gh-27: Add extra help info to argparser and reserve the init arg

pymhf/__init__.py

@@ -89,7 +89,13 @@ def run():
     command_parser = parser.add_subparsers(dest="_command")
 
     # `run` command parser
-    run_parser = command_parser.add_parser("run")
+    run_parser = command_parser.add_parser(
+        "run",
+        help=(
+            "Run the provided plugin name (if registered), or the provided path to a module or single-file "
+            "mod."
+        ),
+    )
     run_parser.add_argument(
         "plugin_name",
         help=(
@@ -98,7 +104,13 @@ def run():
         ),
     )
 
-    config_parser = command_parser.add_parser("config")
+    config_parser = command_parser.add_parser(
+        "config",
+        help=(
+            "Configure the provided plugin name (if registered), or the provided path to a module or "
+            "single-file mod."
+        ),
+    )
     config_parser.add_argument(
         "-o",
         "--open",
@@ -114,6 +126,17 @@ def run():
         ),
     )
 
+    init_parser = command_parser.add_parser(
+        "init", help="[NOT YET IMPLEMENTED] Initialise a new empty project under the given name."
+    )
+    init_parser.add_argument(
+        "plugin_name",
+        help=(
+            "The name of the installed library to run, or the single-file script to run, or the path to a "
+            "folder which contains a library to run locally."
+        ),
+    )
+
     args, extras = parser.parse_known_args()  # noqa
 
     # TODO: The extras can be passed to the registered library in the future.