bpo-36390: Gather IDLE Format menu functions into format.py (GH-14827) (GH-14829)

Add two indent spec methods from editor and Rstrip to existing file.
Tests are not added for indent methods because they need change
in lights of 3.x's prohibition on mixing tabs and spaces.
(cherry picked from commit 1b38922434)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/idlelib/idle_test/test_format.py

@@ -6,6 +6,7 @@ from unittest import mock
 from test.support import requires
 from tkinter import Tk, Text
 from idlelib.editor import EditorWindow
+from idlelib.idle_test.mock_idle import Editor as MockEditor
 
 
 class Is_Get_Test(unittest.TestCase):
@@ -573,5 +574,50 @@ class C1():
         self.assertEqual(ask(), 10)
 
 
+class rstripTest(unittest.TestCase):
+
+    def test_rstrip_line(self):
+        editor = MockEditor()
+        text = editor.text
+        do_rstrip = ft.Rstrip(editor).do_rstrip
+        eq = self.assertEqual
+
+        do_rstrip()
+        eq(text.get('1.0', 'insert'), '')
+        text.insert('1.0', '     ')
+        do_rstrip()
+        eq(text.get('1.0', 'insert'), '')
+        text.insert('1.0', '     \n')
+        do_rstrip()
+        eq(text.get('1.0', 'insert'), '\n')
+
+    def test_rstrip_multiple(self):
+        editor = MockEditor()
+        #  Comment above, uncomment 3 below to test with real Editor & Text.
+        #from idlelib.editor import EditorWindow as Editor
+        #from tkinter import Tk
+        #editor = Editor(root=Tk())
+        text = editor.text
+        do_rstrip = ft.Rstrip(editor).do_rstrip
+
+        original = (
+            "Line with an ending tab    \n"
+            "Line ending in 5 spaces     \n"
+            "Linewithnospaces\n"
+            "    indented line\n"
+            "    indented line with trailing space \n"
+            "    ")
+        stripped = (
+            "Line with an ending tab\n"
+            "Line ending in 5 spaces\n"
+            "Linewithnospaces\n"
+            "    indented line\n"
+            "    indented line with trailing space\n")
+
+        text.insert('1.0', original)
+        do_rstrip()
+        self.assertEqual(text.get('1.0', 'insert'), stripped)
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2, exit=2)