Switch empty tree and blob lookups to use hash abstraction

Switch the uses of empty_tree_oid and empty_blob_oid to use the
current_hash abstraction that represents the current hash algorithm in
use.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -1433,7 +1433,7 @@ static void write_index_patch(const struct am_state *state)
 	if (!get_oid_tree("HEAD", &head))
 		tree = lookup_tree(&head);
 	else
-		tree = lookup_tree(&empty_tree_oid);
+		tree = lookup_tree(the_hash_algo->empty_tree);
 
 	fp = xfopen(am_path(state, "patch"), "w");
 	init_revisions(&rev_info, NULL);

builtin/checkout.c

@@ -514,7 +514,7 @@ static int merge_working_tree(const struct checkout_opts *opts,
 		}
 		tree = parse_tree_indirect(old->commit ?
 					   &old->commit->object.oid :
-					   &empty_tree_oid);
+					   the_hash_algo->empty_tree);
 		init_tree_desc(&trees[0], tree->buffer, tree->size);
 		tree = parse_tree_indirect(&new->commit->object.oid);
 		init_tree_desc(&trees[1], tree->buffer, tree->size);

builtin/diff.c

@@ -379,7 +379,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 				add_head_to_pending(&rev);
 				if (!rev.pending.nr) {
 					struct tree *tree;
-					tree = lookup_tree(&empty_tree_oid);
+					tree = lookup_tree(the_hash_algo->empty_tree);
 					add_pending_object(&rev, &tree->object, "HEAD");
 				}
 				break;

builtin/pull.c

@@ -545,7 +545,7 @@ static int pull_into_void(const struct object_id *merge_head,
 	 * index/worktree changes that the user already made on the unborn
 	 * branch.
 	 */
-	if (checkout_fast_forward(&empty_tree_oid, merge_head, 0))
+	if (checkout_fast_forward(the_hash_algo->empty_tree, merge_head, 0))
 		return 1;
 
 	if (update_ref("initial pull", "HEAD", merge_head, curr_head, 0, UPDATE_REFS_DIE_ON_ERR))

cache.h

@@ -1024,22 +1024,22 @@ extern const struct object_id empty_blob_oid;
 
 static inline int is_empty_blob_sha1(const unsigned char *sha1)
 {
-	return !hashcmp(sha1, EMPTY_BLOB_SHA1_BIN);
+	return !hashcmp(sha1, the_hash_algo->empty_blob->hash);
 }
 
 static inline int is_empty_blob_oid(const struct object_id *oid)
 {
-	return !hashcmp(oid->hash, EMPTY_BLOB_SHA1_BIN);
+	return !oidcmp(oid, the_hash_algo->empty_blob);
 }
 
 static inline int is_empty_tree_sha1(const unsigned char *sha1)
 {
-	return !hashcmp(sha1, EMPTY_TREE_SHA1_BIN);
+	return !hashcmp(sha1, the_hash_algo->empty_tree->hash);
 }
 
 static inline int is_empty_tree_oid(const struct object_id *oid)
 {
-	return !hashcmp(oid->hash, EMPTY_TREE_SHA1_BIN);
+	return !oidcmp(oid, the_hash_algo->empty_tree);
 }
 
 /* set default permissions by passing mode arguments to open(2) */

diff-lib.c

@@ -217,7 +217,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
 			} else if (revs->diffopt.ita_invisible_in_index &&
 				   ce_intent_to_add(ce)) {
 				diff_addremove(&revs->diffopt, '+', ce->ce_mode,
-					       &empty_tree_oid, 0,
+					       the_hash_algo->empty_tree, 0,
 					       ce->name, 0);
 				continue;
 			}

merge-recursive.c

@@ -2081,7 +2081,7 @@ int merge_recursive(struct merge_options *o,
 		/* if there is no common ancestor, use an empty tree */
 		struct tree *tree;
 
-		tree = lookup_tree(&empty_tree_oid);
+		tree = lookup_tree(the_hash_algo->empty_tree);
 		merged_common_ancestors = make_virtual_commit(tree, "ancestor");
 	}
 

notes-merge.c

@@ -595,7 +595,7 @@ int notes_merge(struct notes_merge_options *o,
 	bases = get_merge_bases(local, remote);
 	if (!bases) {
 		base_oid = &null_oid;
-		base_tree_oid = &empty_tree_oid;
+		base_tree_oid = the_hash_algo->empty_tree;
 		if (o->verbosity >= 4)
 			printf("No merge base found; doing history-less merge\n");
 	} else if (!bases->next) {

sequencer.c

@@ -347,7 +347,7 @@ static int read_oneliner(struct strbuf *buf,
 
 static struct tree *empty_tree(void)
 {
-	return lookup_tree(&empty_tree_oid);
+	return lookup_tree(the_hash_algo->empty_tree);
 }
 
 static int error_dirty_index(struct replay_opts *opts)
@@ -705,7 +705,7 @@ static int is_original_commit_empty(struct commit *commit)
 				oid_to_hex(&parent->object.oid));
 		ptree_oid = &parent->tree->object.oid;
 	} else {
-		ptree_oid = &empty_tree_oid; /* commit is root */
+		ptree_oid = the_hash_algo->empty_tree; /* commit is root */
 	}
 
 	return !oidcmp(ptree_oid, &commit->tree->object.oid);
@@ -958,7 +958,7 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
 	} else {
 		unborn = get_oid("HEAD", &head);
 		if (unborn)
-			oidcpy(&head, &empty_tree_oid);
+			oidcpy(&head, the_hash_algo->empty_tree);
 		if (index_differs_from(unborn ? EMPTY_TREE_SHA1_HEX : "HEAD",
 				       NULL, 0))
 			return error_dirty_index(opts);

submodule.c

@@ -587,7 +587,7 @@ void show_submodule_inline_diff(struct diff_options *o, const char *path,
 		struct object_id *one, struct object_id *two,
 		unsigned dirty_submodule)
 {
-	const struct object_id *old = &empty_tree_oid, *new = &empty_tree_oid;
+	const struct object_id *old = the_hash_algo->empty_tree, *new = the_hash_algo->empty_tree;
 	struct commit *left = NULL, *right = NULL;
 	struct commit_list *merge_bases = NULL;
 	struct child_process cp = CHILD_PROCESS_INIT;