server.settings.Server.environment_all

Costs one tmux command per variable, for the reason given on [Session::environment_all](crate::Session::environment_all): a value containing a newline occupies more than one line of the listing, and a continuation line holding an = cannot be told from the next variable.

Errors

Returns an error when tmux cannot be reached or refuses the listing. An empty map means the server holds nothing, never that the listing failed.