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/CmdProjDir.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+
+from argparse import Namespace, ArgumentParser
+
+from ..Cmd import Cmd
+
+class CmdProjDir(Cmd): # export
+
+    def __init__(self) -> None:
+        super().__init__('proj-dir', help='Print directory of a given package')
+
+    def add_arguments(self, parser: ArgumentParser) -> None:
+        super().add_arguments(parser)
+        parser.add_argument('module', nargs='*', help='Modules')
+
+    def _run(self, args: Namespace) -> None:
+        r = []
+        for m in args.module:
+            try:
+                pd = self.app.proj_dir(m)
+                if pd is None:
+                    continue
+                r.append(pd)
+            except Exception as e:
+                self.app.warn(f'No project directory for module "{m}: {e}')
+                continue
+        print(' '.join(r))