Merge branch 'bc/cocci'

Conversion from unsigned char sha1[20] to struct object_id
continues.

* bc/cocci:
  diff: convert prep_temp_blob() to struct object_id
  merge-recursive: convert merge_recursive_generic() to object_id
  merge-recursive: convert leaf functions to use struct object_id
  merge-recursive: convert struct merge_file_info to object_id
  merge-recursive: convert struct stage_data to use object_id
  diff: rename struct diff_filespec's sha1_valid member
  diff: convert struct diff_filespec to struct object_id
  coccinelle: apply object_id Coccinelle transformations
  coccinelle: convert hashcpy() with null_sha1 to hashclr()
  contrib/coccinelle: add basic Coccinelle transforms
  hex: add oid_to_hex_r()

25 files changed, 403 insertions, 283 deletions

diff --git a/bisect.c b/bisect.c
index b2a75c60cf..47cccdfb0d 100644
--- a/bisect.c
+++ b/bisect.c
@@ -754,7 +754,7 @@ static void handle_bad_merge_base(void)
 static void handle_skipped_merge_base(const unsigned char *mb)
 {
 	char *mb_hex = sha1_to_hex(mb);
-	char *bad_hex = sha1_to_hex(current_bad_oid->hash);
+	char *bad_hex = oid_to_hex(current_bad_oid);
 	char *good_hex = join_sha1_array_hex(&good_revs, ' ');
 
 	warning(_("the merge base between %s and [%s] "
diff --git a/builtin/blame.c b/builtin/blame.c
index 2ed83e16b6..8fec0e1fb3 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -598,7 +598,7 @@ static struct origin *find_origin(struct scoreboard *sb,
 			    p->status);
 		case 'M':
 			porigin = get_origin(sb, parent, origin->path);
-			hashcpy(porigin->blob_sha1, p->one->sha1);
+			hashcpy(porigin->blob_sha1, p->one->oid.hash);
 			porigin->mode = p->one->mode;
 			break;
 		case 'A':
@@ -644,7 +644,7 @@ static struct origin *find_rename(struct scoreboard *sb,
 		if ((p->status == 'R' || p->status == 'C') &&
 		    !strcmp(p->two->path, origin->path)) {
 			porigin = get_origin(sb, parent, p->one->path);
-			hashcpy(porigin->blob_sha1, p->one->sha1);
+			hashcpy(porigin->blob_sha1, p->one->oid.hash);
 			porigin->mode = p->one->mode;
 			break;
 		}
@@ -1308,7 +1308,7 @@ static void find_copy_in_parent(struct scoreboard *sb,
 				continue;
 
 			norigin = get_origin(sb, parent, p->one->path);
-			hashcpy(norigin->blob_sha1, p->one->sha1);
+			hashcpy(norigin->blob_sha1, p->one->oid.hash);
 			norigin->mode = p->one->mode;
 			fill_origin_blob(&sb->revs->diffopt, norigin, &file_p);
 			if (!file_p.ptr)
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 8164b581a6..c0652a7ed0 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -368,7 +368,7 @@ static void show_filemodify(struct diff_queue_struct *q,
 			print_path(spec->path);
 			putchar('\n');
 
-			if (!hashcmp(ospec->sha1, spec->sha1) &&
+			if (!oidcmp(&ospec->oid, &spec->oid) &&
 			    ospec->mode == spec->mode)
 				break;
 			/* fallthrough */
@@ -383,10 +383,10 @@ static void show_filemodify(struct diff_queue_struct *q,
 			if (no_data || S_ISGITLINK(spec->mode))
 				printf("M %06o %s ", spec->mode,
 				       sha1_to_hex(anonymize ?
-						   anonymize_sha1(spec->sha1) :
-						   spec->sha1));
+						   anonymize_sha1(spec->oid.hash) :
+						   spec->oid.hash));
 			else {
-				struct object *object = lookup_object(spec->sha1);
+				struct object *object = lookup_object(spec->oid.hash);
 				printf("M %06o :%d ", spec->mode,
 				       get_object_mark(object));
 			}
@@ -572,7 +572,7 @@ static void handle_commit(struct commit *commit, struct rev_info *rev)
 	/* Export the referenced blobs, and remember the marks. */
 	for (i = 0; i < diff_queued_diff.nr; i++)
 		if (!S_ISGITLINK(diff_queued_diff.queue[i]->two->mode))
-			export_blob(diff_queued_diff.queue[i]->two->sha1);
+			export_blob(diff_queued_diff.queue[i]->two->oid.hash);
 
 	refname = commit->util;
 	if (anonymize) {
diff --git a/builtin/merge-recursive.c b/builtin/merge-recursive.c
index 491efd556e..fd2c4556e1 100644
--- a/builtin/merge-recursive.c
+++ b/builtin/merge-recursive.c
@@ -9,10 +9,10 @@ static const char builtin_merge_recursive_usage[] =
 
 static const char *better_branch_name(const char *branch)
 {
-	static char githead_env[8 + 40 + 1];
+	static char githead_env[8 + GIT_SHA1_HEXSZ + 1];
 	char *name;
 
-	if (strlen(branch) != 40)
+	if (strlen(branch) != GIT_SHA1_HEXSZ)
 		return branch;
 	xsnprintf(githead_env, sizeof(githead_env), "GITHEAD_%s", branch);
 	name = getenv(githead_env);
@@ -21,10 +21,10 @@ static const char *better_branch_name(const char *branch)
 
 int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 {
-	const unsigned char *bases[21];
+	const struct object_id *bases[21];
 	unsigned bases_count = 0;
 	int i, failed;
-	unsigned char h1[20], h2[20];
+	struct object_id h1, h2;
 	struct merge_options o;
 	struct commit *result;
 
@@ -46,10 +46,10 @@ int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 		if (bases_count < ARRAY_SIZE(bases)-1) {
-			unsigned char *sha = xmalloc(20);
-			if (get_sha1(argv[i], sha))
+			struct object_id *oid = xmalloc(sizeof(struct object_id));
+			if (get_oid(argv[i], oid))
 				die("Could not parse object '%s'", argv[i]);
-			bases[bases_count++] = sha;
+			bases[bases_count++] = oid;
 		}
 		else
 			warning("Cannot handle more than %d bases. "
@@ -62,9 +62,9 @@ int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 	o.branch1 = argv[++i];
 	o.branch2 = argv[++i];
 
-	if (get_sha1(o.branch1, h1))
+	if (get_oid(o.branch1, &h1))
 		die("Could not resolve ref '%s'", o.branch1);
-	if (get_sha1(o.branch2, h2))
+	if (get_oid(o.branch2, &h2))
 		die("Could not resolve ref '%s'", o.branch2);
 
 	o.branch1 = better_branch_name(o.branch1);
@@ -73,7 +73,7 @@ int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 	if (o.verbosity >= 3)
 		printf("Merging %s with %s\n", o.branch1, o.branch2);
 
-	failed = merge_recursive_generic(&o, h1, h2, bases_count, bases, &result);
+	failed = merge_recursive_generic(&o, &h1, &h2, bases_count, bases, &result);
 	if (failed < 0)
 		return 128; /* die() error code */
 	return failed;
diff --git a/builtin/merge.c b/builtin/merge.c
index d82f6c19a3..0dfe09eb19 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -501,7 +501,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		if (ref_exists(truname.buf)) {
 			strbuf_addf(msg,
 				    "%s\t\tbranch '%s'%s of .\n",
-				    sha1_to_hex(remote_head->object.oid.hash),
+				    oid_to_hex(&remote_head->object.oid),
 				    truname.buf + 11,
 				    (early ? " (early part)" : ""));
 			strbuf_release(&truname);
@@ -515,7 +515,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		desc = merge_remote_util(remote_head);
 		if (desc && desc->obj && desc->obj->type == OBJ_TAG) {
 			strbuf_addf(msg, "%s\t\t%s '%s'\n",
-				    sha1_to_hex(desc->obj->oid.hash),
+				    oid_to_hex(&desc->obj->oid),
 				    typename(desc->obj->type),
 				    remote);
 			goto cleanup;
@@ -523,7 +523,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 	}
 
 	strbuf_addf(msg, "%s\t\tcommit '%s'\n",
-		sha1_to_hex(remote_head->object.oid.hash), remote);
+		oid_to_hex(&remote_head->object.oid), remote);
 cleanup:
 	strbuf_release(&buf);
 	strbuf_release(&bname);
@@ -1366,7 +1366,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	for (p = remoteheads; p; p = p->next) {
 		struct commit *commit = p->item;
 		strbuf_addf(&buf, "GITHEAD_%s",
-			    sha1_to_hex(commit->object.oid.hash));
+			    oid_to_hex(&commit->object.oid));
 		setenv(buf.buf, merge_remote_util(commit)->name, 1);
 		strbuf_reset(&buf);
 		if (fast_forward != FF_ONLY &&
@@ -1425,7 +1425,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		goto done;
 	} else if (fast_forward != FF_NO && !remoteheads->next &&
 			!common->next &&
-			!hashcmp(common->item->object.oid.hash, head_commit->object.oid.hash)) {
+			!oidcmp(&common->item->object.oid, &head_commit->object.oid)) {
 		/* Again the most common case of merging one remote. */
 		struct strbuf msg = STRBUF_INIT;
 		struct commit *commit;
@@ -1499,8 +1499,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			 * HEAD^^" would be missed.
 			 */
 			common_one = get_merge_bases(head_commit, j->item);
-			if (hashcmp(common_one->item->object.oid.hash,
-				j->item->object.oid.hash)) {
+			if (oidcmp(&common_one->item->object.oid, &j->item->object.oid)) {
 				up_to_date = 0;
 				break;
 			}
@@ -1530,7 +1529,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	     * Stash away the local changes so that we can try more than one.
 	     */
 	    save_state(stash))
-		hashcpy(stash, null_sha1);
+		hashclr(stash);
 
 	for (i = 0; i < use_strategies_nr; i++) {
 		int ret;
diff --git a/builtin/reset.c b/builtin/reset.c
index 5c6206bc1c..9020ec66c8 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -121,7 +121,7 @@ static void update_index_from_diff(struct diff_queue_struct *q,
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filespec *one = q->queue[i]->one;
-		int is_missing = !(one->mode && !is_null_sha1(one->sha1));
+		int is_missing = !(one->mode && !is_null_oid(&one->oid));
 		struct cache_entry *ce;
 
 		if (is_missing && !intent_to_add) {
@@ -129,7 +129,7 @@ static void update_index_from_diff(struct diff_queue_struct *q,
 			continue;
 		}
 
