Re: [PATCH v4 00/10] Sparse index: delete ignored files outside sparse cone

[Elijah Newren <newren@gmail.com>]

On Mon, Aug 30, 2021 at 6:54 AM Derrick Stolee <stolee@gmail.com> wrote:
>
> On 8/27/2021 5:56 PM, Elijah Newren wrote:
> > On Tue, Aug 24, 2021 at 2:51 PM Derrick Stolee via GitGitGadget
> > <gitgitgadget@gmail.com> wrote:
> >>
...
> >>   8:  febef675f05 !  9:  c19d93ec5d7 sparse-checkout: clear tracked sparse dirs
> >>      @@ Commit message
> >>           the sparse directory. This depends on the indexed version of the file,
> >>           so the sparse directory must be expanded.
> >>
> >>      +    We must take special care to look for untracked, non-ignored files in
> >>      +    these directories before deleting them. We do not want to delete any
> >>      +    meaningful work that the users were doing in those directories and
> >>      +    perhaps forgot to add and commit before switching sparse-checkout
> >>      +    definitions. Since those untracked files might be code files that
> >>      +    generated ignored build output, also do not delete any ignored files
> >>      +    from these directories in that case. The users can recover their state
> >>      +    by resetting their sparse-checkout definition to include that directory
> >>      +    and continue. Alternatively, they can see the warning that is presented
> >>      +    and delete the directory themselves to regain the performance they
> >>      +    expect.
> >>      +
> ...
> >>      ++When changing the sparse-checkout patterns in cone mode, Git will inspect each
> >>      ++tracked directory that is not within the sparse-checkout cone to see if it
> >>      ++contains any untracked files. If all of those files are ignored due to the
> >>      ++`.gitignore` patterns, then the directory will be deleted. If any of the
> >>      ++untracked files within that directory is not ignored, then no deletions will
> >>      ++occur within that directory and a warning message will appear. If these files
> >>      ++are important, then reset your sparse-checkout definition so they are included,
> >>      ++use `git add` and `git commit` to store them, then remove any remaining files
> >>      ++manually to ensure Git can behave optimally.
> ...
> > Thanks for the extra explanations; those help.
> >
> > You haven't yet addressed how this choice will interact with
> > .gitignore files, though (as I commented on v3).
...
> The difference between the .gitattributes and .gitignore files is that
> we don't need to do anything with the .gitignore files to prevent Git
> from accessing them with their contained directories don't exist. The
> .gitattributes change in attr.c is reachable from some code path even
> when the directory doesn't exist, so it needs special logic to avoid
> that expansion.

Ah, this is what I was looking for and couldn't quite work out --
whether .gitignore files might need to be loaded (and whether our
other UI decisions were affecting that).  Sounds like you have it
covered.

Thanks for patiently explaining these various items I was not
understanding or missing.  Sorry I missed a couple key things despite
reading the earlier rounds.  Anyway, looks like we're in pretty good
shape and there's only a few minor things left, mostly stuff you
brought up yourself that you wanted to tweak for v5.