This was quite famously rather complicated.
We drop a bunch of cases - we can't handle tmux-starting-terminals
100% accurately, so we just don't try. It should be quite rare that
somebody starts a different terminal from tmux.
We drop the `tput` since it is useless (like terminfo in general for
feature-detection, because everyone claims to be xterm).
So we just check if we are in konsole, iTerm, vte or genuine-xterm.
Fixes#3696.
See #3481.
This prints an escape sequence, so it can break scp or similar when
someone has an unqualified
fish_vi_key_bindings
in config.fish and happens to run a terminal that can set the cursor.
I hate doing this but I am tired of touching a fish script as part of
some change and having `make style` radically change it. Which makes
editing fish scripts more painful than it needs to be. It is time to do
a wholesale reformatting of these scripts to conform to the documented
style as implemented by the `fish_indent` program.
We cannot just use TERM = xterm and defined Ss sequence, as some old
vte-based terminals are still in the wild that don't support the
sequence and don't have $VTE_VERSION set.
I have tested this on
- konsole - supported and works ($KONSOLE_PROFILE_NAME)
- new xterm - supported and works ($XTERM_VERSION)
- lxterminal-gtk3 - supported and works ($VTE_VERSION)
- new gnome-terminal - supported and works ($VTE_VERSION)
- lxterminal-gtk2 - not supported and deactivated (no $VTE_VERSION)
- tmux in konsole - works
- tmux in lxterminal-gtk2 - deactivated
and for all supported ones with the respective variable erased, to see
that it is deactivated.
Fixes#3499.
