Prompt: don't show "todo file modified" warning for readonly commands.

This reuses the logic that the backup functionality uses to determine
whether a command is read-only or not. In that case, prompt mode doesn't
trigger a warning for ls* commands when the backing todo file was
changed.

topydo/cli/CLIApplicationBase.py

@@ -196,13 +196,18 @@ class CLIApplicationBase(object):
         """
         return input
 
+    def is_read_only(self, p_command):
+        """ Returns True when the given command class is read-only. """
+        read_only_commands = tuple(cmd + 'Command' for cmd in ('Revert', ) +
+                READ_ONLY_COMMANDS)
+        return p_command.__module__.endswith(read_only_commands)
+
     def _execute(self, p_command, p_args):
         """
         Execute a subcommand with arguments. p_command is a class (not an
         object).
         """
-        cmds_wo_backup = tuple(cmd + 'Command' for cmd in ('Revert', ) + READ_ONLY_COMMANDS)
-        if config().backup_count() > 0 and p_command and not p_command.__module__.endswith(cmds_wo_backup):
+        if config().backup_count() > 0 and p_command and not self.is_read_only(p_command):
             call = [p_command.__module__.lower()[16:-7]] + p_args # strip "topydo.commands" and "Command"
             self.backup = ChangeSet(self.todolist, p_call=call)
 

topydo/cli/Prompt.py

@@ -99,15 +99,14 @@ class PromptApplication(CLIApplicationBase):
                 sys.exit(0)
 
             mtime_after = _todotxt_mtime()
+            (subcommand, args) = get_subcommand(user_input)
 
-            if self.mtime != mtime_after:
-                # refuse to perform operations such as 'del' and 'do' if the
-                # todo.txt file has been changed in the background.
+            # refuse to perform operations such as 'del' and 'do' if the
+            # todo.txt file has been changed in the background.
+            if not self.is_read_only(subcommand) and self.mtime != mtime_after:
                 error("WARNING: todo.txt file was modified by another application.\nTo prevent unintended changes, this operation was not executed.")
                 continue
 
-            (subcommand, args) = get_subcommand(user_input)
-
             try:
                 if self._execute(subcommand, args) != False:
                     self._post_execute()