to be used as a login shell inside tmux, so add a default-shell session option.
This sets the shell invoked as a login shell when the default-command option is
empty.
The default option value is whichever of $SHELL, getpwuid(getuid())'s pw_shell
or /bin/sh is valid first.
Based on a diff from martynas@, changed by me to be a session option rather
than a window option.
within tmux.
There is a global environment, copied from the external environment when the
server is started and each sesssion has an (initially empty) session
environment which overrides it.
New commands set-environment and show-environment manipulate or display the
environments.
A new session option, update-environment, is a space-separated list of
variables which are updated from the external environment into the session
environment every time a new session is created - the default is DISPLAY.
terminal to be switched between several different windows and programs
displayed on one terminal be detached from one terminal and moved to another.
ok deraadt pirofti