Fix clean not respecting defaults

Previously, clean read the defaults once, and then it updated the
setting for each entry it read. This resulted in the defaults being
clobbered and then not being respected for subsequent entries. This
patch fixes the issue by re-reading the defaults before processing each
item.

The other plugins (link, shell) do not have this problem.

dotbot/plugins/clean.py

@@ -18,9 +18,9 @@ class Clean(dotbot.Plugin):
     def _process_clean(self, targets):
         success = True
         defaults = self._context.defaults().get(self._directive, {})
-        force = defaults.get('force', False)
         for target in targets:
-            if isinstance(targets, dict):
+            force = defaults.get('force', False)
+            if isinstance(targets, dict) and isinstance(targets[target], dict):
                 force = targets[target].get('force', force)
             success &= self._clean(target, force)
         if success:

test/tests/clean-default.bash

@@ -0,0 +1,19 @@
+test_description='clean uses default unless overridden'
+. '../test-lib.bash'
+
+test_expect_success 'setup' '
+ln -s /nowhere ~/.g
+'
+
+test_expect_success 'run' '
+run_dotbot <<EOF
+- clean:
+    ~/nonexistent:
+      force: true
+    ~/:
+EOF
+'
+
+test_expect_success 'test' '
+test -h ~/.g
+'