-		ce = make_cache_entry(one->mode, one->sha1, one->path,
+		ce = make_cache_entry(one->mode, one->oid.hash, one->path,
 				      0, 0);
 		if (!ce)
 			die(_("make_cache_entry failed for path '%s'"),
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 875e7ed998..172470bf24 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,
 			return; /* we are done */
 		else {
 			/* cannot resolve yet --- queue it */
-			hashcpy(obj_list[nr].sha1, null_sha1);
+			hashclr(obj_list[nr].sha1);
 			add_delta_to_list(nr, base_sha1, 0, delta_data, delta_size);
 			return;
 		}
@@ -406,7 +406,7 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size,
 			 * The delta base object is itself a delta that
 			 * has not been resolved yet.
 			 */
-			hashcpy(obj_list[nr].sha1, null_sha1);
+			hashclr(obj_list[nr].sha1);
 			add_delta_to_list(nr, null_sha1, base_offset, delta_data, delta_size);
 			return;
 		}
diff --git a/cache.h b/cache.h
index f1dc289d06..a93d1b7f5d 100644
--- a/cache.h
+++ b/cache.h
@@ -1193,6 +1193,7 @@ extern int get_oid_hex(const char *hex, struct object_id *sha1);
  *   printf("%s -> %s", sha1_to_hex(one), sha1_to_hex(two));
  */
 extern char *sha1_to_hex_r(char *out, const unsigned char *sha1);
+extern char *oid_to_hex_r(char *out, const struct object_id *oid);
 extern char *sha1_to_hex(const unsigned char *sha1);	/* static buffer result! */
 extern char *oid_to_hex(const struct object_id *oid);	/* same static buffer as sha1_to_hex */
 
diff --git a/combine-diff.c b/combine-diff.c
index 5920df8b8d..8e2a577bdb 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -44,9 +44,9 @@ static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr,
 			memset(p->parent, 0,
 			       sizeof(p->parent[0]) * num_parent);
 
-			hashcpy(p->oid.hash, q->queue[i]->two->sha1);
+			oidcpy(&p->oid, &q->queue[i]->two->oid);
 			p->mode = q->queue[i]->two->mode;
-			hashcpy(p->parent[n].oid.hash, q->queue[i]->one->sha1);
+			oidcpy(&p->parent[n].oid, &q->queue[i]->one->oid);
 			p->parent[n].mode = q->queue[i]->one->mode;
 			p->parent[n].status = q->queue[i]->status;
 			*tail = p;
@@ -77,7 +77,7 @@ static struct combine_diff_path *intersect_paths(struct combine_diff_path *curr,
 			continue;
 		}
 
-		hashcpy(p->parent[n].oid.hash, q->queue[i]->one->sha1);
+		oidcpy(&p->parent[n].oid, &q->queue[i]->one->oid);
 		p->parent[n].mode = q->queue[i]->one->mode;
 		p->parent[n].status = q->queue[i]->status;
 
@@ -1268,16 +1268,16 @@ static struct diff_filepair *combined_pair(struct combine_diff_path *p,
 	for (i = 0; i < num_parent; i++) {
 		pair->one[i].path = p->path;
 		pair->one[i].mode = p->parent[i].mode;
-		hashcpy(pair->one[i].sha1, p->parent[i].oid.hash);
-		pair->one[i].sha1_valid = !is_null_oid(&p->parent[i].oid);
+		oidcpy(&pair->one[i].oid, &p->parent[i].oid);
+		pair->one[i].oid_valid = !is_null_oid(&p->parent[i].oid);
 		pair->one[i].has_more_entries = 1;
 	}
 	pair->one[num_parent - 1].has_more_entries = 0;
 
 	pair->two->path = p->path;
 	pair->two->mode = p->mode;
-	hashcpy(pair->two->sha1, p->oid.hash);
-	pair->two->sha1_valid = !is_null_oid(&p->oid);
+	oidcpy(&pair->two->oid, &p->oid);
+	pair->two->oid_valid = !is_null_oid(&p->oid);
 	return pair;
 }
 
diff --git a/contrib/coccinelle/README b/contrib/coccinelle/README
new file mode 100644
index 0000000000..9c2f8879c2
--- /dev/null
+++ b/contrib/coccinelle/README
@@ -0,0 +1,2 @@
+This directory provides examples of Coccinelle (http://coccinelle.lip6.fr/)
+semantic patches that might be useful to developers.
diff --git a/contrib/coccinelle/object_id.cocci b/contrib/coccinelle/object_id.cocci
new file mode 100644
index 0000000000..8ccdbb5666
--- /dev/null
+++ b/contrib/coccinelle/object_id.cocci
@@ -0,0 +1,95 @@
+@@
+expression E1;
+@@
+- is_null_sha1(E1.hash)
++ is_null_oid(&E1)
+
+@@
+expression E1;
+@@
+- is_null_sha1(E1->hash)
++ is_null_oid(E1)
+
+@@
+expression E1;
+@@
+- sha1_to_hex(E1.hash)
++ oid_to_hex(&E1)
+
+@@
+expression E1;
+@@
+- sha1_to_hex(E1->hash)
++ oid_to_hex(E1)
+
+@@
+expression E1;
+@@
+- sha1_to_hex_r(E1.hash)
++ oid_to_hex_r(&E1)
+
+@@
+expression E1;
+@@
+- sha1_to_hex_r(E1->hash)
++ oid_to_hex_r(E1)
+
+@@
+expression E1;
+@@
+- hashclr(E1.hash)
++ oidclr(&E1)
+
+@@
+expression E1;
+@@
+- hashclr(E1->hash)
++ oidclr(E1)
+
+@@
+expression E1, E2;
+@@
+- hashcmp(E1.hash, E2.hash)
++ oidcmp(&E1, &E2)
+
+@@
+expression E1, E2;
+@@
+- hashcmp(E1->hash, E2->hash)
++ oidcmp(E1, E2)
+
+@@
+expression E1, E2;
+@@
+- hashcmp(E1->hash, E2.hash)
++ oidcmp(E1, &E2)
+
+@@
+expression E1, E2;
+@@
+- hashcmp(E1.hash, E2->hash)
++ oidcmp(&E1, E2)
+
+@@
+expression E1, E2;
+@@
+- hashcpy(E1.hash, E2.hash)
++ oidcpy(&E1, &E2)
+
+@@
+expression E1, E2;
+@@
+- hashcpy(E1->hash, E2->hash)
++ oidcpy(E1, E2)
+
+@@
+expression E1, E2;
+@@
+- hashcpy(E1->hash, E2.hash)
++ oidcpy(E1, &E2)
+
+@@
+expression E1, E2;
+@@
+- hashcpy(E1.hash, E2->hash)
++ oidcpy(&E1, E2)
diff --git a/diff.c b/diff.c
index b66b9beabc..7d03419880 100644
--- a/diff.c
+++ b/diff.c
@@ -1933,8 +1933,8 @@ static void show_dirstat(struct diff_options *options)
 
 		name = p->two->path ? p->two->path : p->one->path;
 
-		if (p->one->sha1_valid && p->two->sha1_valid)
-			content_changed = hashcmp(p->one->sha1, p->two->sha1);
+		if (p->one->oid_valid && p->two->oid_valid)
+			content_changed = oidcmp(&p->one->oid, &p->two->oid);
 		else
 			content_changed = 1;
 
@@ -2306,7 +2306,8 @@ static void builtin_diff(const char *name_a,
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one->path ? one->path : two->path,
 				line_prefix,
-				one->sha1, two->sha1, two->dirty_submodule,
+				one->oid.hash, two->oid.hash,
+				two->dirty_submodule,
 				meta, del, add, reset);
 		return;
 	}
@@ -2384,7 +2385,7 @@ static void builtin_diff(const char *name_a,
 		if (!one->data && !two->data &&
 		    S_ISREG(one->mode) && S_ISREG(two->mode) &&
 		    !DIFF_OPT_TST(o, BINARY)) {
-			if (!hashcmp(one->sha1, two->sha1)) {
+			if (!oidcmp(&one->oid, &two->oid)) {
 				if (must_show_header)
 					fprintf(o->file, "%s", header.buf);
 				goto free_ab_and_return;
@@ -2505,7 +2506,7 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		return;
 	}
 
-	same_contents = !hashcmp(one->sha1, two->sha1);
+	same_contents = !oidcmp(&one->oid, &two->oid);
 
 	if (diff_filespec_is_binary(one) || diff_filespec_is_binary(two)) {
 		data->is_binary = 1;
@@ -2638,8 +2639,8 @@ void fill_filespec(struct diff_filespec *spec, const unsigned char *sha1,
 {
 	if (mode) {
 		spec->mode = canon_mode(mode);
-		hashcpy(spec->sha1, sha1);
-		spec->sha1_valid = sha1_valid;
+		hashcpy(spec->oid.hash, sha1);
+		spec->oid_valid = sha1_valid;
 	}
 }
 
@@ -2721,7 +2722,8 @@ static int diff_populate_gitlink(struct diff_filespec *s, int size_only)
 	if (s->dirty_submodule)
 		dirty = "-dirty";
 
-	strbuf_addf(&buf, "Subproject commit %s%s\n", sha1_to_hex(s->sha1), dirty);
+	strbuf_addf(&buf, "Subproject commit %s%s\n",
+		    oid_to_hex(&s->oid), dirty);
 	s->size = buf.len;
 	if (size_only) {
 		s->data = NULL;
@@ -2764,8 +2766,8 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
 	if (S_ISGITLINK(s->mode))
 		return diff_populate_gitlink(s, size_only);
 
