t: invert `GIT_TEST_WRITE_REV_INDEX`

Back in e8c58f894b (t: support GIT_TEST_WRITE_REV_INDEX, 2021-01-25), we
added a test knob to conditionally enable writing a ".rev" file when
indexing a pack. At the time, this was used to ensure that the test
suite worked even when ".rev" files were written, which served as a
stress-test for the on-disk reverse index implementation.

Now that reading from on-disk ".rev" files is enabled by default, the
test knob `GIT_TEST_WRITE_REV_INDEX` no longer has any meaning.

We could get rid of the option entirely, but there would be no
convenient way to test Git when ".rev" files *aren't* in place.

Instead of getting rid of the option, invert its meaning to instead
disable writing ".rev" files, thereby running the test suite in a mode
where the reverse index is generated from scratch.

This ensures that, when GIT_TEST_NO_WRITE_REV_INDEX is set to some
spelling of "true", we are still running and exercising Git's behavior
when forced to generate reverse indexes from scratch. Do so by setting
it in the linux-TEST-vars CI run to ensure that we are maintaining good
coverage of this now-legacy code.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/t/README b/t/README
index 29576c3748..bdfac4cceb 100644
--- a/t/README
+++ b/t/README
@@ -475,7 +475,7 @@ GIT_TEST_DEFAULT_HASH=<hash-algo> specifies which hash algorithm to
 use in the test scripts. Recognized values for <hash-algo> are "sha1"
 and "sha256".
 
-GIT_TEST_WRITE_REV_INDEX=<boolean>, when true enables the
+GIT_TEST_NO_WRITE_REV_INDEX=<boolean>, when true disables the
 'pack.writeReverseIndex' setting.
 
 GIT_TEST_SPARSE_INDEX=<boolean>, when true enables index writes to use the