Re: [PATCH 7/7] t7814: show lack of alternate ODB-adding

On Wed, Aug 11, 2021 at 6:55 PM Emily Shaffer [off-list ref] wrote:

On Tue, Aug 10, 2021 at 11:28:45AM -0700, Jonathan Tan wrote:

quoted

The previous patches have made "git grep" no longer need to add
submodule ODBs as alternates, at least for the code paths tested in
t7814. Demonstrate this by making adding a submodule ODB as an alternate
fatal in this test.

Signed-off-by: Jonathan Tan <redacted>
---
 t/t7814-grep-recurse-submodules.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/t/t7814-grep-recurse-submodules.sh b/t/t7814-grep-recurse-submodules.sh
index 828cb3ba58..3172f5b936 100755
--- a/t/t7814-grep-recurse-submodules.sh
+++ b/t/t7814-grep-recurse-submodules.sh

@@ -8,6 +8,9 @@ submodules.

 . ./test-lib.sh

+GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB=1
+export GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB
+
 test_expect_success 'setup directory structure and submodule' '
      echo "(1|2)d(3|4)" >a &&
      mkdir b &&
--

2.33.0.rc1.237.g0d66db33f3-goog

This proof seems pretty handy, assuming nobody else is directly calling
add_to_alternates_memory() (and therefore skipping the envvar check).

Hmm, there is at least one call chain in grep which might end up
calling add_to_alternates_memory() directly (although it only seems to
happen on a very specific case):

        grep_submodule > repo_read_gitmodules >
        config_from_gitmodules > add_to_alternates_memory

We can check that with the following:

git init A
git init A/B
git init A/B/C

echo f >A/B/C/f
git -C A/B/C add f
git -C A/B/C commit -m f

git -C A/B submodule add ./C
git -C A/B commit -m C

git -C A submodule add ./B
git -C A commit -m B

rm B/.gitmodules

gdb -ex 'break add_to_alternates_memory' -ex 'run' --args \
    git grep --recurse-submodules .