treewide: always have a valid "index_state.repo" member

When the "repo" member was added to "the_index" in [1] the
repo_read_index() was made to populate it, but the unpopulated
"the_index" variable didn't get the same treatment.

Let's do that in initialize_the_repository() when we set it up, and
likewise for all of the current callers initialized an empty "struct
index_state".

This simplifies code that needs to deal with "the_index" or a custom
"struct index_state", we no longer need to second-guess this part of
the "index_state" deep in the stack. A recent example of such
second-guessing is the "istate->repo ? istate->repo : the_repository"
code in [2]. We can now simply use "istate->repo".

We're doing this by making use of the INDEX_STATE_INIT() macro (and
corresponding function) added in [3], which now have mandatory "repo"
arguments.

Because we now call index_state_init() in repository.c's
initialize_the_repository() we don't need to handle the case where we
have a "repo->index" whose "repo" member doesn't match the "repo"
we're setting up, i.e. the "Complete the double-reference" code in
repo_read_index() being altered here. That logic was originally added
in [1], and was working around the lack of what we now have in
initialize_the_repository().

For "fsmonitor-settings.c" we can remove the initialization of a NULL
"r" argument to "the_repository". This was added back in [4], and was
needed at the time for callers that would pass us the "r" from an
"istate->repo". Before this change such a change to
"fsmonitor-settings.c" would segfault all over the test suite (e.g. in
t0002-gitfile.sh).

This change has wider eventual implications for
"fsmonitor-settings.c". The reason the other lazy loading behavior in
it is required (starting with "if (!r->settings.fsmonitor) ..." is
because of the previously passed "r" being "NULL".

I have other local changes on top of this which move its configuration
reading to "prepare_repo_settings()" in "repo-settings.c", as we could
now start to rely on it being called for our "r". But let's leave all
of that for now, and narrowly remove this particular part of the
lazy-loading.

1. 1fd9ae517c4 (repository: add repo reference to index_state,
   2021-01-23)
2. ee1f0c242ef (read-cache: add index.skipHash config option,
   2023-01-06)
3. 2f6b1eb794e (cache API: add a "INDEX_STATE_INIT" macro/function,
   add release_index(), 2023-01-12)
4. 1e0ea5c4316 (fsmonitor: config settings are repository-specific,
   2022-03-25)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Acked-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 9 deletions

diff --git a/sparse-index.c b/sparse-index.c
index 86e3b99870..147a13386a 100644
--- a/sparse-index.c
+++ b/sparse-index.c
@@ -128,9 +128,6 @@ int is_sparse_index_allowed(struct index_state *istate, int flags)
 	if (!core_apply_sparse_checkout || !core_sparse_checkout_cone)
 		return 0;
 
-	if (!istate->repo)
-		istate->repo = the_repository;
-
 	if (!(flags & SPARSE_INDEX_MEMORY_ONLY)) {
 		int test_env;
 
@@ -327,9 +324,6 @@ void expand_index(struct index_state *istate, struct pattern_list *pl)
 			pl = NULL;
 	}
 
-	if (!istate->repo)
-		istate->repo = the_repository;
-
 	/*
 	 * A NULL pattern set indicates we are expanding a full index, so
 	 * we use a special region name that indicates the full expansion.
@@ -552,9 +546,6 @@ void expand_to_path(struct index_state *istate,
 	if (!istate->sparse_index)
 		return;
 
-	if (!istate->repo)
-		istate->repo = the_repository;
-
 	in_expand_to_path = 1;
 
 	/*