-	if (!s->sha1_valid ||
-	    reuse_worktree_file(s->path, s->sha1, 0)) {
+	if (!s->oid_valid ||
+	    reuse_worktree_file(s->path, s->oid.hash, 0)) {
 		struct strbuf buf = STRBUF_INIT;
 		struct stat st;
 		int fd;
@@ -2822,9 +2824,10 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
 	else {
 		enum object_type type;
 		if (size_only || (flags & CHECK_BINARY)) {
-			type = sha1_object_info(s->sha1, &s->size);
+			type = sha1_object_info(s->oid.hash, &s->size);
 			if (type < 0)
-				die("unable to read %s", sha1_to_hex(s->sha1));
+				die("unable to read %s",
+				    oid_to_hex(&s->oid));
 			if (size_only)
 				return 0;
 			if (s->size > big_file_threshold && s->is_binary == -1) {
@@ -2832,9 +2835,9 @@ int diff_populate_filespec(struct diff_filespec *s, unsigned int flags)
 				return 0;
 			}
 		}
-		s->data = read_sha1_file(s->sha1, &type, &s->size);
+		s->data = read_sha1_file(s->oid.hash, &type, &s->size);
 		if (!s->data)
-			die("unable to read %s", sha1_to_hex(s->sha1));
+			die("unable to read %s", oid_to_hex(&s->oid));
 		s->should_free = 1;
 	}
 	return 0;
@@ -2863,7 +2866,7 @@ void diff_free_filespec_data(struct diff_filespec *s)
 static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
 			   void *blob,
 			   unsigned long size,
-			   const unsigned char *sha1,
+			   const struct object_id *oid,
 			   int mode)
 {
 	int fd;
@@ -2888,7 +2891,7 @@ static void prep_temp_blob(const char *path, struct diff_tempfile *temp,
 		die_errno("unable to write temp-file");
 	close_tempfile(&temp->tempfile);
 	temp->name = get_tempfile_path(&temp->tempfile);
-	sha1_to_hex_r(temp->hex, sha1);
+	oid_to_hex_r(temp->hex, oid);
 	xsnprintf(temp->mode, sizeof(temp->mode), "%06o", mode);
 	strbuf_release(&buf);
 	strbuf_release(&template);
@@ -2912,8 +2915,8 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 	}
 
 	if (!S_ISGITLINK(one->mode) &&
-	    (!one->sha1_valid ||
-	     reuse_worktree_file(name, one->sha1, 1))) {
+	    (!one->oid_valid ||
+	     reuse_worktree_file(name, one->oid.hash, 1))) {
 		struct stat st;
 		if (lstat(name, &st) < 0) {
 			if (errno == ENOENT)
@@ -2925,19 +2928,19 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 			if (strbuf_readlink(&sb, name, st.st_size) < 0)
 				die_errno("readlink(%s)", name);
 			prep_temp_blob(name, temp, sb.buf, sb.len,
-				       (one->sha1_valid ?
-					one->sha1 : null_sha1),
-				       (one->sha1_valid ?
+				       (one->oid_valid ?
+					&one->oid : &null_oid),
+				       (one->oid_valid ?
 					one->mode : S_IFLNK));
 			strbuf_release(&sb);
 		}
 		else {
 			/* we can borrow from the file in the work tree */
 			temp->name = name;
-			if (!one->sha1_valid)
+			if (!one->oid_valid)
 				sha1_to_hex_r(temp->hex, null_sha1);
 			else
-				sha1_to_hex_r(temp->hex, one->sha1);
+				sha1_to_hex_r(temp->hex, one->oid.hash);
 			/* Even though we may sometimes borrow the
 			 * contents from the work tree, we always want
 			 * one->mode.  mode is trustworthy even when
@@ -2952,7 +2955,7 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
 		if (diff_populate_filespec(one, 0))
 			die("cannot read data blob for %s", one->path);
 		prep_temp_blob(name, temp, one->data, one->size,
-			       one->sha1, one->mode);
+			       &one->oid, one->mode);
 	}
 	return temp;
 }
@@ -3065,7 +3068,7 @@ static void fill_metainfo(struct strbuf *msg,
 	default:
 		*must_show_header = 0;
 	}
-	if (one && two && hashcmp(one->sha1, two->sha1)) {
+	if (one && two && oidcmp(&one->oid, &two->oid)) {
 		int abbrev = DIFF_OPT_TST(o, FULL_INDEX) ? 40 : DEFAULT_ABBREV;
 
 		if (DIFF_OPT_TST(o, BINARY)) {
@@ -3075,8 +3078,8 @@ static void fill_metainfo(struct strbuf *msg,
 				abbrev = 40;
 		}
 		strbuf_addf(msg, "%s%sindex %s..", line_prefix, set,
-			    find_unique_abbrev(one->sha1, abbrev));
-		strbuf_addstr(msg, find_unique_abbrev(two->sha1, abbrev));
+			    find_unique_abbrev(one->oid.hash, abbrev));
+		strbuf_addstr(msg, find_unique_abbrev(two->oid.hash, abbrev));
 		if (one->mode == two->mode)
 			strbuf_addf(msg, " %06o", one->mode);
 		strbuf_addf(msg, "%s\n", reset);
@@ -3131,20 +3134,20 @@ static void run_diff_cmd(const char *pgm,
 static void diff_fill_sha1_info(struct diff_filespec *one)
 {
 	if (DIFF_FILE_VALID(one)) {
-		if (!one->sha1_valid) {
+		if (!one->oid_valid) {
 			struct stat st;
 			if (one->is_stdin) {
-				hashcpy(one->sha1, null_sha1);
+				oidclr(&one->oid);
 				return;
 			}
 			if (lstat(one->path, &st) < 0)
 				die_errno("stat '%s'", one->path);
-			if (index_path(one->sha1, one->path, &st, 0))
+			if (index_path(one->oid.hash, one->path, &st, 0))
 				die("cannot hash %s", one->path);
 		}
 	}
 	else
-		hashclr(one->sha1);
+		oidclr(&one->oid);
 }
 
 static void strip_prefix(int prefix_length, const char **namep, const char **otherp)
@@ -4120,8 +4123,9 @@ static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
 	fprintf(opt->file, "%s", diff_line_prefix(opt));
 	if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
 		fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,
-			diff_unique_abbrev(p->one->sha1, opt->abbrev));
-		fprintf(opt->file, "%s ", diff_unique_abbrev(p->two->sha1, opt->abbrev));
+			diff_unique_abbrev(p->one->oid.hash, opt->abbrev));
+		fprintf(opt->file, "%s ",
+			diff_unique_abbrev(p->two->oid.hash, opt->abbrev));
 	}
 	if (p->score) {
 		fprintf(opt->file, "%c%03d%c", p->status, similarity_index(p),
@@ -4170,11 +4174,11 @@ int diff_unmodified_pair(struct diff_filepair *p)
 	/* both are valid and point at the same path.  that is, we are
 	 * dealing with a change.
 	 */
-	if (one->sha1_valid && two->sha1_valid &&
-	    !hashcmp(one->sha1, two->sha1) &&
+	if (one->oid_valid && two->oid_valid &&
+	    !oidcmp(&one->oid, &two->oid) &&
 	    !one->dirty_submodule && !two->dirty_submodule)
 		return 1; /* no change */
-	if (!one->sha1_valid && !two->sha1_valid)
+	if (!one->oid_valid && !two->oid_valid)
 		return 1; /* both look at the same file on the filesystem. */
 	return 0;
 }
@@ -4235,7 +4239,7 @@ void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
 		s->path,
 		DIFF_FILE_VALID(s) ? "valid" : "invalid",
 		s->mode,
-		s->sha1_valid ? sha1_to_hex(s->sha1) : "");
+		s->oid_valid ? oid_to_hex(&s->oid) : "");
 	fprintf(stderr, "queue[%d] %s size %lu\n",
 		x, one ? one : "",
 		s->size);
@@ -4305,11 +4309,11 @@ static void diff_resolve_rename_copy(void)
 			else
 				p->status = DIFF_STATUS_RENAMED;
 		}
-		else if (hashcmp(p->one->sha1, p->two->sha1) ||
+		else if (oidcmp(&p->one->oid, &p->two->oid) ||
 			 p->one->mode != p->two->mode ||
 			 p->one->dirty_submodule ||
 			 p->two->dirty_submodule ||
-			 is_null_sha1(p->one->sha1))
+			 is_null_oid(&p->one->oid))
 			p->status = DIFF_STATUS_MODIFIED;
 		else {
 			/* This is a "no-change" entry and should not
@@ -4525,8 +4529,10 @@ static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
 
 		if (diff_filespec_is_binary(p->one) ||
 		    diff_filespec_is_binary(p->two)) {
-			git_SHA1_Update(&ctx, sha1_to_hex(p->one->sha1), 40);
-			git_SHA1_Update(&ctx, sha1_to_hex(p->two->sha1), 40);
+			git_SHA1_Update(&ctx, oid_to_hex(&p->one->oid),
+					40);
+			git_SHA1_Update(&ctx, oid_to_hex(&p->two->oid),
+					40);
 			continue;
 		}
 
@@ -4818,7 +4824,7 @@ static int diff_filespec_check_stat_unmatch(struct diff_filepair *p)
 	 */
 	if (!DIFF_FILE_VALID(p->one) || /* (1) */
 	    !DIFF_FILE_VALID(p->two) ||
-	    (p->one->sha1_valid && p->two->sha1_valid) ||
+	    (p->one->oid_valid && p->two->oid_valid) ||
 	    (p->one->mode != p->two->mode) ||
 	    diff_populate_filespec(p->one, CHECK_SIZE_ONLY) ||
 	    diff_populate_filespec(p->two, CHECK_SIZE_ONLY) ||
@@ -5114,8 +5120,9 @@ size_t fill_textconv(struct userdiff_driver *driver,
 	if (!driver->textconv)
 		die("BUG: fill_textconv called with non-textconv driver");
 
-	if (driver->textconv_cache && df->sha1_valid) {
-		*outbuf = notes_cache_get(driver->textconv_cache, df->sha1,
+	if (driver->textconv_cache && df->oid_valid) {
+		*outbuf = notes_cache_get(driver->textconv_cache,
+					  df->oid.hash,
 					  &size);
 		if (*outbuf)
 			return size;
@@ -5125,9 +5132,9 @@ size_t fill_textconv(struct userdiff_driver *driver,
 	if (!*outbuf)
 		die("unable to read files to diff");
 
-	if (driver->textconv_cache && df->sha1_valid) {
+	if (driver->textconv_cache && df->oid_valid) {
 		/* ignore errors, as we might be in a readonly repository */
-		notes_cache_put(driver->textconv_cache, df->sha1, *outbuf,
+		notes_cache_put(driver->textconv_cache, df->oid.hash, *outbuf,
 				size);
 		/*
 		 * we could save up changes and flush them all at the end,
diff --git a/diffcore-break.c b/diffcore-break.c
index 5473493e10..881a74f29e 100644
--- a/diffcore-break.c
+++ b/diffcore-break.c
@@ -57,8 +57,8 @@ static int should_break(struct diff_filespec *src,
 		return 1; /* even their types are different */
 	}
 
