please change default value of truncate-partial-width-windows to nil

[Drew Adams]

This new variable should not have been given a non-nil default value. Non-nil
overrides the user's preference as expressed via `truncate-lines'.

If a user has nil `truncate-lines' (which is still the _default_ value), then
lines should not be truncated. End of story. That's the meaning of
`truncate-lines' (always has been).

If you want the new variable `truncate-partial-width-windows' to override the
`truncate-lines' behavior, then let it do so for only a *non*-nil value of
`truncate-lines'.

Actually, the most reasonable approach might be to not introduce a new option
(with the confusion of variable interaction and override), but simply to let
`truncate-lines have three possible (buffer-local) values:

nil     - never  truncate lines in the current buffer
t       - always truncate lines in the current buffer
integer - do what integer `truncate-partial-width-windows' does today

(Customize sets the default value, not the buffer-local value, of course.)

Regardless of what you think of that suggestion, the important thing is this: If
`truncate-lines' is nil, then please just do what it says: do not truncate
lines, period.