[PATCH 5/5] treewide: always have a valid "index_state.repo" member

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

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".

For "fsmonitor-settings.c" we can remove the initialization of a NULL
"r" argument to "the_repository". This was added back in [3], 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. 1e0ea5c4316 (fsmonitor: config settings are repository-specific,
   2022-03-25)

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 apply.c                   |  2 +-
 builtin/difftool.c        |  2 +-
 builtin/sparse-checkout.c |  1 +
 builtin/stash.c           |  8 ++++----
 builtin/worktree.c        |  2 +-
 fsmonitor-settings.c      | 14 --------------
 fsmonitor.c               |  2 +-
 merge-recursive.c         |  2 +-
 read-cache.c              | 10 ++--------
 repository.c              |  2 ++
 revision.c                |  2 +-
 sparse-index.c            |  9 ---------
 split-index.c             |  1 +
 unpack-trees.c            |  1 +
 14 files changed, 17 insertions(+), 41 deletions(-)

diff --git a/apply.c b/apply.c
index 85822280476..47bc6598573 100644
--- a/apply.c
+++ b/apply.c
@@ -4105,7 +4105,7 @@ static int preimage_oid_in_gitlink_patch(struct patch *p, struct object_id *oid)
 static int build_fake_ancestor(struct apply_state *state, struct patch *list)
 {
 	struct patch *patch;
-	struct index_state result = { NULL };
+	struct index_state result = { .repo = state->repo };
 	struct lock_file lock = LOCK_INIT;
 	int res;
 
diff --git a/builtin/difftool.c b/builtin/difftool.c
index 1f9d4324df5..ff29906f64a 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -361,7 +361,7 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	struct hashmap symlinks2 = HASHMAP_INIT(pair_cmp, NULL);
 	struct hashmap_iter iter;
 	struct pair_entry *entry;
-	struct index_state wtindex = { 0 };
+	struct index_state wtindex = { .repo = the_repository };
 	struct checkout lstate, rstate;
 	int err = 0;
 	struct child_process cmd = CHILD_PROCESS_INIT;
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index 58a22503f04..6f0ea71ebb1 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -217,6 +217,7 @@ static int update_working_directory(struct pattern_list *pl)
 	o.head_idx = -1;
 	o.src_index = r->index;
 	o.dst_index = r->index;
+	o.result.repo = r;
 	o.skip_sparse_checkout = 0;
 	o.pl = pl;
 
diff --git a/builtin/stash.c b/builtin/stash.c
index bb0fd861434..a4ff967ea59 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -1137,7 +1137,7 @@ static int save_untracked_files(struct stash_info *info, struct strbuf *msg,
 	int ret = 0;
 	struct strbuf untracked_msg = STRBUF_INIT;
 	struct child_process cp_upd_index = CHILD_PROCESS_INIT;
-	struct index_state istate = { NULL };
+	struct index_state istate = { .repo = the_repository };
 
 	cp_upd_index.git_cmd = 1;
 	strvec_pushl(&cp_upd_index.args, "update-index", "-z", "--add",
@@ -1176,7 +1176,7 @@ static int stash_staged(struct stash_info *info, struct strbuf *out_patch,
 {
 	int ret = 0;
 	struct child_process cp_diff_tree = CHILD_PROCESS_INIT;
-	struct index_state istate = { NULL };
+	struct index_state istate = { .repo = the_repository };
 
 	if (write_index_as_tree(&info->w_tree, &istate, the_repository->index_file,
 				0, NULL)) {
@@ -1209,7 +1209,7 @@ static int stash_patch(struct stash_info *info, const struct pathspec *ps,
 	int ret = 0;
 	struct child_process cp_read_tree = CHILD_PROCESS_INIT;
 	struct child_process cp_diff_tree = CHILD_PROCESS_INIT;
-	struct index_state istate = { NULL };
+	struct index_state istate = { .repo = the_repository };
 	char *old_index_env = NULL, *old_repo_index_file;
 
