Update tmux default directory for new windows

TIL:

• the -c flag to attach-session will update the default current working directory for new windows.
  
• attach-session can be run from the tmux command prompt with an arg of -t . to connect to the current session,
  so we don't need to detach and reattach.
  
• attach also supports -c
  
• tmux makes the current pane's working directory available in the command prompt as '#{pane_current_path}'
  
• new-window also supports the -c option.
  

Set the default CWD for new windows to the current directory:

From the tmux command prompt:

:attach -c '#{pane_current_path}'

# or the more verbose attach-session version,
# listed because I thought of this first :)
:attach-session -t . -c '#{pane_current_path}'

Bound to a char in .tmux.conf:

# update default path for new windows to the current path 
bind-key 'M-/' :attach -c '#{pane_current_path}'

# Open a new window using the current working directory,
bind-key 'C' new-window -c '#{pane_current_path}'

For reference: see this StackOverflow comment and this Unix StackExchange answer.