7f104aa6e2
5404595b55eeefae69f2952a34dfc70e32523060 relocated code but kept one backslah too many, leading to $ tmux error creating /run/user/$(id -u)/tmux-1000 (No such file or directory) /run/user/$UID/ is created by pam_systemd(3) which also populates XD_RUNTIME_DIR with that value. Alternatively, TMUX_TMPDIR might simply default to XDG_RUNTIME_DIR without providing the same directory yet again as default string in parameter substitution, however such behaviour change is subject to another patch. In fact, with `security.polkit.enable = false` systemd_logind(8) fails to start and /run/user/$UID/ is never created for unprivileged users in proper login sessions; XDG_RUNTIME_DIR would consequently not be set either. Removing the fallback to /run/user/$UID/ would have caused TMUX_TMPDIR to be empty, which in turn would lead tmux(1) to use /tmp/. This effectively breaks the idea of isolated sockets entirely while hiding errors from the user.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.