Skip required options when using help option

This lets users use `cve list -h` without having to also specify
auth-related options (user, org, api key) that are required for non-help
actions.

cvelib/cli.py

@@ -210,7 +210,25 @@ def init_cve_api(self) -> CveApi:
         )
 
 
-@click.group(context_settings=CONTEXT_SETTINGS)
+class SkipRequiredOnHelp(click.Group):
+    def parse_args(self, ctx: click.Context, args: list) -> list:
+        """If any help options are used, mark global required options as not required.
+
+        That way, we can skip directly to showing the help without requiring users to specify
+        values that don't end up getting used anyway.
+        """
+        if any(arg in ctx.help_option_names for arg in args):
+            # Iterate over all options and flip them to not required and not to prompt for input.
+            for param in self.params:
+                if isinstance(param, click.Option):
+                    param.required = False
+                    # Type ignored due to `"Option" has no attribute "prompt_required"` error:
+                    # https://github.com/pallets/click/blob/d0af32d8/src/click/core.py#L2455
+                    param.prompt_required = False  # type: ignore
+        return super(SkipRequiredOnHelp, self).parse_args(ctx, args)
+
+
+@click.group(context_settings=CONTEXT_SETTINGS, cls=SkipRequiredOnHelp)
 @click.option(
     "-u", "--username", envvar="CVE_USER", required=True, help="Your username (env var: CVE_USER)"
 )

tests/test_cli.py

@@ -559,3 +559,22 @@ def test_show_org():
             "├─ Created:\tWed Apr 21 02:09:07 2021 +0000\n"
             "└─ Modified:\tWed Apr 21 02:09:07 2021 +0000\n"
         )
+
+
+class TestSubcommandHelp:
+    def test_required_opts(self):
+        with mock.patch("cvelib.cli.CveApi.show_org") as show_org:
+            show_org.return_value = {}
+            runner = CliRunner()
+            result = runner.invoke(cli, ["org"])
+            assert result.exit_code == 2, result.output
+            assert "Error: Missing option" in result.output
+
+    def test_exit_on_help(self):
+        with mock.patch("cvelib.cli.CveApi.show_org") as show_org:
+            show_org.return_value = {}
+            runner = CliRunner()
+            result = runner.invoke(cli, ["org", "--help"])
+            assert result.exit_code == 0, result.output
+            # The command is named after the function that is called.
+            assert result.output.startswith("Usage: cli org")