Add no_op command (#743)

* Add `no_op` command

* Document `no_op` in `remapping.md`

book/src/remapping.md

@@ -49,4 +49,6 @@ Control, Shift and Alt modifiers are encoded respectively with the prefixes
 | Null         | `"null"`       |
 | Escape       | `"esc"`        |
 
+Keys can be disabled by binding them to the `no_op` command.
+
 Commands can be found in the source code at [`helix-term/src/commands.rs`](https://github.com/helix-editor/helix/blob/master/helix-term/src/commands.rs)

helix-term/src/commands.rs

@@ -162,6 +162,7 @@ impl Command {
 
     #[rustfmt::skip]
     commands!(
+        no_op, "Do nothing",
         move_char_left, "Move left",
         move_char_right, "Move right",
         move_line_up, "Move up",
@@ -361,6 +362,8 @@ impl PartialEq for Command {
     }
 }
 
+fn no_op(_cx: &mut Context) {}
+
 fn move_impl<F>(cx: &mut Context, move_fn: F, dir: Direction, behaviour: Movement)
 where
     F: Fn(RopeSlice, Range, Direction, usize, Movement) -> Range,