Add depri subcommand to remove priorities.

Also guard the set_priority method in TodoList a bit more, to
prevent the dirty bit to be set when an equal priority is passed
on.

DepriCommand.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from Command import *
+from PrettyPrinter import pretty_print
+from TodoList import InvalidTodoException
+from Utils import *
+
+class DepriCommand(Command):
+    def __init__(self, p_args, p_todolist,
+                 p_out=lambda a: None,
+                 p_err=lambda a: None,
+                 p_prompt=lambda a: None):
+        super(DepriCommand, self).__init__(p_args, p_todolist, p_out, p_err, p_prompt)
+
+    def execute(self):
+        if not super(DepriCommand, self).execute():
+            return False
+
+        number = None
+        todo = None
+        try:
+            number = convert_todo_number(self.argument(0))
+            todo = self.todolist.todo(number)
+
+            if todo.priority() != None:
+                self.todolist.set_priority(todo, None)
+                self.out("Priority removed.")
+                self.out(pretty_print(todo))
+        except InvalidCommandArgument:
+            self.error(self.usage())
+        except (InvalidTodoNumberException, InvalidTodoException):
+            if not todo:
+                self.error( "Invalid todo number given.")
+            else:
+                self.error(self.usage())
+
+    def usage(self):
+        return """Synopsis: depri <NUMBER>"""
+
+    def help(self):
+        return """Removes the priority of the given todo item."""

Main.py

@@ -24,6 +24,7 @@ from AddCommand import AddCommand
 from AppendCommand import AppendCommand
 from ArchiveCommand import ArchiveCommand
 from DepCommand import DepCommand
+from DepriCommand import DepriCommand
 import Config
 from DoCommand import DoCommand
 from ListCommand import ListCommand
@@ -102,6 +103,7 @@ class CLIApplication(object):
           'app': AppendCommand,
           'append': AppendCommand,
           'dep': DepCommand,
+          'depri': DepriCommand,
           'do': DoCommand,
           'ls': ListCommand,
           'lscon': ListContextCommand,

TodoList.py

@@ -299,6 +299,7 @@ class TodoList(object):
         self.dirty = True
 
     def set_priority(self, p_todo, p_priority):
+        if p_todo.priority() != p_priority:
             p_todo.set_priority(p_priority)
             self.dirty = True
 

test/DepriCommandTest.py

+# Topydo - A todo.txt client written in Python.
+# Copyright (C) 2014 Bram Schoenmakers <me@bramschoenmakers.nl>
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import CommandTest
+import DepriCommand
+import TodoList
+
+class DepriCommandTest(CommandTest.CommandTest):
+    def setUp(self):
+        todos = [
+            "(A) Foo",
+            "Bar",
+        ]
+
+        self.todolist = TodoList.TodoList(todos)
+
+    def test_set_prio1(self):
+        command = DepriCommand.DepriCommand(["1"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertTrue(self.todolist.is_dirty())
+        self.assertEquals(self.todolist.todo(1).priority(), None)
+        self.assertEquals(self.output, "Priority removed.\nFoo\n")
+        self.assertEquals(self.errors, "")
+
+    def test_set_prio2(self):
+        command = DepriCommand.DepriCommand(["2"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertFalse(self.todolist.is_dirty())
+        self.assertEquals(self.todolist.todo(2).priority(), None)
+        self.assertEquals(self.output, "")
+        self.assertEquals(self.errors, "")
+
+    def test_invalid1(self):
+        command = DepriCommand.DepriCommand(["99"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertFalse(self.todolist.is_dirty())
+        self.assertFalse(self.output)
+        self.assertEquals(self.errors, "Invalid todo number given.\n")
+
+    def test_empty(self):
+        command = DepriCommand.DepriCommand([], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertFalse(self.todolist.is_dirty())
+        self.assertFalse(self.output)
+        self.assertEquals(self.errors, command.usage() + "\n")
+
+    def test_help(self):
+        command = DepriCommand.DepriCommand(["help"], self.todolist, self.out, self.error)
+        command.execute()
+
+        self.assertEquals(self.output, "")
+        self.assertEquals(self.errors, command.usage() + "\n\n" + command.help() + "\n")