-	if (src->sha1_valid && dst->sha1_valid &&
-	    !hashcmp(src->sha1, dst->sha1))
+	if (src->oid_valid && dst->oid_valid &&
+	    !oidcmp(&src->oid, &dst->oid))
 		return 0; /* they are the same */
 
 	if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 7f03eb5a04..58ac0a531b 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -60,7 +60,8 @@ static int add_rename_dst(struct diff_filespec *two)
 		memmove(rename_dst + first + 1, rename_dst + first,
 			(rename_dst_nr - first - 1) * sizeof(*rename_dst));
 	rename_dst[first].two = alloc_filespec(two->path);
-	fill_filespec(rename_dst[first].two, two->sha1, two->sha1_valid, two->mode);
+	fill_filespec(rename_dst[first].two, two->oid.hash, two->oid_valid,
+		      two->mode);
 	rename_dst[first].pair = NULL;
 	return 0;
 }
@@ -260,12 +261,13 @@ struct file_similarity {
 
 static unsigned int hash_filespec(struct diff_filespec *filespec)
 {
-	if (!filespec->sha1_valid) {
+	if (!filespec->oid_valid) {
 		if (diff_populate_filespec(filespec, 0))
 			return 0;
-		hash_sha1_file(filespec->data, filespec->size, "blob", filespec->sha1);
+		hash_sha1_file(filespec->data, filespec->size, "blob",
+			       filespec->oid.hash);
 	}
-	return sha1hash(filespec->sha1);
+	return sha1hash(filespec->oid.hash);
 }
 
 static int find_identical_files(struct hashmap *srcs,
@@ -287,7 +289,7 @@ static int find_identical_files(struct hashmap *srcs,
 		struct diff_filespec *source = p->filespec;
 
 		/* False hash collision? */
-		if (hashcmp(source->sha1, target->sha1))
+		if (oidcmp(&source->oid, &target->oid))
 			continue;
 		/* Non-regular files? If so, the modes must match! */
 		if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
@@ -466,7 +468,7 @@ void diffcore_rename(struct diff_options *options)
 				 strcmp(options->single_follow, p->two->path))
 				continue; /* not interested */
 			else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
-				 is_empty_blob_sha1(p->two->sha1))
+				 is_empty_blob_sha1(p->two->oid.hash))
 				continue;
 			else if (add_rename_dst(p->two) < 0) {
 				warning("skipping rename detection, detected"
@@ -476,7 +478,7 @@ void diffcore_rename(struct diff_options *options)
 			}
 		}
 		else if (!DIFF_OPT_TST(options, RENAME_EMPTY) &&
-			 is_empty_blob_sha1(p->one->sha1))
+			 is_empty_blob_sha1(p->one->oid.hash))
 			continue;
 		else if (!DIFF_PAIR_UNMERGED(p) && !DIFF_FILE_VALID(p->two)) {
 			/*
diff --git a/diffcore.h b/diffcore.h
index 33ea2de348..c11b8465fc 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -25,7 +25,7 @@
 struct userdiff_driver;
 
 struct diff_filespec {
-	unsigned char sha1[20];
+	struct object_id oid;
 	char *path;
 	void *data;
 	void *cnt_data;
@@ -33,7 +33,7 @@ struct diff_filespec {
 	int count;               /* Reference count */
 	int rename_used;         /* Count of rename users */
 	unsigned short mode;	 /* file mode */
-	unsigned sha1_valid : 1; /* if true, use sha1 and trust mode;
+	unsigned oid_valid : 1;  /* if true, use oid and trust mode;
 				  * if false, use the name and read from
 				  * the filesystem.
 				  */
diff --git a/hex.c b/hex.c
index 0519f853b2..9619b67af0 100644
--- a/hex.c
+++ b/hex.c
@@ -77,6 +77,11 @@ char *sha1_to_hex_r(char *buffer, const unsigned char *sha1)
 	return buffer;
 }
 
+char *oid_to_hex_r(char *buffer, const struct object_id *oid)
+{
+	return sha1_to_hex_r(buffer, oid->hash);
+}
+
 char *sha1_to_hex(const unsigned char *sha1)
 {
 	static int bufno;
diff --git a/line-log.c b/line-log.c
index a30c89a309..916e724870 100644
--- a/line-log.c
+++ b/line-log.c
@@ -519,7 +519,7 @@ static void fill_line_ends(struct diff_filespec *spec, long *lines,
 	char *data = NULL;
 
 	if (diff_populate_filespec(spec, 0))
-		die("Cannot read blob %s", sha1_to_hex(spec->sha1));
+		die("Cannot read blob %s", oid_to_hex(&spec->oid));
 
 	ALLOC_ARRAY(ends, size);
 	ends[cur++] = 0;
@@ -893,14 +893,14 @@ static void dump_diff_hacky_one(struct rev_info *rev, struct line_log_data *rang
 	if (!pair || !diff)
 		return;
 
-	if (pair->one->sha1_valid)
+	if (pair->one->oid_valid)
 		fill_line_ends(pair->one, &p_lines, &p_ends);
 	fill_line_ends(pair->two, &t_lines, &t_ends);
 
 	fprintf(opt->file, "%s%sdiff --git a/%s b/%s%s\n", prefix, c_meta, pair->one->path, pair->two->path, c_reset);
 	fprintf(opt->file, "%s%s--- %s%s%s\n", prefix, c_meta,
-	       pair->one->sha1_valid ? "a/" : "",
-	       pair->one->sha1_valid ? pair->one->path : "/dev/null",
+	       pair->one->oid_valid ? "a/" : "",
+	       pair->one->oid_valid ? pair->one->path : "/dev/null",
 	       c_reset);
 	fprintf(opt->file, "%s%s+++ b/%s%s\n", prefix, c_meta, pair->two->path, c_reset);
 	for (i = 0; i < range->ranges.nr; i++) {
@@ -1010,12 +1010,12 @@ static int process_diff_filepair(struct rev_info *rev,
 	if (rg->ranges.nr == 0)
 		return 0;
 
-	assert(pair->two->sha1_valid);
+	assert(pair->two->oid_valid);
 	diff_populate_filespec(pair->two, 0);
 	file_target.ptr = pair->two->data;
 	file_target.size = pair->two->size;
 
-	if (pair->one->sha1_valid) {
+	if (pair->one->oid_valid) {
 		diff_populate_filespec(pair->one, 0);
 		file_parent.ptr = pair->one->data;
 		file_parent.size = pair->one->size;
diff --git a/merge-recursive.c b/merge-recursive.c
index 65cb5d6c1f..48fe7e7386 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -56,11 +56,11 @@ static struct commit *make_virtual_commit(struct tree *tree, const char *comment
  * Since we use get_tree_entry(), which does not put the read object into
  * the object pool, we cannot rely on a == b.
  */
-static int sha_eq(const unsigned char *a, const unsigned char *b)
+static int oid_eq(const struct object_id *a, const struct object_id *b)
 {
 	if (!a && !b)
 		return 2;
-	return a && b && hashcmp(a, b) == 0;
+	return a && b && oidcmp(a, b) == 0;
 }
 
 enum rename_type {
@@ -90,7 +90,7 @@ struct rename_conflict_info {
 struct stage_data {
 	struct {
 		unsigned mode;
-		unsigned char sha[20];
+		struct object_id oid;
 	} stages[4];
 	struct rename_conflict_info *rename_conflict_info;
 	unsigned processed:1;
@@ -134,11 +134,11 @@ static inline void setup_rename_conflict_info(enum rename_type rename_type,
 		int ostage2 = ostage1 ^ 1;
 
 		ci->ren1_other.path = pair1->one->path;
-		hashcpy(ci->ren1_other.sha1, src_entry1->stages[ostage1].sha);
+		oidcpy(&ci->ren1_other.oid, &src_entry1->stages[ostage1].oid);
 		ci->ren1_other.mode = src_entry1->stages[ostage1].mode;
 
 		ci->ren2_other.path = pair2->one->path;
-		hashcpy(ci->ren2_other.sha1, src_entry2->stages[ostage2].sha);
+		oidcpy(&ci->ren2_other.oid, &src_entry2->stages[ostage2].oid);
 		ci->ren2_other.mode = src_entry2->stages[ostage2].mode;
 	}
 }
@@ -198,11 +198,11 @@ static void output_commit_title(struct merge_options *o, struct commit *commit)
 	}
 }
 
-static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
+static int add_cacheinfo(unsigned int mode, const struct object_id *oid,
 		const char *path, int stage, int refresh, int options)
 {
 	struct cache_entry *ce;
-	ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage,
+	ce = make_cache_entry(mode, oid ? oid->hash : null_sha1, path, stage,
 			      (refresh ? (CE_MATCH_REFRESH |
 					  CE_MATCH_IGNORE_MISSING) : 0 ));
 	if (!ce)
@@ -314,11 +314,11 @@ static struct stage_data *insert_stage_data(const char *path,
 	struct string_list_item *item;
 	struct stage_data *e = xcalloc(1, sizeof(struct stage_data));
 	get_tree_entry(o->object.oid.hash, path,
-			e->stages[1].sha, &e->stages[1].mode);
+			e->stages[1].oid.hash, &e->stages[1].mode);
 	get_tree_entry(a->object.oid.hash, path,
-			e->stages[2].sha, &e->stages[2].mode);
+			e->stages[2].oid.hash, &e->stages[2].mode);
 	get_tree_entry(b->object.oid.hash, path,
-			e->stages[3].sha, &e->stages[3].mode);
+			e->stages[3].oid.hash, &e->stages[3].mode);
 	item = string_list_insert(entries, path);
 	item->util = e;
 	return e;
@@ -349,7 +349,7 @@ static struct string_list *get_unmerged(void)
 		}
 		e = item->util;
 		e->stages[ce_stage(ce)].mode = ce->ce_mode;
-		hashcpy(e->stages[ce_stage(ce)].sha, ce->sha1);
+		hashcpy(e->stages[ce_stage(ce)].oid.hash, ce->sha1);
 	}
 
 	return unmerged;
@@ -552,13 +552,13 @@ static int update_stages(const char *path, const struct diff_filespec *o,
 		if (remove_file_from_cache(path))
 			return -1;
 	if (o)
-		if (add_cacheinfo(o->mode, o->sha1, path, 1, 0, options))
+		if (add_cacheinfo(o->mode, &o->oid, path, 1, 0, options))
 			return -1;
 	if (a)
-		if (add_cacheinfo(a->mode, a->sha1, path, 2, 0, options))
+		if (add_cacheinfo(a->mode, &a->oid, path, 2, 0, options))
 			return -1;
 	if (b)
-		if (add_cacheinfo(b->mode, b->sha1, path, 3, 0, options))
+		if (add_cacheinfo(b->mode, &b->oid, path, 3, 0, options))
 			return -1;
 	return 0;
 }
@@ -572,9 +572,9 @@ static void update_entry(struct stage_data *entry,
 	entry->stages[1].mode = o->mode;
 	entry->stages[2].mode = a->mode;
 	entry->stages[3].mode = b->mode;
-	hashcpy(entry->stages[1].sha, o->sha1);
-	hashcpy(entry->stages[2].sha, a->sha1);
-	hashcpy(entry->stages[3].sha, b->sha1);
+	oidcpy(&entry->stages[1].oid, &o->oid);
+	oidcpy(&entry->stages[2].oid, &a->oid);
+	oidcpy(&entry->stages[3].oid, &b->oid);
 }
 
 static int remove_file(struct merge_options *o, int clean,
@@ -736,7 +736,7 @@ static int make_room_for_path(struct merge_options *o, const char *path)
 }
 
 static void update_file_flags(struct merge_options *o,
-			      const unsigned char *sha,
+			      const struct object_id *oid,
 			      unsigned mode,
 			      const char *path,
 			      int update_cache,
@@ -760,11 +760,11 @@ static void update_file_flags(struct merge_options *o,
 			goto update_index;
 		}
 
