bug#34776: 27.0.50; Some questions about choose-completion-string-functions

[Eric Abrahamsen]

I'm trying to use `choose-completion-string-functions' to do some
"stuff" after the user finishes a completion, and have two questions:

1. The docstring of this variable says it is called with three
   arguments, but in fact it's called with four: the fourth is passed as
   nil, and is only there for backward compatibility, apparently. But
   still, you can't use a function that only accepts three args. I can
   provide a patch for the docstring if this is correct.
2. The code in `choose-completion-string' behaves as though the above
   variable is buffer local, but it is never declared to be so. I'm not
   sure if this is a bug (ie, we should be using `defvar-local'), or
   whether I should be adding functions here using the (local 'SYMBOL)
   convention of `add-function'. If that's the case, that's probably
   also a docstring bug, as we should warn users that they'll want to
   specify a local variable.

WDYT?

Eric