sha1_file: convert read_sha1_file to struct object_id

Convert read_sha1_file to take a pointer to struct object_id and rename
it read_object_file.  Do the same for read_sha1_file_extended.

Convert one use in grep.c to use the new function without any other code
change, since the pointer being passed is a void pointer that is already
initialized with a pointer to struct object_id.  Update the declaration
and definitions of the modified functions, and apply the following
semantic patch to convert the remaining callers:

@@
expression E1, E2, E3;
@@
- read_sha1_file(E1.hash, E2, E3)
+ read_object_file(&E1, E2, E3)

@@
expression E1, E2, E3;
@@
- read_sha1_file(E1->hash, E2, E3)
+ read_object_file(E1, E2, E3)

@@
expression E1, E2, E3, E4;
@@
- read_sha1_file_extended(E1.hash, E2, E3, E4)
+ read_object_file_extended(&E1, E2, E3, E4)

@@
expression E1, E2, E3, E4;
@@
- read_sha1_file_extended(E1->hash, E2, E3, E4)
+ read_object_file_extended(E1, E2, E3, E4)

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/tag.c b/builtin/tag.c
index 11a9883..86450ba 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -168,7 +168,7 @@ static void write_tag_body(int fd, const struct object_id *oid)
 	enum object_type type;
 	char *buf, *sp;
 
-	buf = read_sha1_file(oid->hash, &type, &size);
+	buf = read_object_file(oid, &type, &size);
 	if (!buf)
 		return;
 	/* skip header */
@@ -304,7 +304,7 @@ static void create_reflog_msg(const struct object_id *oid, struct strbuf *sb)
 		strbuf_addstr(sb, "object of unknown type");
 		break;
 	case OBJ_COMMIT:
-		if ((buf = read_sha1_file(oid->hash, &type, &size)) != NULL) {
+		if ((buf = read_object_file(oid, &type, &size)) != NULL) {
 			subject_len = find_commit_subject(buf, &subject_start);
 			strbuf_insert(sb, sb->len, subject_start, subject_len);
 		} else {