minimize: warn user if '--target' is omitted

- Added logic to check if TARGET has not been provided by the user and output a
  warning to the user.  This fixes #70.
- Added unit test to confirm that missing '--target' is properly reported.

ksconf/commands/minimize.py

@@ -19,6 +19,7 @@
 from ksconf.commands import KsconfCmd, dedent, ConfFileType
 from ksconf.conf.delta import compare_cfgs, DIFF_OP_DELETE, DIFF_OP_EQUAL, DiffStanza, \
     DIFF_OP_INSERT, DIFF_OP_REPLACE, show_diff
+from ksconf.consts import EXIT_CODE_MISSING_ARG
 from ksconf.conf.merge import merge_conf_dicts
 from ksconf.conf.parser import GLOBAL_STANZA, _drop_stanza_comments
 from ksconf.conf.parser import PARSECONF_STRICT, PARSECONF_LOOSE
@@ -84,6 +85,9 @@ def register_args(self, parser):
             "Specify attributes that should always be kept.")
 
     def run(self, args):
+        if not args.target:
+            self.stderr.write("You must specify the target file with '--target'.\n")
+            return EXIT_CODE_MISSING_ARG
         if args.explode_default:
             # Is this the SAME as exploding the defaults AFTER the merge?;
             # I think NOT.  Needs testing

tests/test_cli_minimize.py

@@ -83,6 +83,17 @@ def test_minimize_explode_defaults(self):
             self.assertTrue(orig_size > final_size)
 
 
+    def test_missing_target(self):
+        twd = TestWorkDir()
+        local = twd.copy_static("inputs-ta-nix-local.conf", "inputs.conf")
+        default = static_data("inputs-ta-nix-default.conf")
+        inputs_min = twd.get_path("inputs-new.conf")
+        rebuilt = twd.get_path("inputs-rebuild.conf")
+        with ksconf_cli:
+            ko = ksconf_cli("minimize", "--output", inputs_min, local, default)
+            self.assertEqual(ko.returncode, EXIT_CODE_MISSING_ARG)
+            self.assertIn("--target", ko.stderr)
+
 
 if __name__ == '__main__':  # pragma: no cover
     unittest.main()