Merge branch 'bc/hash-transition-interop-part-1'

SHA-256 transition.

* bc/hash-transition-interop-part-1:
  hex: print objects using the hash algorithm member
  hex: default to the_hash_algo on zero algorithm value
  builtin/pack-objects: avoid using struct object_id for pack hash
  commit-graph: don't store file hashes as struct object_id
  builtin/show-index: set the algorithm for object IDs
  hash: provide per-algorithm null OIDs
  hash: set, copy, and use algo field in struct object_id
  builtin/pack-redundant: avoid casting buffers to struct object_id
  Use the final_oid_fn to finalize hashing of object IDs
  hash: add a function to finalize object IDs
  http-push: set algorithm when reading object ID
  Always use oidread to read into struct object_id
  hash: add an algo member to struct object_id

17 files changed, 71 insertions, 67 deletions

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 4d19c35..0bf61e6 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -106,8 +106,8 @@ static int post_checkout_hook(struct commit *old_commit, struct commit *new_comm
 			      int changed)
 {
 	return run_hook_le(NULL, "post-checkout",
-			   oid_to_hex(old_commit ? &old_commit->object.oid : &null_oid),
-			   oid_to_hex(new_commit ? &new_commit->object.oid : &null_oid),
+			   oid_to_hex(old_commit ? &old_commit->object.oid : null_oid()),
+			   oid_to_hex(new_commit ? &new_commit->object.oid : null_oid()),
 			   changed ? "1" : "0", NULL);
 	/* "new_commit" can be NULL when checking out from the index before
 	   a commit exists. */
@@ -644,7 +644,7 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
 	opts.src_index = &the_index;
 	opts.dst_index = &the_index;
 	init_checkout_metadata(&opts.meta, info->refname,
-			       info->commit ? &info->commit->object.oid : &null_oid,
+			       info->commit ? &info->commit->object.oid : null_oid(),
 			       NULL);
 	parse_tree(tree);
 	init_tree_desc(&tree_desc, tree->buffer, tree->size);
diff --git a/builtin/clone.c b/builtin/clone.c
index f6b0c48..eeb74c0 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -820,7 +820,7 @@ static int checkout(int submodule_progress)
 	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
 		die(_("unable to write new index file"));
 
-	err |= run_hook_le(NULL, "post-checkout", oid_to_hex(&null_oid),
+	err |= run_hook_le(NULL, "post-checkout", oid_to_hex(null_oid()),
 			   oid_to_hex(&oid), "1", NULL);
 
 	if (!err && (option_recurse_submodules.nr > 0)) {
diff --git a/builtin/describe.c b/builtin/describe.c
index 40482d8..e912ba5 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -502,7 +502,7 @@ static void describe_blob(struct object_id oid, struct strbuf *dst)
 {
 	struct rev_info revs;
 	struct strvec args = STRVEC_INIT;
-	struct process_commit_data pcd = { null_oid, oid, dst, &revs};
+	struct process_commit_data pcd = { *null_oid(), oid, dst, &revs};
 
 	strvec_pushl(&args, "internal: The first arg is not parsed",
 		     "--objects", "--in-commit-order", "--reverse", "HEAD",
diff --git a/builtin/diff.c b/builtin/diff.c
index 617b9a4..2d87c37 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -98,7 +98,7 @@ static int builtin_diff_b_f(struct rev_info *revs,
 
 	stuff_change(&revs->diffopt,
 		     blob[0]->mode, canon_mode(st.st_mode),
-		     &blob[0]->item->oid, &null_oid,
+		     &blob[0]->item->oid, null_oid(),
 		     1, 0,
 		     blob[0]->path ? blob[0]->path : path,
 		     path);
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 85a76e0..3c20f16 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -870,7 +870,7 @@ static void handle_tag(const char *name, struct tag *tag)
 				p = rewrite_commit((struct commit *)tagged);
 				if (!p) {
 					printf("reset %s\nfrom %s\n\n",
-					       name, oid_to_hex(&null_oid));
+					       name, oid_to_hex(null_oid()));
 					free(buf);
 					return;
 				}
@@ -884,7 +884,7 @@ static void handle_tag(const char *name, struct tag *tag)
 
 	if (tagged->type == OBJ_TAG) {
 		printf("reset %s\nfrom %s\n\n",
-		       name, oid_to_hex(&null_oid));
+		       name, oid_to_hex(null_oid()));
 	}
 	skip_prefix(name, "refs/tags/", &name);
 	printf("tag %s\n", name);
@@ -1016,7 +1016,7 @@ static void handle_tags_and_duplicates(struct string_list *extras)
 				 * it.
 				 */
 				printf("reset %s\nfrom %s\n\n",
-				       name, oid_to_hex(&null_oid));
+				       name, oid_to_hex(null_oid()));
 				continue;
 			}
 
