Avoid copy() calls in adjust()

Replace `.pop()` calls with skipping "control" keys (when,because..)
during the merge.

fmf/base.py

@@ -24,6 +24,7 @@
 SUFFIX = ".fmf"
 MAIN = "main" + SUFFIX
 IGNORED_DIRECTORIES = ['/dev', '/proc', '/sys']
+ADJUST_CONTROL_KEYS = ['because', 'continue', 'when']
 
 
 # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -220,6 +221,9 @@ def _merge_minus(self, data, key, value):
     def _merge_special(self, data, source):
         """ Merge source dict into data, handle special suffixes """
         for key, value in sorted(source.items()):
+            # Merge only attribute keys, not the adjust control keys
+            if key in ADJUST_CONTROL_KEYS:
+                continue
             # Handle special attribute merging
             if key.endswith('+'):
                 self._merge_plus(data, key.rstrip('+'), value)
@@ -372,7 +376,7 @@ class describing the environment context. By default, the key
 
         # Adjust rules should be a dictionary or a list of dictionaries
         try:
-            rules = copy.deepcopy(self.data[key])
+            rules = self.data[key]
             log.debug("Applying adjust rules for '{}'.".format(self))
             log.data(rules)
             if isinstance(rules, dict):
@@ -394,29 +398,24 @@ class describing the environment context. By default, the key
             if not isinstance(rule, dict):
                 raise utils.FormatError("Adjust rule should be a dictionary.")
 
-            original_rule = rule.copy()
-
             # Missing 'when' means always enabled rule
             try:
-                condition = rule.pop('when')
+                condition = rule['when']
             except KeyError:
                 condition = True
 
             # The optional 'continue' key should be a bool
-            continue_ = rule.pop('continue', True)
+            continue_ = rule.get('continue', True)
             if not isinstance(continue_, bool):
                 raise utils.FormatError(
                     "The 'continue' value should be bool, "
                     "got '{}'.".format(continue_))
 
-            # The 'because' key is reserved for optional comments (ignored)
-            rule.pop('because', None)
-
             # Apply remaining rule attributes if context matches
             try:
                 if context.matches(condition):
                     if decision_callback:
-                        decision_callback(self, original_rule, True)
+                        decision_callback(self, rule, True)
 
                     self._merge_special(self.data, rule)
 
@@ -425,11 +424,11 @@ class describing the environment context. By default, the key
                         break
                 else:
                     if decision_callback:
-                        decision_callback(self, original_rule, False)
+                        decision_callback(self, rule, False)
             # Handle undecided rules as requested
             except fmf.context.CannotDecide:
                 if decision_callback:
-                    decision_callback(self, original_rule, None)
+                    decision_callback(self, rule, None)
 
                 if undecided == 'skip':
                     continue