 	remove_path(stash_index_path.buf);
@@ -1271,7 +1271,7 @@ static int stash_working_tree(struct stash_info *info, const struct pathspec *ps
 	struct rev_info rev;
 	struct child_process cp_upd_index = CHILD_PROCESS_INIT;
 	struct strbuf diff_output = STRBUF_INIT;
-	struct index_state istate = { NULL };
+	struct index_state istate = { .repo = the_repository };
 
 	init_revisions(&rev, NULL);
 	copy_pathspec(&rev.prune_data, ps);
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 591d659faea..fd66fb4c165 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -923,7 +923,7 @@ static int unlock_worktree(int ac, const char **av, const char *prefix)
 
 static void validate_no_submodules(const struct worktree *wt)
 {
-	struct index_state istate = { NULL };
+	struct index_state istate = { .repo = the_repository };
 	struct strbuf path = STRBUF_INIT;
 	int i, found_submodules = 0;
 
diff --git a/fsmonitor-settings.c b/fsmonitor-settings.c
index ee63a97dc51..899bfe9c813 100644
--- a/fsmonitor-settings.c
+++ b/fsmonitor-settings.c
@@ -143,8 +143,6 @@ static void lookup_fsmonitor_settings(struct repository *r)
 
 enum fsmonitor_mode fsm_settings__get_mode(struct repository *r)
 {
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		lookup_fsmonitor_settings(r);
 
@@ -153,8 +151,6 @@ enum fsmonitor_mode fsm_settings__get_mode(struct repository *r)
 
 const char *fsm_settings__get_hook_path(struct repository *r)
 {
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		lookup_fsmonitor_settings(r);
 
@@ -174,8 +170,6 @@ void fsm_settings__set_ipc(struct repository *r)
 	 * Caller requested IPC explicitly, so avoid (possibly
 	 * recursive) config lookup.
 	 */
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		r->settings.fsmonitor = alloc_settings();
 
@@ -197,8 +191,6 @@ void fsm_settings__set_hook(struct repository *r, const char *path)
 	 * Caller requested hook explicitly, so avoid (possibly
 	 * recursive) config lookup.
 	 */
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		r->settings.fsmonitor = alloc_settings();
 
@@ -210,8 +202,6 @@ void fsm_settings__set_hook(struct repository *r, const char *path)
 
 void fsm_settings__set_disabled(struct repository *r)
 {
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		r->settings.fsmonitor = alloc_settings();
 
@@ -223,8 +213,6 @@ void fsm_settings__set_disabled(struct repository *r)
 void fsm_settings__set_incompatible(struct repository *r,
 				    enum fsmonitor_reason reason)
 {
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		r->settings.fsmonitor = alloc_settings();
 
@@ -235,8 +223,6 @@ void fsm_settings__set_incompatible(struct repository *r,
 
 enum fsmonitor_reason fsm_settings__get_reason(struct repository *r)
 {
-	if (!r)
-		r = the_repository;
 	if (!r->settings.fsmonitor)
 		lookup_fsmonitor_settings(r);
 
diff --git a/fsmonitor.c b/fsmonitor.c
index 08af00c7387..a5b9e75437b 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -304,7 +304,7 @@ void refresh_fsmonitor(struct index_state *istate)
 	char *buf;
 	unsigned int i;
 	int is_trivial = 0;
-	struct repository *r = istate->repo ? istate->repo : the_repository;
+	struct repository *r = istate->repo;
 	enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
 	enum fsmonitor_reason reason = fsm_settings__get_reason(r);
 
diff --git a/merge-recursive.c b/merge-recursive.c
index 2fd0aa96875..a63d2e330d5 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -412,7 +412,7 @@ static int unpack_trees_start(struct merge_options *opt,
 {
 	int rc;
 	struct tree_desc t[3];
-	struct index_state tmp_index = { NULL };
+	struct index_state tmp_index = { .repo = opt->repo };
 