@@ -1035,7 +1035,7 @@ static void handle_tags_and_duplicates(struct string_list *extras)
 				if (!reference_excluded_commits) {
 					/* delete the ref */
 					printf("reset %s\nfrom %s\n\n",
-					       name, oid_to_hex(&null_oid));
+					       name, oid_to_hex(null_oid()));
 					continue;
 				}
 				/* set ref to commit using oid, not mark */
@@ -1146,7 +1146,7 @@ static void handle_deletes(void)
 			continue;
 
 		printf("reset %s\nfrom %s\n\n",
-				refspec->dst, oid_to_hex(&null_oid));
+				refspec->dst, oid_to_hex(null_oid()));
 	}
 }
 
diff --git a/builtin/fast-import.c b/builtin/fast-import.c
index 3afa81c..20406f6 100644
--- a/builtin/fast-import.c
+++ b/builtin/fast-import.c
@@ -940,7 +940,7 @@ static int store_object(
 	the_hash_algo->init_fn(&c);
 	the_hash_algo->update_fn(&c, hdr, hdrlen);
 	the_hash_algo->update_fn(&c, dat->buf, dat->len);
-	the_hash_algo->final_fn(oid.hash, &c);
+	the_hash_algo->final_oid_fn(&oid, &c);
 	if (oidout)
 		oidcpy(oidout, &oid);
 
@@ -1136,7 +1136,7 @@ static void stream_blob(uintmax_t len, struct object_id *oidout, uintmax_t mark)
 		}
 	}
 	git_deflate_end(&s);
-	the_hash_algo->final_fn(oid.hash, &c);
+	the_hash_algo->final_oid_fn(&oid, &c);
 
 	if (oidout)
 		oidcpy(oidout, &oid);
@@ -1276,8 +1276,8 @@ static void load_tree(struct tree_entry *root)
 		e->versions[0].mode = e->versions[1].mode;
 		e->name = to_atom(c, strlen(c));
 		c += e->name->str_len + 1;
-		hashcpy(e->versions[0].oid.hash, (unsigned char *)c);
-		hashcpy(e->versions[1].oid.hash, (unsigned char *)c);
+		oidread(&e->versions[0].oid, (unsigned char *)c);
+		oidread(&e->versions[1].oid, (unsigned char *)c);
 		c += the_hash_algo->rawsz;
 	}
 	free(buf);
diff --git a/builtin/grep.c b/builtin/grep.c
index b71b4a2..ab8822e 100644
--- a/builtin/grep.c
+++ b/builtin/grep.c
@@ -421,7 +421,7 @@ static int grep_submodule(struct grep_opt *opt,
 	struct grep_opt subopt;
 	int hit;
 
-	sub = submodule_from_path(superproject, &null_oid, path);
+	sub = submodule_from_path(superproject, null_oid(), path);
 
 	if (!is_submodule_active(superproject, path))
 		return 0;
diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 15507b5..3fbc5d7 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -489,7 +489,7 @@ static void *unpack_entry_data(off_t offset, unsigned long size,
 		bad_object(offset, _("inflate returned %d"), status);
 	git_inflate_end(&stream);
 	if (oid)
-		the_hash_algo->final_fn(oid->hash, &c);
+		the_hash_algo->final_oid_fn(oid, &c);
 	return buf == fixed_buf ? NULL : buf;
 }
 
