.extra = ''
+
+    def __call__(self) -> Watchers:
+        spec = get_options().watcher
+        if spec == self.options_spec:
+            return self.ans
+        from .launch import load_watch_modules
+        if self.extra:
+            spec = spec.copy()
+            spec[self.extra] = self.extra
+        self.ans = load_watch_modules(spec.keys()) or self.ans
+        self.options_spec = spec.copy()
+        return self.ans
+
+    def set_extra(self, extra: str) -> None:
+        self.extra = extra
+
+
+global_watchers = GlobalWatchers()
 
 
 class Window: