default-path isn't empty, it is used. Otherwise:
1) If tmux neww is run from the command line, the working directory of the
client is used.
2) Otherwise use some platform specific code to retrieve the current working
directory of the process in the active pane.
3) If that fails, the directory where the session was created is used.
Idea and support code, Linux, Solaris, FreeBSD bits by Romain Francoise,
OpenBSD bits by me.
by reading argv[0] from the process group leader of the group that owns the tty
(tcgetpgrp()). This can't be done portably so some OS-dependent code is
introduced (ugh); OpenBSD, FreeBSD and Linux are supported at the moment.
A new window flag, automatic-rename, is available: if this is set to off, the
window name is not changed. Specifying a name with the new-window, new-session
or rename-window commands will automatically set this flag to off for the
window in question. To disable it entirely set the option to off globally (setw
-g automatic-rename off).
Nicholas Marriott