@@ -524,7 +524,7 @@ static void *unpack_raw_entry(struct object_entry *obj,
 
 	switch (obj->type) {
 	case OBJ_REF_DELTA:
-		hashcpy(ref_oid->hash, fill(the_hash_algo->rawsz));
+		oidread(ref_oid, fill(the_hash_algo->rawsz));
 		use(the_hash_algo->rawsz);
 		break;
 	case OBJ_OFS_DELTA:
@@ -1358,7 +1358,7 @@ static struct object_entry *append_obj_to_pack(struct hashfile *f,
 	obj[1].idx.offset += write_compressed(f, buf, size);
 	obj[0].idx.crc32 = crc32_end(f);
 	hashflush(f);
-	hashcpy(obj->idx.oid.hash, sha1);
+	oidread(&obj->idx.oid, sha1);
 	return obj;
 }
 
diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index ecaca5e..844c7f4 100644
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -210,7 +210,7 @@ static void show_submodule(struct repository *superproject,
 {
 	struct repository subrepo;
 	const struct submodule *sub = submodule_from_path(superproject,
-							  &null_oid, path);
+							  null_oid(), path);
 
 	if (repo_submodule_init(&subrepo, superproject, sub))
 		return;
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index a050911..14bf700 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1030,7 +1030,7 @@ static void write_pack_file(void)
 	write_order = compute_write_order();
 
 	do {
-		struct object_id oid;
+		unsigned char hash[GIT_MAX_RAWSZ];
 		char *pack_tmp_name = NULL;
 
 		if (pack_to_stdout)
@@ -1059,13 +1059,13 @@ static void write_pack_file(void)
 		 * If so, rewrite it like in fast-import
 		 */
 		if (pack_to_stdout) {
-			finalize_hashfile(f, oid.hash, CSUM_HASH_IN_STREAM | CSUM_CLOSE);
+			finalize_hashfile(f, hash, CSUM_HASH_IN_STREAM | CSUM_CLOSE);
 		} else if (nr_written == nr_remaining) {
-			finalize_hashfile(f, oid.hash, CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
+			finalize_hashfile(f, hash, CSUM_HASH_IN_STREAM | CSUM_FSYNC | CSUM_CLOSE);
 		} else {
-			int fd = finalize_hashfile(f, oid.hash, 0);
-			fixup_pack_header_footer(fd, oid.hash, pack_tmp_name,
-						 nr_written, oid.hash, offset);
+			int fd = finalize_hashfile(f, hash, 0);
+			fixup_pack_header_footer(fd, hash, pack_tmp_name,
+						 nr_written, hash, offset);
 			close(fd);
 			if (write_bitmap_index) {
 				if (write_bitmap_index != WRITE_BITMAP_QUIET)
@@ -1100,17 +1100,17 @@ static void write_pack_file(void)
 			strbuf_addf(&tmpname, "%s-", base_name);
 
 			if (write_bitmap_index) {
-				bitmap_writer_set_checksum(oid.hash);
+				bitmap_writer_set_checksum(hash);
 				bitmap_writer_build_type_index(
 					&to_pack, written_list, nr_written);
 			}
 
 			finish_tmp_packfile(&tmpname, pack_tmp_name,
 					    written_list, nr_written,
-					    &pack_idx_opts, oid.hash);
+					    &pack_idx_opts, hash);
 
 			if (write_bitmap_index) {
-				strbuf_addf(&tmpname, "%s.bitmap", oid_to_hex(&oid));
+				strbuf_addf(&tmpname, "%s.bitmap", hash_to_hex(hash));
 
 				stop_progress(&progress_state);
 
@@ -1124,7 +1124,7 @@ static void write_pack_file(void)
 
 			strbuf_release(&tmpname);
 			free(pack_tmp_name);
-			puts(oid_to_hex(&oid));
+			puts(hash_to_hex(hash));
 		}
 
 		/* mark written objects as written to previous pack */
diff --git a/builtin/pack-redundant.c b/builtin/pack-redundant.c
index 7102996..8bf5c0a 100644
--- a/builtin/pack-redundant.c
+++ b/builtin/pack-redundant.c
@@ -20,7 +20,7 @@ static int load_all_packs, verbose, alt_odb;
 
 struct llist_item {
 	struct llist_item *next;
-	const struct object_id *oid;
+	struct object_id oid;
 };
 static struct llist {
 	struct llist_item *front;
@@ -95,10 +95,10 @@ static struct llist * llist_copy(struct llist *list)
 
 static inline struct llist_item *llist_insert(struct llist *list,
 					      struct llist_item *after,
-					      const struct object_id *oid)
+					      const unsigned char *oid)
 {
 	struct llist_item *new_item = llist_item_get();
-	new_item->oid = oid;
+	oidread(&new_item->oid, oid);
 	new_item->next = NULL;
 
 	if (after != NULL) {
@@ -118,7 +118,7 @@ static inline struct llist_item *llist_insert(struct llist *list,
 }
 
