On Wed, Apr 21, 2021 at 10:27 AM Derrick Stolee <stolee@xxxxxxxxx> wrote:
>
> On 4/20/2021 7:00 PM, Elijah Newren wrote:
> > On Tue, Apr 13, 2021 at 7:01 AM Derrick Stolee via GitGitGadget
> > <gitgitgadget@xxxxxxxxx> wrote:
>
> >> diff --git a/read-cache.c b/read-cache.c
> >> index 29ffa9ac5db9..6308234b4838 100644
> >> --- a/read-cache.c
> >> +++ b/read-cache.c
> >> @@ -1594,6 +1594,9 @@ int refresh_index(struct index_state *istate, unsigned int flags,
> >> if (ignore_skip_worktree && ce_skip_worktree(ce))
> >> continue;
> >>
> >> + if (istate->sparse_index && S_ISSPARSEDIR(ce->ce_mode))
> >> + continue;
> >> +
> >
> > I'm a bit confused about what could trigger ce_skip_worktree(ce) &&
> > !ignore_skip_worktree and why it'd be desirable to refresh
> > skip-worktree entries. However, this is tangential to your patch and
> > has apparently been around since 2009 (in particular, from 56cac48c35
> > ("ie_match_stat(): do not ignore skip-worktree bit with
> > CE_MATCH_IGNORE_VALID", 2009-12-14)).
>
> I did some more digging on this part here. There has been movement in
> this space!
>
> The thing that triggers this ignore_skip_worktree variable inside
> refresh_index() is now the REFRESH_IGNORE_SKIP_WORKTREE flag which was
> introduced recently and is set only by builtin/add.c:refresh(), by
> Matheus: a20f704 (add: warn when asked to update SKIP_WORKTREE entries,
> 2021-04-08).
>
> This means that we can (for now) keep the behavior the same by adding
>
> if (ignore_skip_worktree)
> ensure_full_index(istate);
>
> before the loop. This prevents the expansion during 'git status', but
> requires modification before we are ready for 'git add' to work
> correctly. Specifically, 'git add' currently warns only when adding
> something that exactly matches a tracked file with SKIP_WORKTREE. It
> does _not_ warn when adding something that is untracked but would have
> the SKIP_WORKTREE bit if it was tracked. We will need to add that
> extra warning if we want to avoid expanding during 'git add'.
>
> Alternatively, we can decide to change the behavior here and send an
> error() and return failure if they try to add something that would
> live within a sparse-directory entry. I will think more on this and
> have a good answer before v2 is ready.
See my comments on 01/10; users are already getting surprised by "git
add" today and has been going on for months (though not super
frequently). When they try to "git add" an untracked path that would
not match any path specifications in $GIT_DIR/info/sparse-checkout,
the fact that "git add" doesn't error out (or at the very least give a
warning) causes _subsequent_ commands to surprise the user with their
behavior; the fact that it is some later command that does weird stuff
(removing the file from the working tree) makes it harder for them to
try to understand and make sense of. So, I'd say we do want to change
the behavior here...and not just for sparse-indexes but
sparse-checkouts in general.
As for how this affects the code, I think I'm behind both you and
Matheus on understanding here, but I'm starting to think it was a good
idea for me to spout my offhand comment on what looked like a funny
code smell that I thought was unrelated to your patch. Sounds like it
is causing some good digging...I'll try to read up more on the results
when you send v2. :-)
