[FEATURE] cli-to-sub argument to convert yt-dlp args to ytdl-sub (#1376)

Example usage:
```
$ ytdl-sub cli-to-sub -S vcodec:h264,res:480,acodec:m4a
ytdl_options:
  format_sort:
  - vcodec:h264
  - res:480
  - acodec:m4a
```

docs/source/usage.rst

@@ -105,3 +105,11 @@ Preview the source variables for a given URL. Helpful to create new subscription
 
   -sc, --split-chapters
                         View source variables after splitting by chapters
+
+CLI to SUB Options
+------------------
+Convert yt-dlp cli arguments to ytdl-sub `ytdl_options` arguments.
+
+.. code-block::
+
+   ytdl-sub cli-to-sub [YT-DLP ARGS]

src/ytdl_sub/cli/entrypoint.py

@@ -12,6 +12,7 @@ from yt_dlp.utils import sanitize_filename
 from ytdl_sub.cli.output_summary import output_summary
 from ytdl_sub.cli.output_transaction_log import _maybe_validate_transaction_log_file
 from ytdl_sub.cli.output_transaction_log import output_transaction_log
+from ytdl_sub.cli.parsers.cli_to_sub import print_cli_to_sub
 from ytdl_sub.cli.parsers.dl import DownloadArgsParser
 from ytdl_sub.cli.parsers.main import DEFAULT_CONFIG_FILE_NAME
 from ytdl_sub.cli.parsers.main import parser
@@ -206,6 +207,10 @@ def main() -> List[Subscription]:
 
     args, extra_args = parser.parse_known_args()
 
+    if args.subparser == "cli-to-sub":
+        print_cli_to_sub(args=extra_args)
+        return []
+
     # Load the config
     if args.config:
         config = ConfigFile.from_file_path(args.config)
@@ -263,7 +268,7 @@ def main() -> List[Subscription]:
                 _view_url_from_cli(config=config, url=args.url, split_chapters=args.split_chapters)
             )
         else:
-            raise ValidationException("Must provide one of the commands: sub, dl, view")
+            raise ValidationException("Must provide one of the commands: sub, dl, view, cli-to-sub")
 
     if not args.suppress_transaction_log:
         output_transaction_log(

src/ytdl_sub/cli/parsers/cli_to_sub.py

@@ -0,0 +1,64 @@
+from typing import List
+
+import yt_dlp
+import yt_dlp.options
+
+from ytdl_sub.utils.logger import Logger
+from ytdl_sub.utils.yaml import dump_yaml
+
+logger = Logger.get()
+
+# pylint: disable=missing-function-docstring
+
+##############################################################
+# --- BEGIN ----
+# Copy of https://github.com/yt-dlp/yt-dlp/blob/master/devscripts/cli_to_api.py
+
+create_parser = yt_dlp.options.create_parser
+
+
+def parse_patched_options(opts):
+
+    patched_parser = create_parser()
+    patched_parser.defaults.update(
+        {
+            "ignoreerrors": False,
+            "retries": 0,
+            "fragment_retries": 0,
+            "extract_flat": False,
+            "concat_playlist": "never",
+            "update_self": False,
+        }
+    )
+    yt_dlp.options.create_parser = lambda: patched_parser
+    try:
+        return yt_dlp.parse_options(opts)
+    finally:
+        yt_dlp.options.create_parser = create_parser
+
+
+default_opts = parse_patched_options([]).ydl_opts
+
+
+def cli_to_api(opts, cli_defaults=False):
+    opts = (yt_dlp.parse_options if cli_defaults else parse_patched_options)(opts).ydl_opts
+
+    diff = {k: v for k, v in opts.items() if default_opts[k] != v}
+    if "postprocessors" in diff:
+        diff["postprocessors"] = [
+            pp for pp in diff["postprocessors"] if pp not in default_opts["postprocessors"]
+        ]
+    return diff
+
+
+# --- END ----
+##############################################################
+
+
+def print_cli_to_sub(args: List[str]) -> None:
+    api_args = cli_to_api(args)
+    if not api_args:
+        logger.info("Does not resolve to any yt-dlp args")
+        return
+
+    print(dump_yaml({"ytdl_options": api_args}))

src/ytdl_sub/cli/parsers/main.py

@@ -221,3 +221,7 @@ view_parser.add_argument(
     help="View source variables after splitting by chapters",
 )
 view_parser.add_argument("url", help="URL to view source variables for")
+
+###################################################################################################
+# CLI-TO-SUB PARSER
+cli_to_sub_parser = subparsers.add_parser("cli-to-sub")

tests/unit/main/test_main.py

@@ -244,7 +244,9 @@ def test_no_positional_arg_command(mock_sys_exit, tv_show_config_path):
         main()
 
         assert mock_error.call_count == 1
-        assert mock_error.call_args.args[0] == "Must provide one of the commands: sub, dl, view"
+        assert mock_error.call_args.args[0] == (
+            "Must provide one of the commands: sub, dl, view, cli-to-sub"
+        )
 
 
 def test_bad_config_path(mock_sys_exit):
@@ -264,3 +266,18 @@ def test_bad_config_path(mock_sys_exit):
             "The config file 'does_not_exist.yaml' could not be found. "
             "Did you set --config correctly?"
         )
+
+
+def test_cli_to_sub(mock_sys_exit, capsys):
+    with (
+        mock_sys_exit(expected_exit_code=0),
+        patch.object(
+            sys,
+            "argv",
+            ["ytdl-sub", "cli-to-sub", "--mark-watched", "--mtime"],
+        ),
+    ):
+        main()
+
+    captured = capsys.readouterr()
+    assert captured.out == ("ytdl_options:\n  mark_watched: true\n  updatetime: true\n\n")