The idea that the interactive bash prompt isn't set in case of TERM=dumb
is intended to fix problems when other machines log remotely into a
NixOS installation via Tramp. A side-effect that change was, however,
that Emacs' shell-mode no longer had a correct prompt. I suppose the
presence of
INSIDE_EMACS=24.5.2,comint
is a sufficiently unique indication that the current interactive shell
is running inside of an Emacs and that the prompt can thus be configured
safely.
NixOS has a pervasive dependency on bash. For instance, the X11
session script sources /etc/profile to get a reasonable
environment. Thus we should not provide an option to disable bash.
Also, enabling zsh no longer sets ‘users.defaultUserShell’ to zsh, to
prevent a collision with bash's definition of the same
option. (Changing the default shell is also something that should be
left to the user.)
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
