options: deprecate --input-file

I have no idea why this still exists, since we have --input-ipc-server.
I think there was something about Windows, but the latter option is
implemented even on Windows.

DOCS/interface-changes.rst

@@ -34,6 +34,8 @@ Interface changes
       for software video conversion. These were switched to higher quality since
       mpv 0.30.0 (related to the previous changelog entry). This affects video
       outputs like vo_x11 and vo_drm, and screenshots, but not much else.
+    - deprecate --input-file (there are no plans to remove this short-term,
+      but it will probably eventually go away)
  --- mpv 0.30.0 ---
     - add `--d3d11-output-format` to enable explicit selection of a D3D11
       swap chain format.

DOCS/man/options.rst

@@ -3415,6 +3415,8 @@ Input
     like any other binding). See `INPUT.CONF`_.
 
 ``--input-file=<filename>``
+    Deprecated. Use ``--input-ipc-server``.
+
     Read commands from the given file. Mostly useful with a FIFO. Since
     mpv 0.7.0 also understands JSON commands (see `JSON IPC`_), but you can't
     get replies or events. Use ``--input-ipc-server`` for something

options/options.c

@@ -697,7 +697,8 @@ const m_option_t mp_opts[] = {
 
     OPT_FLAG("input-terminal", consolecontrols, UPDATE_TERM),
 
-    OPT_STRING("input-file", input_file, M_OPT_FILE | UPDATE_INPUT),
+    OPT_STRING("input-file", input_file, M_OPT_FILE | UPDATE_INPUT,
+               .deprecation_message = "use --input-ipc-server"),
     OPT_STRING("input-ipc-server", ipc_path, M_OPT_FILE | UPDATE_INPUT),
 
     OPT_SUBSTRUCT("screenshot", screenshot_image_opts, screenshot_conf, 0),