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Re: How to undo previously set configuration? (again)

On Wed, May 1, 2019 at 7:18 PM Ævar Arnfjörð Bjarmason <avarab@xxxxxxxxx> wrote:
> On Wed, May 01 2019, Duy Nguyen wrote:
> > On Wed, May 1, 2019 at 4:14 AM Jeff King <peff@xxxxxxxx> wrote:
> >> It's definitely not implemented universally; each consumer of the config
> >> option must decide on it (and it will probably always be that way to
> >> some degree, since we don't know the semantics of each options; recall
> >> that we may be holding config keys for other non-core programs, too).
> >> And we just haven't retro-fitted a lot of those older options because
> >> nobody has been bothered by it.
> >>
> >> That said, I am a proponent of having some kind of clearing mechanism
> >> (and I was the one who added credential.helper's mechanism, which has
> >> been mentioned in this thread).  I think it makes things a lot less
> >> difficult if we don't have to change the syntax of the config files to
> >> do it. With that constraint, that pretty much leaves:
> >>
> >>   1. Some sentinel value like the empty string. That one _probably_
> >>      works in most cases, but there may be lists which want to represent
> >>      the empty value. There could be other sentinel values (e.g.,
> >>      "CLEAR") which are simply unlikely to be used as real values.
> >>
> >>   2. The boolean syntax (i.e., "[foo]bar" with no equals) is almost
> >>      always bogus for a list. So that can work as a sentinel that is
> >>      OK syntactically.
> >
> > Another question about the universal clearing mechanism, how does "git
> > config" fit into this? It would be great if the user can actually see
> > the same thing a git command sees to troubleshoot. Option 1 leaves the
> > interpretation/guessing to the user, "git config" simply gives the raw
> > input list before "clear" is processed. Option 2, "git config"
> > probably can be taught to optionally clear when it sees the boolean
> > syntax.
> We can make it fancier, but we already deal with this, e.g. if you do
> "git config -l" we'll show "include{,if}" directives at the same "level"
> as other "normal" keys.
> We also provide no way in "git config" to properly interpret a
> value. E.g. does a "user.email" showing up twice for me mean I have two
> E-Mails at the same time, or does the last one win?

Actually --get knows this. Single-valued options can be handled
correctly quite easily. It's --get-all (or rather, the future
--get-multi because we can't change --get-all's behavior) which can't
interpret values because there's no standardized way of doing it.

> We both know the
> answer, but git-config itself doesn't, and that information lives in
> docs/code outside of it.
> Similarly we'd just print a sequence of:
>     user.name=foo
>     user.email=bar
>     exclude.key=user.*
>     user.name=baz
> And it would be up to some "smarter" reader of the config data to
> realize that the end result is one where we have no "user.email" set,
> and "user.name=baz".
> But yeah, optionally having some new --list-normalized or
> --list-after-excludes or whatever would be great, and presumably not
> hard if we had some central "excludes" mechanism...