"command_line_encoding=utf8" in texmf.cnf on windows?

[Akira Kakuto]

> For me on windows 10 it only works if I add 
>  command_line_encoding=utf8 
> to my texmf.cnf.
>
> Would it make sense to add this as default to the cnf?
> Or to have an option somewhere to enable it?

The variable affects 4 engines:
pdftex, xetex, uptex, euptex,
and 2 drivers:
dvips, [x]dvipdfmx.

It is known that the setting gives undesirable side effects in a few cases.

I think it is OK to write
command_line_encoding = utf8
in the main texmf-dist/web2c/texmf.cnf,
with documents to kill the effects when bad effects are found:
write a line
command_line_encoding = none
in a texmf.cnf prefered, for example,
texmf-local/web2c/texmf.cnf

If a user does not use non-ascii names, it is best to write
command_line_encoding = none
in a texmf.cnf prefered, for example,
texmf-local/web2c/texmf.cnf

luatex ignores the variable, because context does not run.
To use non-ascii names in luatex, set an option -cmdx
as the "first" option:
luatex -cmdx ...
lualatex -cmdx ...

All the above are for Windows only.

Thanks,
Akira