 	memset(&opt->priv->unpack_opts, 0, sizeof(opt->priv->unpack_opts));
 	if (opt->priv->call_depth)
diff --git a/read-cache.c b/read-cache.c
index 78e38b0da28..3f018874926 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2300,8 +2300,6 @@ static void set_new_index_sparsity(struct index_state *istate)
 	 * If the index's repo exists, mark it sparse according to
 	 * repo settings.
 	 */
-	if (!istate->repo)
-		return;
 	prepare_repo_settings(istate->repo);
 	if (!istate->repo->settings.command_requires_full_index &&
 	    is_sparse_index_allowed(istate, 0))
@@ -2330,8 +2328,6 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	fd = open(path, O_RDONLY);
 	if (fd < 0) {
 		if (!must_exist && errno == ENOENT) {
-			if (!istate->repo)
-				istate->repo = the_repository;
 			set_new_index_sparsity(istate);
 			return 0;
 		}
@@ -2433,9 +2429,6 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	trace2_data_intmax("index", the_repository, "read/cache_nr",
 			   istate->cache_nr);
 
-	if (!istate->repo)
-		istate->repo = the_repository;
-
 	/*
 	 * If the command explicitly requires a full index, force it
 	 * to be full. Otherwise, correct the sparsity based on repository
@@ -2501,6 +2494,7 @@ int read_index_from(struct index_state *istate, const char *path,
 		discard_index(split_index->base);
 	else
 		CALLOC_ARRAY(split_index->base, 1);
+	split_index->base->repo = istate->repo;
 
 	base_oid_hex = oid_to_hex(&split_index->base_oid);
 	base_path = xstrfmt("%s/sharedindex.%s", gitdir, base_oid_hex);
@@ -2929,7 +2923,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
 	int ieot_entries = 1;
 	struct index_entry_offset_table *ieot = NULL;
 	int nr, nr_threads;
-	struct repository *r = istate->repo ? istate->repo : the_repository;
+	struct repository *r = istate->repo;
 
 	f = hashfd(tempfile->fd, tempfile->filename.buf);
 
diff --git a/repository.c b/repository.c
index 3427085fd6d..fdebc8c597c 100644
--- a/repository.c
+++ b/repository.c
@@ -28,6 +28,8 @@ void initialize_the_repository(void)
 	the_repo.remote_state = remote_state_new();
 	the_repo.parsed_objects = parsed_object_pool_new();
 
+	the_index.repo = the_repository;
+
 	repo_set_hash_algo(&the_repo, GIT_HASH_SHA1);
 }
 
diff --git a/revision.c b/revision.c
index 100e5ad5110..785be1eb3bf 100644
--- a/revision.c
+++ b/revision.c
@@ -1813,7 +1813,7 @@ void add_index_objects_to_pending(struct rev_info *revs, unsigned int flags)
 	worktrees = get_worktrees();
 	for (p = worktrees; *p; p++) {
 		struct worktree *wt = *p;
-		struct index_state istate = { NULL };
+		struct index_state istate = { .repo = revs->repo };
 
 		if (wt->is_current)
 			continue; /* current index already taken care of */
diff --git a/sparse-index.c b/sparse-index.c
index 86e3b99870b..147a13386a4 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;
 
 	/*
diff --git a/split-index.c b/split-index.c
index 9d0ccc30d00..7815ca9f33e 100644
--- a/split-index.c
+++ b/split-index.c
@@ -91,6 +91,7 @@ void move_cache_to_base_index(struct index_state *istate)
 	}
 
 	CALLOC_ARRAY(si->base, 1);
+	si->base->repo = istate->repo;
 	si->base->version = istate->version;
 	/* zero timestamp disables racy test in ce_write_index() */
 	si->base->timestamp = istate->timestamp;
diff --git a/unpack-trees.c b/unpack-trees.c
index 2381cd7cac4..e8f25bbdce7 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -1906,6 +1906,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	}
 
 	memset(&o->result, 0, sizeof(o->result));
+	o->result.repo = o->src_index->repo;
 	o->result.initialized = 1;
 	o->result.timestamp.sec = o->src_index->timestamp.sec;
 	o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-- 
2.39.0.1195.gabc92c078c4