repository: initialize index in repo_init()

When Git starts, one of the first things it will do is to call
`initialize_the_repository()`. This function sets up both the global
`the_repository` and `the_index` variables as required. Part of that
setup is also to set `the_repository.index = &the_index` so that the
index can be accessed via the repository.

When calling `repo_init()` on a repository though we set the complete
struct to all-zeroes, which will also cause us to unset the `index`
pointer. And as we don't re-initialize the index in that function, we
will end up with a `NULL` pointer here.

This has been fine until now becaues this function is only used to
create a new repository. git-init(1) does not access the index at all
after initializing the repository, whereas git-checkout(1) only uses
`the_index` directly. We are about to remove `the_index` though, which
will uncover this partially-initialized repository structure.

Refactor the code and create a common `initialize_repository()` function
that gets called from `repo_init()` and `initialize_the_repository()`.
This function sets up both the repository and the index as required.
Like this, we can easily special-case when `repo_init()` gets called
with `the_repository`.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

repository.c

@@ -25,17 +25,20 @@ static struct repository the_repo;
 struct repository *the_repository;
 struct index_state the_index;
 
+static void initialize_repository(struct repository *repo,
+				  struct index_state *index)
+{
+	repo->index = index;
+	repo->objects = raw_object_store_new();
+	repo->remote_state = remote_state_new();
+	repo->parsed_objects = parsed_object_pool_new();
+	index_state_init(index, repo);
+}
+
 void initialize_the_repository(void)
 {
 	the_repository = &the_repo;
-
-	the_repo.index = &the_index;
-	the_repo.objects = raw_object_store_new();
-	the_repo.remote_state = remote_state_new();
-	the_repo.parsed_objects = parsed_object_pool_new();
-
-	index_state_init(&the_index, the_repository);
-
+	initialize_repository(the_repository, &the_index);
 	repo_set_hash_algo(&the_repo, GIT_HASH_SHA1);
 }
 
@@ -188,9 +191,12 @@ int repo_init(struct repository *repo,
 	struct repository_format format = REPOSITORY_FORMAT_INIT;
 	memset(repo, 0, sizeof(*repo));
 
-	repo->objects = raw_object_store_new();
-	repo->parsed_objects = parsed_object_pool_new();
-	repo->remote_state = remote_state_new();
+	if (repo == the_repository) {
+		initialize_repository(the_repository, &the_index);
+	} else {
+		ALLOC_ARRAY(repo->index, 1);
+		initialize_repository(repo, repo->index);
+	}
 
 	if (repo_init_gitdir(repo, gitdir))
 		goto error;