Re: [RFC PATCH 2/3] grep: honor sparse checkout patterns

On Tue, Mar 24, 2020 at 12:12 PM Derrick Stolee [off-list ref] wrote:

On 3/24/2020 3:15 AM, Elijah Newren wrote:

quoted

On Mon, Mar 23, 2020 at 11:12 PM Matheus Tavares
[off-list ref] wrote:

quoted

Also, if I understand correctly, the index doesn't hold paths to dirs,
right? So even if a complete dir is excluded from sparse checkout, we
still have to check all its subentries, only to discover that they
should all be skipped from the search. However, if we were to check
against the sparsity patterns directly (e.g. with the function above),
we could skip such directories together with all their entries.

When in cone mode, we can check if a directory is one of these three
modes:

1. Completely contained in the cone (recursive match)
2. Completely outside the cone
3. Neither. Keep matching subdirectories. (parent match)

The clear_ce_flags() code in dir.c includes the matching algorithms
for this. Hopefully you can re-use a lot of it. You may need to extract
some methods to use them from the grep code.

Thanks for the pointer! I will take a look at the code in dir.c.

quoted

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diff --git a/t/t7817-grep-sparse-checkout.sh b/t/t7817-grep-sparse-checkout.sh
new file mode 100755
index 0000000000..fccf44e829

...

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+       cat >.git/info/sparse-checkout <<-EOF &&
+       /*
+       !/b
+       !/dir
+       EOF
+       git sparse-checkout init &&

Using `git sparse-checkout init` but then manually writing to
.git/info/sparse-checkout?  Seems like it'd make more sense to use
`git sparse-checkout set` than writing the patterns directly yourself.
Also, would prefer to have the examples use cone mode (even if you
have to add subdirectories), as it makes the testcase a bit easier to
read and more performant, though neither is a big deal.

I agree that we should use the builtin so your test script is less
brittle to potential back-end changes to sparse-checkout (none planned).

Makes sense!

I do recommend having at least one test with non-cone mode patterns,
especially if you are checking the pattern-matching yourself instead of
relying on the index.

OK, I will leave at least one test with non-cone patterns then. Thanks
for the comments!