Function decide 

pub fn decide(panes: &str, records: &str, save: &str) -> Outcome

Work out what each pane should come back as.

panes is tmux list-panes -a -F '#{pane_id}\t#{session_name}\t#{window_index}\t#{pane_index}' and records is print-cmds. Both are read while the panes are live, which is what makes the join of one moment.