 static inline struct llist_item *llist_insert_back(struct llist *list,
-						   const struct object_id *oid)
+						   const unsigned char *oid)
 {
 	return llist_insert(list, list->back, oid);
 }
@@ -130,9 +130,9 @@ static inline struct llist_item *llist_insert_sorted_unique(struct llist *list,
 
 	l = (hint == NULL) ? list->front : hint;
 	while (l) {
-		int cmp = oidcmp(l->oid, oid);
+		int cmp = oidcmp(&l->oid, oid);
 		if (cmp > 0) { /* we insert before this entry */
-			return llist_insert(list, prev, oid);
+			return llist_insert(list, prev, oid->hash);
 		}
 		if (!cmp) { /* already exists */
 			return l;
@@ -141,11 +141,11 @@ static inline struct llist_item *llist_insert_sorted_unique(struct llist *list,
 		l = l->next;
 	}
 	/* insert at the end */
-	return llist_insert_back(list, oid);
+	return llist_insert_back(list, oid->hash);
 }
 
 /* returns a pointer to an item in front of sha1 */
-static inline struct llist_item * llist_sorted_remove(struct llist *list, const struct object_id *oid, struct llist_item *hint)
+static inline struct llist_item * llist_sorted_remove(struct llist *list, const unsigned char *oid, struct llist_item *hint)
 {
 	struct llist_item *prev, *l;
 
@@ -153,7 +153,7 @@ redo_from_start:
 	l = (hint == NULL) ? list->front : hint;
 	prev = NULL;
 	while (l) {
-		const int cmp = oidcmp(l->oid, oid);
+		const int cmp = hashcmp(l->oid.hash, oid);
 		if (cmp > 0) /* not in list, since sorted */
 			return prev;
 		if (!cmp) { /* found */
@@ -188,7 +188,7 @@ static void llist_sorted_difference_inplace(struct llist *A,
 	b = B->front;
 
 	while (b) {
-		hint = llist_sorted_remove(A, b->oid, hint);
+		hint = llist_sorted_remove(A, b->oid.hash, hint);
 		b = b->next;
 	}
 }
@@ -260,10 +260,10 @@ static void cmp_two_packs(struct pack_list *p1, struct pack_list *p2)
 		/* cmp ~ p1 - p2 */
 		if (cmp == 0) {
 			p1_hint = llist_sorted_remove(p1->unique_objects,
-					(const struct object_id *)(p1_base + p1_off),
+					p1_base + p1_off,
 					p1_hint);
 			p2_hint = llist_sorted_remove(p2->unique_objects,
-					(const struct object_id *)(p1_base + p1_off),
+					p1_base + p1_off,
 					p2_hint);
 			p1_off += p1_step;
 			p2_off += p2_step;
@@ -455,7 +455,7 @@ static void load_all_objects(void)
 		l = pl->remaining_objects->front;
 		while (l) {
 			hint = llist_insert_sorted_unique(all_objects,
-							  l->oid, hint);
+							  &l->oid, hint);
 			l = l->next;
 		}
 		pl = pl->next;
@@ -521,7 +521,7 @@ static struct pack_list * add_pack(struct packed_git *p)
 	base += 256 * 4 + ((p->index_version < 2) ? 4 : 8);
 	step = the_hash_algo->rawsz + ((p->index_version < 2) ? 4 : 0);
 	while (off < p->num_objects * step) {
-		llist_insert_back(l.remaining_objects, (const struct object_id *)(base + off));
+		llist_insert_back(l.remaining_objects, base + off);
 		off += step;
 	}
 	l.all_objects_size = l.remaining_objects->size;
diff --git a/builtin/rebase.c b/builtin/rebase.c
index a756fba..12f0931 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -485,7 +485,7 @@ static const char * const builtin_rebase_interactive_usage[] = {
 int cmd_rebase__interactive(int argc, const char **argv, const char *prefix)
 {
 	struct rebase_options opts = REBASE_OPTIONS_INIT;
-	struct object_id squash_onto = null_oid;
+	struct object_id squash_onto = *null_oid();
 	enum action command = ACTION_NONE;
 	struct option options[] = {
 		OPT_NEGBIT(0, "ff", &opts.flags, N_("allow fast-forward"),
@@ -1140,7 +1140,7 @@ static int can_fast_forward(struct commit *onto, struct commit *upstream,
 
 	merge_bases = get_merge_bases(onto, head);
 	if (!merge_bases || merge_bases->next) {
-		oidcpy(merge_base, &null_oid);
+		oidcpy(merge_base, null_oid());
 		goto done;
 	}
 
