Re: [PATCH 5/6] tests: disable GIT_TEST_SPLIT_INDEX for sparse index tests

On 8/17/2021 1:49 PM, SZEDER Gábor wrote:

The sparse index and split index features are said to be currently
incompatible [1], and consequently GIT_TEST_SPLIT_INDEX=1 might
interfere with the test cases exercising the sparse index feature.
Therefore GIT_TEST_SPLIT_INDEX is already explicitly disabled for the
whole of 't1092-sparse-checkout-compatibility.sh'.  There are,
however, two other test cases exercising sparse index, namely
'sparse-index enabled and disabled' in
't1091-sparse-checkout-builtin.sh' and 'status succeeds with sparse
index' in 't7519-status-fsmonitor.sh', and these two could fail with
GIT_TEST_SPLIT_INDEX=1 as well [2].

Unset GIT_TEST_SPLIT_INDEX and disable the split index in these two
test cases to avoid such interference.

Note that this is the minimal change to merely avoid failures when
these test cases are run with GIT_TEST_SPLIT_INDEX=1.  Interestingly,
though, without these changes the 'git sparse-checkout init --cone
--sparse-index' commands still succeed even with split index, and set
all the necessary configuration variables and create the initial
'$GIT_DIR/info/sparse-checkout' file, but the test failures are caused
by later sanity checks finding that the index is not in fact a sparse
index.  This indicates that 'git sparse-checkout init --sparse-index'
lacks some error checking and its tests lack coverage related to split
index, but fixing those issues (let alone making sparse index
comparible with split index) is beyond the scope of this patch series.

s/comparible/compatible.

I agree that making these two things compatible is not something to
solve today. I'm not sure they should _ever_ be solved because of
the complexity involved (what if the base index is not sparse but
the tip wants to be, or vice-versa?, or if a directory must be
expanded because of a conflict?). They use very different approaches
to solve a similar problem: how to deal with large index files.

* The split index reduces index _write_ time by only editing a diff
  of the base index.

* The sparse index reduces index _read and write_ time by writing a
  smaller index, but only if the user is using cone mode sparse-
  checkout.

 test_expect_success 'sparse-index enabled and disabled' '
-	git -C repo sparse-checkout init --cone --sparse-index &&
-	test_cmp_config -C repo true index.sparse &&
-	test-tool -C repo read-cache --table >cache &&
-	grep " tree " cache &&
-
-	git -C repo sparse-checkout disable &&
-	test-tool -C repo read-cache --table >cache &&
-	! grep " tree " cache &&
-	git -C repo config --list >config &&
-	! grep index.sparse config
+	(
+		sane_unset GIT_TEST_SPLIT_INDEX &&
+		git -C repo update-index --no-split-index &&
+
+		git -C repo sparse-checkout init --cone --sparse-index &&
+		test_cmp_config -C repo true index.sparse &&
+		test-tool -C repo read-cache --table >cache &&
+		grep " tree " cache &&
+
+		git -C repo sparse-checkout disable &&
+		test-tool -C repo read-cache --table >cache &&
+		! grep " tree " cache &&
+		git -C repo config --list >config &&
+		! grep index.sparse config
+	)
 '

This test is safe for now.

 test_expect_success 'status succeeds with sparse index' '

This test is being edited in ds/sparse-index-ignored-files. v3
of the relevant patch was just sent today [1].

[1] https://lore.kernel.org/git/e66106f7a99d94145eec983ea5e72b7cf8a8a479.1629206603.git.gitgitgadget@gmail.com/ (local)

You might want to rebase on top of that topic. The edits to
the test are likely stable now.

Thanks,
-Stolee