Adds a base sigint_handler() method to the CommandSet.

The sigint_handler() in Cmd will now delegate to the CommandSet.

Addresses #1197

cmd2/cmd2.py

@@ -535,6 +535,9 @@ def __init__(
         self.suggest_similar_command = suggest_similar_command
         self.default_suggestion_message = "Did you mean {}?"
 
+        # the current command being executed
+        self.current_command: Optional[Statement] = None
+
     def find_commandsets(self, commandset_type: Type[CommandSet], *, subclass_match: bool = False) -> List[CommandSet]:
         """
         Find all CommandSets that match the provided CommandSet type.
@@ -2363,7 +2366,13 @@ def sigint_handler(self, signum: int, _: FrameType) -> None:
 
         # Check if we are allowed to re-raise the KeyboardInterrupt
         if not self.sigint_protection:
-            self._raise_keyboard_interrupt()
+            raise_interrupt = True
+            if self.current_command is not None:
+                command_set = self.find_commandset_for_command(self.current_command.command)
+                if command_set is not None:
+                    raise_interrupt = not command_set.sigint_handler()
+            if raise_interrupt:
+                self._raise_keyboard_interrupt()
 
     def _raise_keyboard_interrupt(self) -> None:
         """Helper function to raise a KeyboardInterrupt"""
@@ -2953,7 +2962,11 @@ def onecmd(self, statement: Union[Statement, str], *, add_to_history: bool = Tru
             ):
                 self.history.append(statement)
 
-            stop = func(statement)
+            try:
+                self.current_command = statement
+                stop = func(statement)
+            finally:
+                self.current_command = None
 
         else:
             stop = self.default(statement)

cmd2/command_definition.py

@@ -165,3 +165,12 @@ def remove_settable(self, name: str) -> None:
             del self._settables[name]
         except KeyError:
             raise KeyError(name + " is not a settable parameter")
+
+    def sigint_handler(self) -> bool:
+        """
+        Handle a SIGINT that occurred for a command in this CommandSet.
+
+        :return: True if this completes the interrupt handling and no KeyboardInterrupt will be raised.
+                 False to raise a KeyboardInterrupt.
+        """
+        return False