Change ^C to just abort current input

Don't exit the program any more. This mirrors what shells do, and is
useful for aborting a reverse search or a too broken input.

src/main.rs

@@ -27,7 +27,9 @@ fn get_input(rl: &mut Editor<()>) -> Result<String, ReadlineError> {
             line.truncate(line.trim_end().len());
             Ok(line)
         }
-        Err(ReadlineError::Interrupted) | Err(ReadlineError::Eof) => Ok(":q".to_string()),
+        // ^C: like in a shell, abort the current input
+        Err(ReadlineError::Interrupted) => Ok("".to_string()),
+        Err(ReadlineError::Eof) => Ok(":q".to_string()),
         Err(e) => Err(e),
     }
 }