fish-shell/share/functions/fish_title.fish

function fish_title
    # emacs' "term" is basically the only term that can't handle it.
    if not set -q INSIDE_EMACS; or string match -vq '*,term:*' -- $INSIDE_EMACS
        # An override for the current command is passed as the first parameter.
        # This is used by `fg` to show the true process name, among others.
        if set -q argv[1]
            echo -- (string sub -l 20 -- $argv[1]) (prompt_pwd -d 1 -D 0)
        else
            # Don't print "fish" because it's redundant
            set -l command (status current-command)
            if test "$command" = fish
                set command
            end
            echo -- (string sub -l 20 -- $command) (prompt_pwd -d 1 -D 1)
        end
    end
end