Deploy versioned git_odb_backend structure

src/odb.c

@@ -363,12 +363,27 @@ int git_odb_new(git_odb **out)
 	return 0;
 }
 
+static bool backend_has_valid_version(git_odb_backend *backend)
+{
+	if (!backend)
+		return true;
+
+	if (backend->version > 0 && backend->version <= GIT_ODB_BACKEND_VERSION)
+		return true;
+
+	giterr_set(GITERR_INVALID, "Invalid version %d on git_odb_backend", backend->version);
+	return false;
+}
+
 static int add_backend_internal(git_odb *odb, git_odb_backend *backend, int priority, int is_alternate)
 {
 	backend_internal *internal;
 
 	assert(odb && backend);
 
+	if (!backend_has_valid_version(backend))
+		return -1;
+
 	/* Check if the backend is already owned by another ODB */
 	assert(!backend->odb || backend->odb == odb);
 

src/odb_loose.c

@@ -915,6 +915,7 @@ int git_odb_backend_loose(
 	backend = git__calloc(1, sizeof(loose_backend));
 	GITERR_CHECK_ALLOC(backend);
 
+	backend->parent.version = GIT_ODB_BACKEND_VERSION;
 	backend->objects_dir = git__strdup(objects_dir);
 	GITERR_CHECK_ALLOC(backend->objects_dir);
 

src/odb_pack.c

@@ -570,6 +570,7 @@ int git_odb_backend_one_pack(git_odb_backend **backend_out, const char *idx)
 
 	backend = git__calloc(1, sizeof(struct pack_backend));
 	GITERR_CHECK_ALLOC(backend);
+	backend->parent.version = GIT_ODB_BACKEND_VERSION;
 
 	if (git_vector_init(&backend->packs, 1, NULL) < 0)
 		goto on_error;
@@ -602,6 +603,7 @@ int git_odb_backend_pack(git_odb_backend **backend_out, const char *objects_dir)
 
 	backend = git__calloc(1, sizeof(struct pack_backend));
 	GITERR_CHECK_ALLOC(backend);
+	backend->parent.version = GIT_ODB_BACKEND_VERSION;
 
 	if (git_vector_init(&backend->packs, 8, packfile_sort__cb) < 0 ||
 		git_buf_joinpath(&path, objects_dir, "pack") < 0)

tests-clar/odb/sorting.c

@@ -11,11 +11,11 @@ static git_odb_backend *new_backend(int position)
 {
 	fake_backend *b;
 
-	b = git__malloc(sizeof(fake_backend));
+	b = git__calloc(1, sizeof(fake_backend));
 	if (b == NULL)
 		return NULL;
 
-	memset(b, 0x0, sizeof(fake_backend));
+	b->base.version = GIT_ODB_BACKEND_VERSION;
 	b->position = position;
 	return (git_odb_backend *)b;
 }