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 6bc12c8..a347425 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -329,7 +329,7 @@ static void write_head_info(void)
 	for_each_alternate_ref(show_one_alternate_ref, &seen);
 	oidset_clear(&seen);
 	if (!sent_capabilities)
-		show_ref("capabilities^{}", &null_oid);
+		show_ref("capabilities^{}", null_oid());
 
 	advertise_shallow_grafts(1);
 
diff --git a/builtin/show-index.c b/builtin/show-index.c
index 8106b03..0e0b9fb 100644
--- a/builtin/show-index.c
+++ b/builtin/show-index.c
@@ -71,9 +71,11 @@ int cmd_show_index(int argc, const char **argv, const char *prefix)
 			uint32_t off;
 		} *entries;
 		ALLOC_ARRAY(entries, nr);
-		for (i = 0; i < nr; i++)
+		for (i = 0; i < nr; i++) {
 			if (fread(entries[i].oid.hash, hashsz, 1, stdin) != 1)
 				die("unable to read sha1 %u/%u", i, nr);
+			entries[i].oid.algo = hash_algo_by_ptr(the_hash_algo);
+		}
 		for (i = 0; i < nr; i++)
 			if (fread(&entries[i].crc, 4, 1, stdin) != 1)
 				die("unable to read crc %u/%u", i, nr);
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 9d505a6..d55f626 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -426,7 +426,8 @@ static int module_list(int argc, const char **argv, const char *prefix)
 		const struct cache_entry *ce = list.entries[i];
 
 		if (ce_stage(ce))
-			printf("%06o %s U\t", ce->ce_mode, oid_to_hex(&null_oid));
+			printf("%06o %s U\t", ce->ce_mode,
+			       oid_to_hex(null_oid()));
 		else
 			printf("%06o %s %d\t", ce->ce_mode,
 			       oid_to_hex(&ce->oid), ce_stage(ce));
@@ -466,7 +467,7 @@ static void runcommand_in_submodule_cb(const struct cache_entry *list_item,
 
 	displaypath = get_submodule_displaypath(path, info->prefix);
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 
 	if (!sub)
 		die(_("No url found for submodule path '%s' in .gitmodules"),
@@ -623,7 +624,7 @@ static void init_submodule(const char *path, const char *prefix,
 
 	displaypath = get_submodule_displaypath(path, prefix);
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 
 	if (!sub)
 		die(_("No url found for submodule path '%s' in .gitmodules"),
@@ -783,14 +784,14 @@ static void status_submodule(const char *path, const struct object_id *ce_oid,
 	struct strbuf buf = STRBUF_INIT;
 	const char *git_dir;
 
-	if (!submodule_from_path(the_repository, &null_oid, path))
+	if (!submodule_from_path(the_repository, null_oid(), path))
 		die(_("no submodule mapping found in .gitmodules for path '%s'"),
 		      path);
 
 	displaypath = get_submodule_displaypath(path, prefix);
 
 	if ((CE_STAGEMASK & ce_flags) >> CE_STAGESHIFT) {
-		print_status(flags, 'U', path, &null_oid, displaypath);
+		print_status(flags, 'U', path, null_oid(), displaypath);
 		goto cleanup;
 	}
 
@@ -916,7 +917,7 @@ static int module_name(int argc, const char **argv, const char *prefix)
 	if (argc != 2)
 		usage(_("git submodule--helper name <path>"));
 
-	sub = submodule_from_path(the_repository, &null_oid, argv[1]);
+	sub = submodule_from_path(the_repository, null_oid(), argv[1]);
 
 	if (!sub)
 		die(_("no submodule mapping found in .gitmodules for path '%s'"),
@@ -1040,7 +1041,7 @@ static void generate_submodule_summary(struct summary_cb *info,
 	char *errmsg = NULL;
 	int total_commits = -1;
 