-		buf = read_sha1_file(sha, &type, &size);
+		buf = read_sha1_file(oid->hash, &type, &size);
 		if (!buf)
-			die(_("cannot read object %s '%s'"), sha1_to_hex(sha), path);
+			die(_("cannot read object %s '%s'"), oid_to_hex(oid), path);
 		if (type != OBJ_BLOB)
-			die(_("blob expected for %s '%s'"), sha1_to_hex(sha), path);
+			die(_("blob expected for %s '%s'"), oid_to_hex(oid), path);
 		if (S_ISREG(mode)) {
 			struct strbuf strbuf = STRBUF_INIT;
 			if (convert_to_working_tree(path, buf, size, &strbuf)) {
@@ -799,27 +799,27 @@ static void update_file_flags(struct merge_options *o,
 			free(lnk);
 		} else
 			die(_("do not know what to do with %06o %s '%s'"),
-			    mode, sha1_to_hex(sha), path);
+			    mode, oid_to_hex(oid), path);
 		free(buf);
 	}
  update_index:
 	if (update_cache)
-		add_cacheinfo(mode, sha, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
+		add_cacheinfo(mode, oid, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
 }
 
 static void update_file(struct merge_options *o,
 			int clean,
-			const unsigned char *sha,
+			const struct object_id *oid,
 			unsigned mode,
 			const char *path)
 {
-	update_file_flags(o, sha, mode, path, o->call_depth || clean, !o->call_depth);
+	update_file_flags(o, oid, mode, path, o->call_depth || clean, !o->call_depth);
 }
 
 /* Low level file merging, update and removal */
 
 struct merge_file_info {
-	unsigned char sha[20];
+	struct object_id oid;
 	unsigned mode;
 	unsigned clean:1,
 		 merge:1;
@@ -871,9 +871,9 @@ static int merge_3way(struct merge_options *o,
 		name2 = mkpathdup("%s", branch2);
 	}
 
-	read_mmblob(&orig, one->sha1);
-	read_mmblob(&src1, a->sha1);
-	read_mmblob(&src2, b->sha1);
+	read_mmblob(&orig, one->oid.hash);
+	read_mmblob(&src1, a->oid.hash);
+	read_mmblob(&src2, b->oid.hash);
 
 	merge_status = ll_merge(result_buf, a->path, &orig, base_name,
 				&src1, name1, &src2, name2, &ll_opts);
@@ -902,13 +902,13 @@ static struct merge_file_info merge_file_1(struct merge_options *o,
 		result.clean = 0;
 		if (S_ISREG(a->mode)) {
 			result.mode = a->mode;
-			hashcpy(result.sha, a->sha1);
+			oidcpy(&result.oid, &a->oid);
 		} else {
 			result.mode = b->mode;
-			hashcpy(result.sha, b->sha1);
+			oidcpy(&result.oid, &b->oid);
 		}
 	} else {
-		if (!sha_eq(a->sha1, one->sha1) && !sha_eq(b->sha1, one->sha1))
+		if (!oid_eq(&a->oid, &one->oid) && !oid_eq(&b->oid, &one->oid))
 			result.merge = 1;
 
 		/*
@@ -924,10 +924,10 @@ static struct merge_file_info merge_file_1(struct merge_options *o,
 			}
 		}
 
-		if (sha_eq(a->sha1, b->sha1) || sha_eq(a->sha1, one->sha1))
-			hashcpy(result.sha, b->sha1);
-		else if (sha_eq(b->sha1, one->sha1))
-			hashcpy(result.sha, a->sha1);
+		if (oid_eq(&a->oid, &b->oid) || oid_eq(&a->oid, &one->oid))
+			oidcpy(&result.oid, &b->oid);
+		else if (oid_eq(&b->oid, &one->oid))
+			oidcpy(&result.oid, &a->oid);
 		else if (S_ISREG(a->mode)) {
 			mmbuffer_t result_buf;
 			int merge_status;
@@ -939,21 +939,23 @@ static struct merge_file_info merge_file_1(struct merge_options *o,
 				die(_("Failed to execute internal merge"));
 
 			if (write_sha1_file(result_buf.ptr, result_buf.size,
-					    blob_type, result.sha))
+					    blob_type, result.oid.hash))
 				die(_("Unable to add %s to database"),
 				    a->path);
 
 			free(result_buf.ptr);
 			result.clean = (merge_status == 0);
 		} else if (S_ISGITLINK(a->mode)) {
-			result.clean = merge_submodule(result.sha,
-						       one->path, one->sha1,
-						       a->sha1, b->sha1,
+			result.clean = merge_submodule(result.oid.hash,
+						       one->path,
+						       one->oid.hash,
+						       a->oid.hash,
+						       b->oid.hash,
 						       !o->call_depth);
 		} else if (S_ISLNK(a->mode)) {
-			hashcpy(result.sha, a->sha1);
+			oidcpy(&result.oid, &a->oid);
 
-			if (!sha_eq(a->sha1, b->sha1))
+			if (!oid_eq(&a->oid, &b->oid))
 				result.clean = 0;
 		} else {
 			die(_("unsupported object type in the tree"));
@@ -991,34 +993,34 @@ merge_file_special_markers(struct merge_options *o,
 
 static struct merge_file_info merge_file_one(struct merge_options *o,
 					 const char *path,
-					 const unsigned char *o_sha, int o_mode,
-					 const unsigned char *a_sha, int a_mode,
-					 const unsigned char *b_sha, int b_mode,
+					 const struct object_id *o_oid, int o_mode,
+					 const struct object_id *a_oid, int a_mode,
+					 const struct object_id *b_oid, int b_mode,
 					 const char *branch1,
 					 const char *branch2)
 {
 	struct diff_filespec one, a, b;
 
 	one.path = a.path = b.path = (char *)path;
-	hashcpy(one.sha1, o_sha);
+	oidcpy(&one.oid, o_oid);
 	one.mode = o_mode;
-	hashcpy(a.sha1, a_sha);
+	oidcpy(&a.oid, a_oid);
 	a.mode = a_mode;
-	hashcpy(b.sha1, b_sha);
+	oidcpy(&b.oid, b_oid);
 	b.mode = b_mode;
 	return merge_file_1(o, &one, &a, &b, branch1, branch2);
 }
 
 static void handle_change_delete(struct merge_options *o,
 				 const char *path,
-				 const unsigned char *o_sha, int o_mode,
-				 const unsigned char *a_sha, int a_mode,
-				 const unsigned char *b_sha, int b_mode,
+				 const struct object_id *o_oid, int o_mode,
+				 const struct object_id *a_oid, int a_mode,
+				 const struct object_id *b_oid, int b_mode,
 				 const char *change, const char *change_past)
 {
 	char *renamed = NULL;
 	if (dir_in_way(path, !o->call_depth)) {
-		renamed = unique_path(o, path, a_sha ? o->branch1 : o->branch2);
+		renamed = unique_path(o, path, a_oid ? o->branch1 : o->branch2);
 	}
 
 	if (o->call_depth) {
@@ -1028,20 +1030,20 @@ static void handle_change_delete(struct merge_options *o,
 		 * them, simply reuse the base version for virtual merge base.
 		 */
 		remove_file_from_cache(path);
-		update_file(o, 0, o_sha, o_mode, renamed ? renamed : path);
-	} else if (!a_sha) {
+		update_file(o, 0, o_oid, o_mode, renamed ? renamed : path);
+	} else if (!a_oid) {
 		if (!renamed) {
 			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
 			       "and %s in %s. Version %s of %s left in tree."),
 			       change, path, o->branch1, change_past,
 			       o->branch2, o->branch2, path);
-			update_file(o, 0, b_sha, b_mode, path);
+			update_file(o, 0, b_oid, b_mode, path);
 		} else {
 			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
 			       "and %s in %s. Version %s of %s left in tree at %s."),
 			       change, path, o->branch1, change_past,
 			       o->branch2, o->branch2, path, renamed);
-			update_file(o, 0, b_sha, b_mode, renamed);
+			update_file(o, 0, b_oid, b_mode, renamed);
 		}
 	} else {
 		if (!renamed) {
@@ -1054,7 +1056,7 @@ static void handle_change_delete(struct merge_options *o,
 			       "and %s in %s. Version %s of %s left in tree at %s."),
 			       change, path, o->branch2, change_past,
 			       o->branch1, o->branch1, path, renamed);
-			update_file(o, 0, a_sha, a_mode, renamed);
+			update_file(o, 0, a_oid, a_mode, renamed);
 		}
 		/*
 		 * No need to call update_file() on path when !renamed, since
@@ -1073,24 +1075,24 @@ static void conflict_rename_delete(struct merge_options *o,
 {
 	const struct diff_filespec *orig = pair->one;
 	const struct diff_filespec *dest = pair->two;
-	const unsigned char *a_sha = NULL;
-	const unsigned char *b_sha = NULL;
+	const struct object_id *a_oid = NULL;
+	const struct object_id *b_oid = NULL;
 	int a_mode = 0;
 	int b_mode = 0;
 
 	if (rename_branch == o->branch1) {
-		a_sha = dest->sha1;
+		a_oid = &dest->oid;
 		a_mode = dest->mode;
 	} else {
-		b_sha = dest->sha1;
+		b_oid = &dest->oid;
 		b_mode = dest->mode;
 	}
 
