bug#37189: 25.4.1: vc-hg-ignore implementation is missing

[Dmitry Gutov <dgutov@yandex.ru>]

Hi Eli,

On 13.02.2020 17:21, Eli Zaretskii wrote:
> Dmitry, what happens from here is up to you.  You can decide to accept
> Wolfgang's changes as-is, or you can decide you want to continue
> discussing this with him (in which case I will stay away of the
> discussions) and eventually arrive at some alternative changeset.  Or
> you can make any other decision about this.

I think the first thing I'll have to do is revert a part of an earlier 
patch to vc-default-ignore which changed its semantics a little, because 
it doesn't look like this discussion is going to culminate in a patch 
small enough for emacs-27 anyway.

Then, naturally, we'll have to look for small changes that improve the 
situation but provide as little breakage as possible. I pretty much 
agree that vc-ignore's semantics are not well thought through (or 
documented), and there is space for improvement. But the devil is in the 
details. I do have a few of my own questions/ideas, but I'll leave those 
until later.

> I did arrive at a few conclusions after studying the issues raised in
> the discussions, so if you want, I can post those conclusions FTR, if
> for nothing else.

Yes, of course, please go ahead.