[PATCH v2 7/8] t: support GIT_TEST_WRITE_REV_INDEX

[Taylor Blau <me@ttaylorr.com>]

Add a new option that unconditionally enables the pack.writeReverseIndex
setting in order to run the whole test suite in a mode that generates
on-disk reverse indexes. Additionally, enable this mode in the second
run of tests under linux-gcc in 'ci/run-build-and-tests.sh'.

Once on-disk reverse indexes are proven out over several releases, we
can change the default value of that configuration to 'true', and drop
this patch.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 builtin/index-pack.c      | 5 ++++-
 builtin/pack-objects.c    | 2 ++
 ci/run-build-and-tests.sh | 1 +
 pack-revindex.h           | 2 ++
 t/README                  | 3 +++
 5 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 03408250b1..0bde325a8b 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -1748,7 +1748,10 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	if (prefix && chdir(prefix))
 		die(_("Cannot come back to cwd"));
 
-	rev_index = !!(opts.flags & (WRITE_REV_VERIFY | WRITE_REV));
+	if (git_env_bool(GIT_TEST_WRITE_REV_INDEX, 0))
+		rev_index = 1;
+	else
+		rev_index = !!(opts.flags & (WRITE_REV_VERIFY | WRITE_REV));
 
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index d784569200..24df0c98f7 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -3601,6 +3601,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 
 	reset_pack_idx_option(&pack_idx_opts);
 	git_config(git_pack_config, NULL);
+	if (git_env_bool(GIT_TEST_WRITE_REV_INDEX, 0))
+		pack_idx_opts.flags |= WRITE_REV;
 
 	progress = isatty(2);
 	argc = parse_options(argc, argv, prefix, pack_objects_options,
diff --git a/ci/run-build-and-tests.sh b/ci/run-build-and-tests.sh
index 6c27b886b8..d1cbf330a1 100755
--- a/ci/run-build-and-tests.sh
+++ b/ci/run-build-and-tests.sh
@@ -22,6 +22,7 @@ linux-gcc)
 	export GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=1
 	export GIT_TEST_MULTI_PACK_INDEX=1
 	export GIT_TEST_ADD_I_USE_BUILTIN=1
+	export GIT_TEST_WRITE_REV_INDEX=1
 	make test
 	;;
 linux-clang)
diff --git a/pack-revindex.h b/pack-revindex.h
index 01622cf21a..7237b2b6f8 100644
--- a/pack-revindex.h
+++ b/pack-revindex.h
@@ -16,6 +16,8 @@
  *   can be found
  */
 
+#define GIT_TEST_WRITE_REV_INDEX "GIT_TEST_WRITE_REV_INDEX"
+
 struct packed_git;
 
 /*
diff --git a/t/README b/t/README
index c730a70770..0f97a51640 100644
--- a/t/README
+++ b/t/README
@@ -439,6 +439,9 @@ 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
+'pack.writeReverseIndex' setting.
+
 Naming Tests
 ------------
 
-- 
2.30.0.138.g6d7191ea01