 	handle_change_delete(o,
 			     o->call_depth ? orig->path : dest->path,
-			     orig->sha1, orig->mode,
-			     a_sha, a_mode,
-			     b_sha, b_mode,
+			     &orig->oid, orig->mode,
+			     a_oid, a_mode,
+			     b_oid, b_mode,
 			     _("rename"), _("renamed"));
 
 	if (o->call_depth) {
@@ -1107,11 +1109,11 @@ static struct diff_filespec *filespec_from_entry(struct diff_filespec *target,
 						 struct stage_data *entry,
 						 int stage)
 {
-	unsigned char *sha = entry->stages[stage].sha;
+	struct object_id *oid = &entry->stages[stage].oid;
 	unsigned mode = entry->stages[stage].mode;
-	if (mode == 0 || is_null_sha1(sha))
+	if (mode == 0 || is_null_oid(oid))
 		return NULL;
-	hashcpy(target->sha1, sha);
+	oidcpy(&target->oid, oid);
 	target->mode = mode;
 	return target;
 }
@@ -1140,7 +1142,7 @@ static void handle_file(struct merge_options *o,
 	add = filespec_from_entry(&other, dst_entry, stage ^ 1);
 	if (add) {
 		char *add_name = unique_path(o, rename->path, other_branch);
-		update_file(o, 0, add->sha1, add->mode, add_name);
+		update_file(o, 0, &add->oid, add->mode, add_name);
 
 		remove_file(o, 0, rename->path, 0);
 		dst_name = unique_path(o, rename->path, cur_branch);
@@ -1151,7 +1153,7 @@ static void handle_file(struct merge_options *o,
 			       rename->path, other_branch, dst_name);
 		}
 	}
-	update_file(o, 0, rename->sha1, rename->mode, dst_name);
+	update_file(o, 0, &rename->oid, rename->mode, dst_name);
 	if (stage == 2)
 		update_stages(rename->path, NULL, rename, add);
 	else
@@ -1180,9 +1182,9 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		struct diff_filespec other;
 		struct diff_filespec *add;
 		mfi = merge_file_one(o, one->path,
-				 one->sha1, one->mode,
-				 a->sha1, a->mode,
-				 b->sha1, b->mode,
+				 &one->oid, one->mode,
+				 &a->oid, a->mode,
+				 &b->oid, b->mode,
 				 ci->branch1, ci->branch2);
 		/*
 		 * FIXME: For rename/add-source conflicts (if we could detect
@@ -1190,7 +1192,7 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		 * pathname and then either rename the add-source file to that
 		 * unique path, or use that unique path instead of src here.
 		 */
-		update_file(o, 0, mfi.sha, mfi.mode, one->path);
+		update_file(o, 0, &mfi.oid, mfi.mode, one->path);
 
 		/*
 		 * Above, we put the merged content at the merge-base's
@@ -1202,12 +1204,12 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		 */
 		add = filespec_from_entry(&other, ci->dst_entry1, 2 ^ 1);
 		if (add)
-			update_file(o, 0, add->sha1, add->mode, a->path);
+			update_file(o, 0, &add->oid, add->mode, a->path);
 		else
 			remove_file_from_cache(a->path);
 		add = filespec_from_entry(&other, ci->dst_entry2, 3 ^ 1);
 		if (add)
-			update_file(o, 0, add->sha1, add->mode, b->path);
+			update_file(o, 0, &add->oid, add->mode, b->path);
 		else
 			remove_file_from_cache(b->path);
 	} else {
@@ -1253,16 +1255,16 @@ static void conflict_rename_rename_2to1(struct merge_options *o,
 		 * again later for the non-recursive merge.
 		 */
 		remove_file(o, 0, path, 0);
-		update_file(o, 0, mfi_c1.sha, mfi_c1.mode, a->path);
-		update_file(o, 0, mfi_c2.sha, mfi_c2.mode, b->path);
+		update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, a->path);
+		update_file(o, 0, &mfi_c2.oid, mfi_c2.mode, b->path);
 	} else {
 		char *new_path1 = unique_path(o, path, ci->branch1);
 		char *new_path2 = unique_path(o, path, ci->branch2);
 		output(o, 1, _("Renaming %s to %s and %s to %s instead"),
 		       a->path, new_path1, b->path, new_path2);
 		remove_file(o, 0, path, 0);
-		update_file(o, 0, mfi_c1.sha, mfi_c1.mode, new_path1);
-		update_file(o, 0, mfi_c2.sha, mfi_c2.mode, new_path2);
+		update_file(o, 0, &mfi_c1.oid, mfi_c1.mode, new_path1);
+		update_file(o, 0, &mfi_c2.oid, mfi_c2.mode, new_path2);
 		free(new_path2);
 		free(new_path1);
 	}
@@ -1421,13 +1423,15 @@ static int process_renames(struct merge_options *o,
 			remove_file(o, 1, ren1_src,
 				    renamed_stage == 2 || !was_tracked(ren1_src));
 
-			hashcpy(src_other.sha1, ren1->src_entry->stages[other_stage].sha);
+			oidcpy(&src_other.oid,
+			       &ren1->src_entry->stages[other_stage].oid);
 			src_other.mode = ren1->src_entry->stages[other_stage].mode;
-			hashcpy(dst_other.sha1, ren1->dst_entry->stages[other_stage].sha);
+			oidcpy(&dst_other.oid,
+			       &ren1->dst_entry->stages[other_stage].oid);
 			dst_other.mode = ren1->dst_entry->stages[other_stage].mode;
 			try_merge = 0;
 
-			if (sha_eq(src_other.sha1, null_sha1)) {
+			if (oid_eq(&src_other.oid, &null_oid)) {
 				setup_rename_conflict_info(RENAME_DELETE,
 							   ren1->pair,
 							   NULL,
@@ -1439,7 +1443,7 @@ static int process_renames(struct merge_options *o,
 							   NULL,
 							   NULL);
 			} else if ((dst_other.mode == ren1->pair->two->mode) &&
-				   sha_eq(dst_other.sha1, ren1->pair->two->sha1)) {
+				   oid_eq(&dst_other.oid, &ren1->pair->two->oid)) {
 				/*
 				 * Added file on the other side identical to
 				 * the file being renamed: clean merge.
@@ -1449,12 +1453,12 @@ static int process_renames(struct merge_options *o,
 				 * update_file().
 				 */
 				update_file_flags(o,
-						  ren1->pair->two->sha1,
+						  &ren1->pair->two->oid,
 						  ren1->pair->two->mode,
 						  ren1_dst,
 						  1, /* update_cache */
 						  0  /* update_wd    */);
-			} else if (!sha_eq(dst_other.sha1, null_sha1)) {
+			} else if (!oid_eq(&dst_other.oid, &null_oid)) {
 				clean_merge = 0;
 				try_merge = 1;
 				output(o, 1, _("CONFLICT (rename/add): Rename %s->%s in %s. "
@@ -1463,17 +1467,21 @@ static int process_renames(struct merge_options *o,
 				       ren1_dst, branch2);
 				if (o->call_depth) {
 					struct merge_file_info mfi;
-					mfi = merge_file_one(o, ren1_dst, null_sha1, 0,
-							 ren1->pair->two->sha1, ren1->pair->two->mode,
-							 dst_other.sha1, dst_other.mode,
+					mfi = merge_file_one(o, ren1_dst, &null_oid, 0,
+							 &ren1->pair->two->oid,
+							 ren1->pair->two->mode,
+							 &dst_other.oid,
+							 dst_other.mode,
 							 branch1, branch2);
 					output(o, 1, _("Adding merged %s"), ren1_dst);
-					update_file(o, 0, mfi.sha, mfi.mode, ren1_dst);
+					update_file(o, 0, &mfi.oid,
+						    mfi.mode, ren1_dst);
 					try_merge = 0;
 				} else {
 					char *new_path = unique_path(o, ren1_dst, branch2);
 					output(o, 1, _("Adding as %s instead"), new_path);
-					update_file(o, 0, dst_other.sha1, dst_other.mode, new_path);
+					update_file(o, 0, &dst_other.oid,
+						    dst_other.mode, new_path);
 					free(new_path);
 				}
 			} else
@@ -1511,30 +1519,30 @@ static int process_renames(struct merge_options *o,
 	return clean_merge;
 }
 
-static unsigned char *stage_sha(const unsigned char *sha, unsigned mode)
+static struct object_id *stage_oid(const struct object_id *oid, unsigned mode)
 {
-	return (is_null_sha1(sha) || mode == 0) ? NULL: (unsigned char *)sha;
+	return (is_null_oid(oid) || mode == 0) ? NULL: (struct object_id *)oid;
 }
 
-static int read_sha1_strbuf(const unsigned char *sha1, struct strbuf *dst)
+static int read_oid_strbuf(const struct object_id *oid, struct strbuf *dst)
 {
 	void *buf;
 	enum object_type type;
 	unsigned long size;
-	buf = read_sha1_file(sha1, &type, &size);
+	buf = read_sha1_file(oid->hash, &type, &size);
 	if (!buf)
-		return error(_("cannot read object %s"), sha1_to_hex(sha1));
+		return error(_("cannot read object %s"), oid_to_hex(oid));
 	if (type != OBJ_BLOB) {
 		free(buf);
-		return error(_("object %s is not a blob"), sha1_to_hex(sha1));
+		return error(_("object %s is not a blob"), oid_to_hex(oid));
 	}
 	strbuf_attach(dst, buf, size, size + 1);
 	return 0;
 }
 
-static int blob_unchanged(const unsigned char *o_sha,
+static int blob_unchanged(const struct object_id *o_oid,
 			  unsigned o_mode,
-			  const unsigned char *a_sha,
+			  const struct object_id *a_oid,
 			  unsigned a_mode,
 			  int renormalize, const char *path)
 {
@@ -1544,13 +1552,13 @@ static int blob_unchanged(const unsigned char *o_sha,
 
 	if (a_mode != o_mode)
 		return 0;
-	if (sha_eq(o_sha, a_sha))
+	if (oid_eq(o_oid, a_oid))
 		return 1;
 	if (!renormalize)
 		return 0;
 
