Initial undo/redo support

Author: lzybkr

PSReadLine/Keys.cs

@@ -107,9 +107,10 @@ public class Keys
         new
         public static ConsoleKeyInfo Equals      = new ConsoleKeyInfo('=', ConsoleKey.OemPlus, false, false, false);
 
-        public static ConsoleKeyInfo CtrlAt    = new ConsoleKeyInfo((char)0, ConsoleKey.D2, true, false, true);
-        public static ConsoleKeyInfo AltEquals = new ConsoleKeyInfo('=', ConsoleKey.OemPlus, false, true, false);
-        public static ConsoleKeyInfo Space     = new ConsoleKeyInfo(' ', ConsoleKey.Spacebar, false, false, false);
+        public static ConsoleKeyInfo CtrlAt       = new ConsoleKeyInfo((char)0, ConsoleKey.D2, true, false, true);
+        public static ConsoleKeyInfo CtrlUnderbar = new ConsoleKeyInfo((char)31, ConsoleKey.OemMinus, true, false, true);
+        public static ConsoleKeyInfo AltEquals    = new ConsoleKeyInfo('=', ConsoleKey.OemPlus, false, true, false);
+        public static ConsoleKeyInfo Space        = new ConsoleKeyInfo(' ', ConsoleKey.Spacebar, false, false, false);
         // Useless because it's caught by the console to bring up the system menu.
         public static ConsoleKeyInfo AltSpace  = new ConsoleKeyInfo(' ', ConsoleKey.Spacebar, false, true, false);
         public static ConsoleKeyInfo CtrlSpace  = new ConsoleKeyInfo(' ', ConsoleKey.Spacebar, false, false, true);

PSReadLine/PSReadLineResources.Designer.cs

@@ -213,8 +213,11 @@
   <data name="PreviousHistoryDescription" xml:space="preserve">
     <value>Replace the input with the previous item in the history</value>
   </data>
+  <data name="RedoDescription" xml:space="preserve">
+    <value>Redo an undo</value>
+  </data>
   <data name="RevertLineDescription" xml:space="preserve">
-    <value>Clear the current input</value>
+    <value>Equivalent to undo all edits (clears the line except lines imported from history)</value>
   </data>
   <data name="SetMarkDescription" xml:space="preserve">
     <value>Mark the location of the cursor</value>
@@ -225,6 +228,9 @@
   <data name="TabCompletePreviousDescription" xml:space="preserve">
     <value>Complete the input using the previous completion</value>
   </data>
+  <data name="UndoDescription" xml:space="preserve">
+    <value>Undo a previous edit</value>
+  </data>
   <data name="YankDescription" xml:space="preserve">
     <value>Copy the text from the current kill ring position to the input</value>
   </data>