hash: provide per-algorithm null OIDs

Up until recently, object IDs did not have an algorithm member, only a
hash.  Consequently, it was possible to share one null (all-zeros)
object ID among all hash algorithms.  Now that we're going to be
handling objects from multiple hash algorithms, it's important to make
sure that all object IDs have a correct algorithm field.

Introduce a per-algorithm null OID, and add it to struct hash_algo.
Introduce a wrapper function as well, and use it everywhere we used to
use the null_oid constant.

Signed-off-by: brian m. carlson <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: bk2204

archive.c

@@ -275,9 +275,11 @@ int write_archive_entries(struct archiver_args *args,
 	int err;
 	struct strbuf path_in_archive = STRBUF_INIT;
 	struct strbuf content = STRBUF_INIT;
-	struct object_id fake_oid = null_oid;
+	struct object_id fake_oid;
 	int i;
 
+	oidcpy(&fake_oid, null_oid());
+
 	if (args->baselen > 0 && args->base[args->baselen - 1] == '/') {
 		size_t len = args->baselen;
 

blame.c

@@ -242,7 +242,7 @@ static struct commit *fake_working_tree_commit(struct repository *r,
 		switch (st.st_mode & S_IFMT) {
 		case S_IFREG:
 			if (opt->flags.allow_textconv &&
-			    textconv_object(r, read_from, mode, &null_oid, 0, &buf_ptr, &buf_len))
+			    textconv_object(r, read_from, mode, null_oid(), 0, &buf_ptr, &buf_len))
 				strbuf_attach(&buf, buf_ptr, buf_len, buf_len + 1);
 			else if (strbuf_read_file(&buf, read_from, st.st_size) != st.st_size)
 				die_errno("cannot open or read '%s'", read_from);

branch.c

@@ -322,7 +322,7 @@ void create_branch(struct repository *r,
 		transaction = ref_transaction_begin(&err);
 		if (!transaction ||
 		    ref_transaction_update(transaction, ref.buf,
-					   &oid, forcing ? NULL : &null_oid,
+					   &oid, forcing ? NULL : null_oid(),
 					   0, msg, &err) ||
 		    ref_transaction_commit(transaction, &err))
 			die("%s", err.buf);

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. */
@@ -638,7 +638,7 @@ 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);

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)) {

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",

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);

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()));
 	}
 }
 

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;

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;