-	assert(o_sha && a_sha);
-	if (read_sha1_strbuf(o_sha, &o) || read_sha1_strbuf(a_sha, &a))
+	assert(o_oid && a_oid);
+	if (read_oid_strbuf(o_oid, &o) || read_oid_strbuf(a_oid, &a))
 		goto error_return;
 	/*
 	 * Note: binary | is used so that both renormalizations are
@@ -1569,23 +1577,23 @@ error_return:
 
 static void handle_modify_delete(struct merge_options *o,
 				 const char *path,
-				 unsigned char *o_sha, int o_mode,
-				 unsigned char *a_sha, int a_mode,
-				 unsigned char *b_sha, int b_mode)
+				 struct object_id *o_oid, int o_mode,
+				 struct object_id *a_oid, int a_mode,
+				 struct object_id *b_oid, int b_mode)
 {
 	handle_change_delete(o,
 			     path,
-			     o_sha, o_mode,
-			     a_sha, a_mode,
-			     b_sha, b_mode,
+			     o_oid, o_mode,
+			     a_oid, a_mode,
+			     b_oid, b_mode,
 			     _("modify"), _("modified"));
 }
 
 static int merge_content(struct merge_options *o,
 			 const char *path,
-			 unsigned char *o_sha, int o_mode,
-			 unsigned char *a_sha, int a_mode,
-			 unsigned char *b_sha, int b_mode,
+			 struct object_id *o_oid, int o_mode,
+			 struct object_id *a_oid, int a_mode,
+			 struct object_id *b_oid, int b_mode,
 			 struct rename_conflict_info *rename_conflict_info)
 {
 	const char *reason = _("content");
@@ -1594,16 +1602,16 @@ static int merge_content(struct merge_options *o,
 	struct diff_filespec one, a, b;
 	unsigned df_conflict_remains = 0;
 
-	if (!o_sha) {
+	if (!o_oid) {
 		reason = _("add/add");
-		o_sha = (unsigned char *)null_sha1;
+		o_oid = (struct object_id *)&null_oid;
 	}
 	one.path = a.path = b.path = (char *)path;
-	hashcpy(one.sha1, o_sha);
+	oidcpy(&one.oid, o_oid);
 	one.mode = o_mode;
-	hashcpy(a.sha1, a_sha);
+	oidcpy(&a.oid, a_oid);
 	a.mode = a_mode;
-	hashcpy(b.sha1, b_sha);
+	oidcpy(&b.oid, b_oid);
 	b.mode = b_mode;
 
 	if (rename_conflict_info) {
@@ -1627,7 +1635,7 @@ static int merge_content(struct merge_options *o,
 					 o->branch2, path2);
 
 	if (mfi.clean && !df_conflict_remains &&
-	    sha_eq(mfi.sha, a_sha) && mfi.mode == a_mode) {
+	    oid_eq(&mfi.oid, a_oid) && mfi.mode == a_mode) {
 		int path_renamed_outside_HEAD;
 		output(o, 3, _("Skipped %s (merged same as existing)"), path);
 		/*
@@ -1638,7 +1646,7 @@ static int merge_content(struct merge_options *o,
 		 */
 		path_renamed_outside_HEAD = !path2 || !strcmp(path, path2);
 		if (!path_renamed_outside_HEAD) {
-			add_cacheinfo(mfi.mode, mfi.sha, path,
+			add_cacheinfo(mfi.mode, &mfi.oid, path,
 				      0, (!o->call_depth), 0);
 			return mfi.clean;
 		}
@@ -1664,7 +1672,7 @@ static int merge_content(struct merge_options *o,
 			else {
 				int file_from_stage2 = was_tracked(path);
 				struct diff_filespec merged;
-				hashcpy(merged.sha1, mfi.sha);
+				oidcpy(&merged.oid, &mfi.oid);
 				merged.mode = mfi.mode;
 
 				update_stages(path, NULL,
@@ -1675,11 +1683,11 @@ static int merge_content(struct merge_options *o,
 		}
 		new_path = unique_path(o, path, rename_conflict_info->branch1);
 		output(o, 1, _("Adding as %s instead"), new_path);
-		update_file(o, 0, mfi.sha, mfi.mode, new_path);
+		update_file(o, 0, &mfi.oid, mfi.mode, new_path);
 		free(new_path);
 		mfi.clean = 0;
 	} else {
-		update_file(o, mfi.clean, mfi.sha, mfi.mode, path);
+		update_file(o, mfi.clean, &mfi.oid, mfi.mode, path);
 	}
 	return mfi.clean;
 
@@ -1694,9 +1702,9 @@ static int process_entry(struct merge_options *o,
 	unsigned o_mode = entry->stages[1].mode;
 	unsigned a_mode = entry->stages[2].mode;
 	unsigned b_mode = entry->stages[3].mode;
-	unsigned char *o_sha = stage_sha(entry->stages[1].sha, o_mode);
-	unsigned char *a_sha = stage_sha(entry->stages[2].sha, a_mode);
-	unsigned char *b_sha = stage_sha(entry->stages[3].sha, b_mode);
+	struct object_id *o_oid = stage_oid(&entry->stages[1].oid, o_mode);
+	struct object_id *a_oid = stage_oid(&entry->stages[2].oid, a_mode);
+	struct object_id *b_oid = stage_oid(&entry->stages[3].oid, b_mode);
 
 	entry->processed = 1;
 	if (entry->rename_conflict_info) {
@@ -1705,7 +1713,7 @@ static int process_entry(struct merge_options *o,
 		case RENAME_NORMAL:
 		case RENAME_ONE_FILE_TO_ONE:
 			clean_merge = merge_content(o, path,
-						    o_sha, o_mode, a_sha, a_mode, b_sha, b_mode,
+						    o_oid, o_mode, a_oid, a_mode, b_oid, b_mode,
 						    conflict_info);
 			break;
 		case RENAME_DELETE:
@@ -1726,45 +1734,45 @@ static int process_entry(struct merge_options *o,
 			entry->processed = 0;
 			break;
 		}
-	} else if (o_sha && (!a_sha || !b_sha)) {
+	} else if (o_oid && (!a_oid || !b_oid)) {
 		/* Case A: Deleted in one */
-		if ((!a_sha && !b_sha) ||
-		    (!b_sha && blob_unchanged(o_sha, o_mode, a_sha, a_mode, normalize, path)) ||
-		    (!a_sha && blob_unchanged(o_sha, o_mode, b_sha, b_mode, normalize, path))) {
+		if ((!a_oid && !b_oid) ||
+		    (!b_oid && blob_unchanged(o_oid, o_mode, a_oid, a_mode, normalize, path)) ||
+		    (!a_oid && blob_unchanged(o_oid, o_mode, b_oid, b_mode, normalize, path))) {
 			/* Deleted in both or deleted in one and
 			 * unchanged in the other */
-			if (a_sha)
+			if (a_oid)
 				output(o, 2, _("Removing %s"), path);
 			/* do not touch working file if it did not exist */
-			remove_file(o, 1, path, !a_sha);
+			remove_file(o, 1, path, !a_oid);
 		} else {
 			/* Modify/delete; deleted side may have put a directory in the way */
 			clean_merge = 0;
-			handle_modify_delete(o, path, o_sha, o_mode,
-					     a_sha, a_mode, b_sha, b_mode);
+			handle_modify_delete(o, path, o_oid, o_mode,
+					     a_oid, a_mode, b_oid, b_mode);
 		}
-	} else if ((!o_sha && a_sha && !b_sha) ||
-		   (!o_sha && !a_sha && b_sha)) {
+	} else if ((!o_oid && a_oid && !b_oid) ||
+		   (!o_oid && !a_oid && b_oid)) {
 		/* Case B: Added in one. */
 		/* [nothing|directory] -> ([nothing|directory], file) */
 
 		const char *add_branch;
 		const char *other_branch;
 		unsigned mode;
-		const unsigned char *sha;
+		const struct object_id *oid;
 		const char *conf;
 
-		if (a_sha) {
+		if (a_oid) {
 			add_branch = o->branch1;
 			other_branch = o->branch2;
 			mode = a_mode;
-			sha = a_sha;
+			oid = a_oid;
 			conf = _("file/directory");
 		} else {
 			add_branch = o->branch2;
 			other_branch = o->branch1;
 			mode = b_mode;
-			sha = b_sha;
+			oid = b_oid;
 			conf = _("directory/file");
 		}
 		if (dir_in_way(path, !o->call_depth)) {
@@ -1773,22 +1781,22 @@ static int process_entry(struct merge_options *o,
 			output(o, 1, _("CONFLICT (%s): There is a directory with name %s in %s. "
 			       "Adding %s as %s"),
 			       conf, path, other_branch, path, new_path);
-			update_file(o, 0, sha, mode, new_path);
+			update_file(o, 0, oid, mode, new_path);
 			if (o->call_depth)
 				remove_file_from_cache(path);
 			free(new_path);
 		} else {
 			output(o, 2, _("Adding %s"), path);
 			/* do not overwrite file if already present */
-			update_file_flags(o, sha, mode, path, 1, !a_sha);
+			update_file_flags(o, oid, mode, path, 1, !a_oid);
 		}
-	} else if (a_sha && b_sha) {
+	} else if (a_oid && b_oid) {
 		/* Case C: Added in both (check for same permissions) and */
 		/* case D: Modified in both, but differently. */
 		clean_merge = merge_content(o, path,
-					    o_sha, o_mode, a_sha, a_mode, b_sha, b_mode,
+					    o_oid, o_mode, a_oid, a_mode, b_oid, b_mode,
 					    NULL);
-	} else if (!o_sha && !a_sha && !b_sha) {
+	} else if (!o_oid && !a_oid && !b_oid) {
 		/*
 		 * this entry was deleted altogether. a_mode == 0 means
 		 * we had that path and want to actively remove it.
@@ -1813,7 +1821,7 @@ int merge_trees(struct merge_options *o,
 		common = shift_tree_object(head, common, o->subtree_shift);
 	}
 
-	if (sha_eq(common->object.oid.hash, merge->object.oid.hash)) {
+	if (oid_eq(&common->object.oid, &merge->object.oid)) {
 		output(o, 0, _("Already up-to-date!"));
 		*result = head;
 		return 1;
@@ -1974,11 +1982,11 @@ int merge_recursive(struct merge_options *o,
 	return clean;
 }
 
-static struct commit *get_ref(const unsigned char *sha1, const char *name)
+static struct commit *get_ref(const struct object_id *oid, const char *name)
 {
 	struct object *object;
 
