split the current pane.
Outputs the pane-id for the newly created pane on success

Usage: wezterm cli split-pane [OPTIONS] [PROG]...

Arguments:
  [PROG]...  Instead of executing your shell, run PROG. For example: `wezterm
             cli split-pane -- bash -l` will spawn bash as if it were a login
             shell

Options:
      --pane-id <PANE_ID>
          Specify the pane that should be split. The default is to use the
          current pane based on the environment variable WEZTERM_PANE
      --horizontal
          Equivalent to `--right`. If neither this nor any other direction is
          specified, the default is equivalent to `--bottom`
      --left
          Split horizontally, with the new pane on the left
      --right
          Split horizontally, with the new pane on the right
      --top
          Split vertically, with the new pane on the top
      --bottom
          Split vertically, with the new pane on the bottom
      --top-level
          Rather than splitting the active pane, split the entire window
      --cells <CELLS>
          The number of cells that the new split should have. If omitted, 50% of
          the available space is used
      --percent <PERCENT>
          Specify the number of cells that the new split should have, expressed
          as a percentage of the available space
      --cwd <CWD>
          Specify the current working directory for the initially spawned
          program
      --move-pane-id <MOVE_PANE_ID>
          Instead of spawning a new command, move the specified pane into the
          newly created split
  -h, --help
          Print help