Re: the opposite of .gitignore, whitelist

[Jeff King <peff@peff.net>]

On Thu, Oct 25, 2018 at 10:38:46AM -0400, Jason Cooper wrote:

> On 10/25/18 1:37 AM, Junio C Hamano wrote:
> > "lhf635@163.com" <lhf635@163.com> writes:
> >
> >> I have a good idea, add a file to git that is the opposite of .gitignore...,
> > Do negative patterns in .gitignore file help without inventing
> > anything new?
> I did this several years ago in an attempt to track /etc/ (minus
> ownership, of course) without storing secrets in the git history.  As
> the system grew and was maintained (read: crap added), the negative
> patterns grew untenable.  I quickly realized it wasn't the correct way
> to solve the problem.
> 
> Unfortunately, shortly after realizing this, I left that project.  So I
> never had the chance to develop a proper solution.  However, the concept
> of a '.gitonly' file was exactly was I was seeking.  So, for what it's
> worth, I've definitely had at least one legit usecase for this feature.
> 
> The usecases tend to center around tracking select files within the
> rootfs of a full-blown operating system.  Or a subset thereof.

I think what Junio meant is to ignore everything by default, like:

  echo '*' >.gitignore

and then selectively use negative patterns (and being in .gitignore,
that makes them positive "yes, include this") to add things back:

  echo 'foo' >>.gitignore

which ends up being roughly the same as your .gitonly concept.

I don't offhand remember if you might run into problems where a
subdirectory is ignored by the "*" and we do not even recurse into it. I
think it would work OK as long as you put everything in the top-level
gitignore, like:

  echo 'subdir/file' >>.gitignore

but I didn't test.

-Peff