Updated CLI help for 'ansible-galaxy' for 'collection' subcommand (#69458)

* Added YAML header line and link to existing github issue

changelogs/fragments/69458-updated-galaxy-cli-help.yaml

@@ -0,0 +1,3 @@
+---
+bugfixes:
+  - "ansible-galaxy- On giving an invalid subcommand to ansible-galaxy, the help would be shown only for role subcommand (collection subcommand help is not shown). With this change, the entire help for ansible-galaxy (same as ansible-galaxy --help) is displayed along with the help for role subcommand. (https://github.com/ansible/ansible/issues/69009)"

lib/ansible/cli/__init__.py

@@ -372,7 +372,12 @@ class CLI(with_metaclass(ABCMeta, object)):
         if HAS_ARGCOMPLETE:
             argcomplete.autocomplete(self.parser)
 
+        try:
             options = self.parser.parse_args(self.args[1:])
+        except SystemExit as e:
+            if(e.code != 0):
+                self.parser.exit(status=2, message=" \n%s " % self.parser.format_help())
+            raise
         options = self.post_process_args(options)
         context._init_global_context(options)