build.cmds: Move build.App.cmd_xxx() here

For every cmd_xxx() method in build.App, create a class that's
instatiated for running the respective command. This has the
advantage of making App.py smaller (and faster), and having smaller,
more maintainable command modules adhering to a common interface.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/build/cmds/CmdCommands.py

@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+
+from argparse import Namespace, ArgumentParser
+
+from ..Cmd import Cmd
+
+class CmdCommands(Cmd): # export
+
+    def __init__(self) -> None:
+        super().__init__('commands', help='List available commands')
+
+    def add_arguments(self, parser: ArgumentParser) -> None:
+        super().add_arguments(parser)
+
+    def _run(self, args: Namespace) -> None:
+        import sys, re, os, glob
+        this_dir = os.path.dirname(sys.modules[__name__].__file__)
+        ret = []
+        for file_name in glob.glob('Cmd*.py', root_dir=this_dir):
+            cc_name = re.sub(r'^Cmd|\.py', '', file_name)
+            name = re.sub(r'(?<!^)(?=[A-Z])', '-', cc_name).lower()
+            ret.append(name)
+        print(' '.join(ret))