Tmux: keep same directory in new windows

# open/split windows in the same dir
bind '"' split-window -c "#{pane_current_path}"
bind % split-window -h -c "#{pane_current_path}"
bind c new-window -c "#{pane_current_path}"

In your ~/.tmux.conf.

To source it in your open tmux:
[bash]
:source-file ~/.tmux.conf
[/bash]

Or in any shell:
[bash]
tmux source-file ~/.tmux.conf
[/bash]