Re: Memory leak with sparse-checkout

[Taylor Blau <me@ttaylorr.com>]

On Mon, Sep 20, 2021 at 12:29:36PM -0400, Derrick Stolee wrote:
> > So I think the problem really is that we need to drop existing patterns
> > when re-initializing the sparse-checkout in cone mode. We could try to
> > recognize that existing patterns may already constitute a cone (and/or
> > create a cone that covers the existing patterns).
> >
> > But I think the easiest thing (if a little unfriendly) would be to just
> > drop them and start afresh when re-initializing the sparse-checkout in
> > cone mode.
>
> This isn't sufficient, as a user can modify their .git/info/sparse-checkout
> file whenever they want, so we should fix this bug regardless. We could add
> a "Your existing patterns are not in cone mode" error.
>
> It might still be a good idea to let "git sparse-checkout init --cone"
> overwrite the sparse-checkout file _if the file is not already in cone
> mode_.

I'm not sure how helpful such an error message might be to a user in
this scenario without extra information. After seeing just "this isn't a
cone", it's not clear what they should do other than drop their
sparse-checkout configuration and start over.

It would be nice to have an intermediate step between seeing realizing
that the existing patterns don't form a cone and dropping them.

Perhaps we could include an error message and say something like:

    warning: your sparse-checkout patterns do not from a cone
       hint: to reinitialize your sparse-checkout configuration
       hint: try running:
       hint:
       hint:   git sparse-checkout init --cone --reinitialize

Where `--reinitialize` means to drop existing patterns. I suppose it
could be the default when transitioning from non-cone to cone mode, but
that would defeat the purpose of the warning.

We would probably want to perform this check both during initialization,
and when adding patterns in cone mode. It may also be worthwhile to
check the validity of the cone before running 'list' or 'reapply', too.

Thanks,
Taylor