Since "builtin" terminfo definitions were implemented (7cbf52db1b),
the decisions made by tui.c and terminfo.c are more relevant. Exposing
that decision in the 'term' option helps with troubleshooting.
Also: remove code that allowed setting t_Co. `:set t_Co=…` has never
worked; the highlight_spec test asserting that nvim_set_option('t_Co')
_does_ work makes no sense, and should not have worked.
This fixes an apparent difference in behavior between Lua and LuaJIT.
Lua fails to format nil:
test/functional/terminal/tui_spec.lua:381: bad argument #2 to 'format' (string expected, got nil)
To deal with SIGWINCH limitations on Windows, change some resize tests
to _shrink_ the screen width. ... But this didn't work, so still
ignoring those tests on Windows.
The terminfo entry for linux only advertises 8 colours, but nvim tries
to make it display 16 colours anyway, resulting in erroneous SGR control
sequences for colours 8 and above. The Linux kernel terminal emulator
itself has actually understood the 256-colour control sequences since
version 4.8 and the 16-colour control sequences since version 4.9. Thus
we apply the same terminfo fixup as we apply for *xterm* and *256*, to
emit the 16-colour and 256-colour control sequences even if terminfo's
setaf and setab do not advertise them.
Calling cmd.exe in Windows follows a very different pattern from Vim.
The primary difference is that Vim does a nested call to cmd.exe, e.g.
the following call in Vim
system('echo a 2>&1')
spawns the following processes
"C:\Program Files (x86)\Vim\vim80\vimrun" -s C:\Windows\system32\cmd.exe /c (echo a 2^>^&1
^>C:\Users\dummy\AppData\Local\Temp\VIoC169.tmp 2^>^&1)
C:\Windows\system32\cmd.exe /c C:\Windows\system32\cmd.exe /c (echo a 2^>^&1
^>C:\Users\dummy\AppData\Local\Temp\VIo3C6C.tmp 2^>^&1)
C:\Windows\system32\cmd.exe /c (echo a 2>&1
>C:\Users\dummy\AppData\Local\Temp\VIo3C6C.tmp 2>&1)
The escaping with ^ is needed because cmd.exe calls itself and needs to
preserve the special metacharacters for the last call. However in nvim
no nested call is made, system('') spawns a single cmd.exe process.
Setting shellxescape to "" disables escaping with ^.
The previous default for shellxquote=( wrapped any command in
parenthesis, in Vim this is more meaningful due to the use of tempfiles
to store the output and redirection (also see &shellquote). There is
a slight benefit in having the default be empty because some expressions
that run in console will not run within parens e.g. due to unbalanced
double quotes
system('echo "a b')
It looks like Neovim has a bug: if `startinsert` is called using `command()`
then `-- TERMINAL --` gets replaced with `-- --` (and also a cursor appears).