-	object = deref_tag(parse_object(sha1), name, strlen(name));
+	object = deref_tag(parse_object(oid->hash), name, strlen(name));
 	if (!object)
 		return NULL;
 	if (object->type == OBJ_TREE)
@@ -1991,10 +1999,10 @@ static struct commit *get_ref(const unsigned char *sha1, const char *name)
 }
 
 int merge_recursive_generic(struct merge_options *o,
-			    const unsigned char *head,
-			    const unsigned char *merge,
+			    const struct object_id *head,
+			    const struct object_id *merge,
 			    int num_base_list,
-			    const unsigned char **base_list,
+			    const struct object_id **base_list,
 			    struct commit **result)
 {
 	int clean;
@@ -2007,9 +2015,9 @@ int merge_recursive_generic(struct merge_options *o,
 		int i;
 		for (i = 0; i < num_base_list; ++i) {
 			struct commit *base;
-			if (!(base = get_ref(base_list[i], sha1_to_hex(base_list[i]))))
+			if (!(base = get_ref(base_list[i], oid_to_hex(base_list[i]))))
 				return error(_("Could not parse object '%s'"),
-					sha1_to_hex(base_list[i]));
+					oid_to_hex(base_list[i]));
 			commit_list_insert(base, &ca);
 		}
 	}
diff --git a/merge-recursive.h b/merge-recursive.h
index 52f0201f68..d415724aea 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -49,10 +49,10 @@ int merge_trees(struct merge_options *o,
  * virtual commits and call merge_recursive() proper.
  */
 int merge_recursive_generic(struct merge_options *o,
-			    const unsigned char *head,
-			    const unsigned char *merge,
+			    const struct object_id *head,
+			    const struct object_id *merge,
 			    int num_ca,
-			    const unsigned char **ca,
+			    const struct object_id **ca,
 			    struct commit **result);
 
 void init_merge_options(struct merge_options *o);
diff --git a/notes-merge.c b/notes-merge.c
index b7814c9b64..1b58a14ebc 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -41,14 +41,14 @@ static int verify_notes_filepair(struct diff_filepair *p, unsigned char *sha1)
 	switch (p->status) {
 	case DIFF_STATUS_MODIFIED:
 		assert(p->one->mode == p->two->mode);
-		assert(!is_null_sha1(p->one->sha1));
-		assert(!is_null_sha1(p->two->sha1));
+		assert(!is_null_oid(&p->one->oid));
+		assert(!is_null_oid(&p->two->oid));
 		break;
 	case DIFF_STATUS_ADDED:
-		assert(is_null_sha1(p->one->sha1));
+		assert(is_null_oid(&p->one->oid));
 		break;
 	case DIFF_STATUS_DELETED:
-		assert(is_null_sha1(p->two->sha1));
+		assert(is_null_oid(&p->two->oid));
 		break;
 	default:
 		return -1;
@@ -142,27 +142,27 @@ static struct notes_merge_pair *diff_tree_remote(struct notes_merge_options *o,
 		if (verify_notes_filepair(p, obj)) {
 			trace_printf("\t\tCannot merge entry '%s' (%c): "
 			       "%.7s -> %.7s. Skipping!\n", p->one->path,
-			       p->status, sha1_to_hex(p->one->sha1),
-			       sha1_to_hex(p->two->sha1));
+			       p->status, oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
 			continue;
 		}
 		mp = find_notes_merge_pair_pos(changes, len, obj, 1, &occupied);
 		if (occupied) {
 			/* We've found an addition/deletion pair */
 			assert(!hashcmp(mp->obj, obj));
-			if (is_null_sha1(p->one->sha1)) { /* addition */
+			if (is_null_oid(&p->one->oid)) { /* addition */
 				assert(is_null_sha1(mp->remote));
-				hashcpy(mp->remote, p->two->sha1);
-			} else if (is_null_sha1(p->two->sha1)) { /* deletion */
+				hashcpy(mp->remote, p->two->oid.hash);
+			} else if (is_null_oid(&p->two->oid)) { /* deletion */
 				assert(is_null_sha1(mp->base));
-				hashcpy(mp->base, p->one->sha1);
+				hashcpy(mp->base, p->one->oid.hash);
 			} else
 				assert(!"Invalid existing change recorded");
 		} else {
 			hashcpy(mp->obj, obj);
-			hashcpy(mp->base, p->one->sha1);
+			hashcpy(mp->base, p->one->oid.hash);
 			hashcpy(mp->local, uninitialized);
-			hashcpy(mp->remote, p->two->sha1);
+			hashcpy(mp->remote, p->two->oid.hash);
 			len++;
 		}
 		trace_printf("\t\tStored remote change for %s: %.7s -> %.7s\n",
@@ -203,21 +203,21 @@ static void diff_tree_local(struct notes_merge_options *o,
 		if (verify_notes_filepair(p, obj)) {
 			trace_printf("\t\tCannot merge entry '%s' (%c): "
 			       "%.7s -> %.7s. Skipping!\n", p->one->path,
-			       p->status, sha1_to_hex(p->one->sha1),
-			       sha1_to_hex(p->two->sha1));
+			       p->status, oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
 			continue;
 		}
 		mp = find_notes_merge_pair_pos(changes, len, obj, 0, &match);
 		if (!match) {
 			trace_printf("\t\tIgnoring local-only change for %s: "
 			       "%.7s -> %.7s\n", sha1_to_hex(obj),
-			       sha1_to_hex(p->one->sha1),
-			       sha1_to_hex(p->two->sha1));
+			       oid_to_hex(&p->one->oid),
+			       oid_to_hex(&p->two->oid));
 			continue;
 		}
 
 		assert(!hashcmp(mp->obj, obj));
-		if (is_null_sha1(p->two->sha1)) { /* deletion */
+		if (is_null_oid(&p->two->oid)) { /* deletion */
 			/*
 			 * Either this is a true deletion (1), or it is part
 			 * of an A/D pair (2), or D/A pair (3):
@@ -229,7 +229,7 @@ static void diff_tree_local(struct notes_merge_options *o,
 			 */
 			if (!hashcmp(mp->local, uninitialized))
 				hashclr(mp->local);
-		} else if (is_null_sha1(p->one->sha1)) { /* addition */
+		} else if (is_null_oid(&p->one->oid)) { /* addition */
 			/*
 			 * Either this is a true addition (1), or it is part
 			 * of an A/D pair (2), or D/A pair (3):
@@ -240,16 +240,16 @@ static void diff_tree_local(struct notes_merge_options *o,
 			 */
 			assert(is_null_sha1(mp->local) ||
 			       !hashcmp(mp->local, uninitialized));
-			hashcpy(mp->local, p->two->sha1);
+			hashcpy(mp->local, p->two->oid.hash);
 		} else { /* modification */
 			/*
 			 * This is a true modification. p->one->sha1 shall
 			 * match mp->base, and mp->local shall be uninitialized.
 			 * Set mp->local to p->two->sha1.
 			 */
-			assert(!hashcmp(p->one->sha1, mp->base));
+			assert(!hashcmp(p->one->oid.hash, mp->base));
 			assert(!hashcmp(mp->local, uninitialized));
-			hashcpy(mp->local, p->two->sha1);
+			hashcpy(mp->local, p->two->oid.hash);
 		}
 		trace_printf("\t\tStored local change for %s: %.7s -> %.7s\n",
 		       sha1_to_hex(mp->obj), sha1_to_hex(mp->base),
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 1f38076411..dac3a22297 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1725,14 +1725,14 @@ static int verify_lock(struct ref_lock *lock,
 			errno = save_errno;
 			return -1;
 		} else {
-			hashclr(lock->old_oid.hash);
+			oidclr(&lock->old_oid);
 			return 0;
 		}
 	}
 	if (old_sha1 && hashcmp(lock->old_oid.hash, old_sha1)) {
 		strbuf_addf(err, "ref %s is at %s but expected %s",
 			    lock->ref_name,
-			    sha1_to_hex(lock->old_oid.hash),
+			    oid_to_hex(&lock->old_oid),
 			    sha1_to_hex(old_sha1));
 		errno = EBUSY;
 		return -1;
diff --git a/submodule-config.c b/submodule-config.c
index db1847ff68..077db4054f 100644
--- a/submodule-config.c
+++ b/submodule-config.c
@@ -377,7 +377,7 @@ static int gitmodule_sha1_from_commit(const unsigned char *commit_sha1,
 	int ret = 0;
 
 	if (is_null_sha1(commit_sha1)) {
-		hashcpy(gitmodules_sha1, null_sha1);
+		hashclr(gitmodules_sha1);
 		return 1;
 	}
 
diff --git a/submodule.c b/submodule.c
index abc2ac2a10..1b5cdfb7e7 100644
--- a/submodule.c
+++ b/submodule.c
@@ -445,7 +445,7 @@ static void collect_submodules_from_diff(struct diff_queue_struct *q,
 		struct diff_filepair *p = q->queue[i];
 		if (!S_ISGITLINK(p->two->mode))
 			continue;
-		if (submodule_needs_pushing(p->two->path, p->two->sha1))
+		if (submodule_needs_pushing(p->two->path, p->two->oid.hash))
 			string_list_insert(needs_pushing, p->two->path);
 	}
 }
@@ -577,7 +577,7 @@ static void submodule_collect_changed_cb(struct diff_queue_struct *q,
 			 * being moved around. */
 			struct string_list_item *path;
 			path = unsorted_string_list_lookup(&changed_submodule_paths, p->two->path);
-			if (!path && !is_submodule_commit_present(p->two->path, p->two->sha1))
+			if (!path && !is_submodule_commit_present(p->two->path, p->two->oid.hash))
 				string_list_append(&changed_submodule_paths, xstrdup(p->two->path));
 		} else {
 			/* Submodule is new or was moved here */
diff --git a/t/helper/test-submodule-config.c b/t/helper/test-submodule-config.c
index dab8c27768..7922ffba1d 100644
--- a/t/helper/test-submodule-config.c
+++ b/t/helper/test-submodule-config.c
@@ -49,7 +49,7 @@ int main(int argc, char **argv)
 		path_or_name = arg[1];
 
 		if (commit[0] == '\0')
-			hashcpy(commit_sha1, null_sha1);
+			hashclr(commit_sha1);
 		else if (get_sha1(commit, commit_sha1) < 0)
 			die_usage(argc, argv, "Commit not found.");
 
diff --git a/wt-status.c b/wt-status.c
index c19b52ce87..de62ab2149 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -432,7 +432,8 @@ static void wt_status_collect_changed_cb(struct diff_queue_struct *q,
 			d->worktree_status = p->status;
 		d->dirty_submodule = p->two->dirty_submodule;
 		if (S_ISGITLINK(p->two->mode))
-			d->new_submodule_commits = !!hashcmp(p->one->sha1, p->two->sha1);
+			d->new_submodule_commits = !!oidcmp(&p->one->oid,
+							    &p->two->oid);
 	}
 }