-	if (!info->cached && oideq(&p->oid_dst, &null_oid)) {
+	if (!info->cached && oideq(&p->oid_dst, null_oid())) {
 		if (S_ISGITLINK(p->mod_dst)) {
 			struct ref_store *refs = get_submodule_ref_store(p->sm_path);
 			if (refs)
@@ -1177,7 +1178,7 @@ static void prepare_submodule_summary(struct summary_cb *info,
 
 		if (info->for_status && p->status != 'A' &&
 		    (sub = submodule_from_path(the_repository,
-					       &null_oid, p->sm_path))) {
+					       null_oid(), p->sm_path))) {
 			char *config_key = NULL;
 			const char *value;
 			int ignore_all = 0;
@@ -1373,7 +1374,7 @@ static void sync_submodule(const char *path, const char *prefix,
 	if (!is_submodule_active(the_repository, path))
 		return;
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 
 	if (sub && sub->url) {
 		if (starts_with_dot_dot_slash(sub->url) ||
@@ -1525,7 +1526,7 @@ static void deinit_submodule(const char *path, const char *prefix,
 	struct strbuf sb_config = STRBUF_INIT;
 	char *sub_git_dir = xstrfmt("%s/.git", path);
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 
 	if (!sub || !sub->name)
 		goto cleanup;
@@ -1925,7 +1926,7 @@ static void determine_submodule_update_strategy(struct repository *r,
 						const char *update,
 						struct submodule_update_strategy *out)
 {
-	const struct submodule *sub = submodule_from_path(r, &null_oid, path);
+	const struct submodule *sub = submodule_from_path(r, null_oid(), path);
 	char *key;
 	const char *val;
 
@@ -2077,7 +2078,7 @@ static int prepare_to_clone_next_submodule(const struct cache_entry *ce,
 		goto cleanup;
 	}
 
-	sub = submodule_from_path(the_repository, &null_oid, ce->name);
+	sub = submodule_from_path(the_repository, null_oid(), ce->name);
 
 	if (suc->recursive_prefix)
 		displaypath = relative_path(suc->recursive_prefix,
@@ -2395,7 +2396,7 @@ static const char *remote_submodule_branch(const char *path)
 	const char *branch = NULL;
 	char *key;
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 	if (!sub)
 		return NULL;
 
@@ -2533,7 +2534,7 @@ static int ensure_core_worktree(int argc, const char **argv, const char *prefix)
 
 	path = argv[1];
 
-	sub = submodule_from_path(the_repository, &null_oid, path);
+	sub = submodule_from_path(the_repository, null_oid(), path);
 	if (!sub)
 		BUG("We could get the submodule handle before?");
 
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 4a70b17..4a94662 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -355,7 +355,7 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 	struct object_id base_oid;
 
 	if (type == OBJ_REF_DELTA) {
-		hashcpy(base_oid.hash, fill(the_hash_algo->rawsz));
+		oidread(&base_oid, fill(the_hash_algo->rawsz));
 		use(the_hash_algo->rawsz);
 		delta_data = get_data(delta_size);
 		if (dry_run || !delta_data) {
@@ -421,7 +421,8 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 			 * has not been resolved yet.
 			 */
 			oidclr(&obj_list[nr].oid);
-			add_delta_to_list(nr, &null_oid, base_offset, delta_data, delta_size);
+			add_delta_to_list(nr, null_oid(), base_offset,
+					  delta_data, delta_size);
 			return;
 		}
 	}
@@ -576,7 +577,7 @@ int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
 	the_hash_algo->init_fn(&ctx);
 	unpack_all();
 	the_hash_algo->update_fn(&ctx, buffer, offset);
-	the_hash_algo->final_fn(oid.hash, &ctx);
+	the_hash_algo->final_oid_fn(&oid, &ctx);
 	if (strict) {
 		write_rest();
 		if (fsck_finish(&fsck_options))
diff --git a/builtin/worktree.c b/builtin/worktree.c
index 8771453..f754978 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -331,7 +331,7 @@ static int add_worktree(const char *path, const char *refname,
 	 */
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
-	write_file(sb.buf, "%s", oid_to_hex(&null_oid));
+	write_file(sb.buf, "%s", oid_to_hex(null_oid()));
 	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
 	write_file(sb.buf, "../..");
@@ -394,7 +394,7 @@ done:
 			cp.argv = NULL;
 			cp.trace2_hook_name = "post-checkout";
 			strvec_pushl(&cp.args, absolute_path(hook),
-				     oid_to_hex(&null_oid),
+				     oid_to_hex(null_oid()),
 				     oid_to_hex(&commit->object.oid),
 				     "1", NULL);
 			ret = run_command(&cp);