convert object type handling from a string to a number

We currently have two parallel notation for dealing with object types
in the code: a string and a numerical value.  One of them is obviously
redundent, and the most used one requires more stack space and a bunch
of strcmp() all over the place.

This is an initial step for the removal of the version using a char array
found in object reading code paths.  The patch is unfortunately large but
there is no sane way to split it in smaller parts without breaking the
system.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/convert-objects.c b/convert-objects.c
index a630132..b5f41ae 100644
--- a/convert-objects.c
+++ b/convert-objects.c
@@ -284,27 +284,27 @@
 static struct entry * convert_entry(unsigned char *sha1)
 {
 	struct entry *entry = lookup_entry(sha1);
-	char type[20];
+	enum object_type type;
 	void *buffer, *data;
 	unsigned long size;
 
 	if (entry->converted)
 		return entry;
-	data = read_sha1_file(sha1, type, &size);
+	data = read_sha1_file(sha1, &type, &size);
 	if (!data)
 		die("unable to read object %s", sha1_to_hex(sha1));
 
 	buffer = xmalloc(size);
 	memcpy(buffer, data, size);
 
-	if (!strcmp(type, blob_type)) {
+	if (type == OBJ_BLOB) {
 		write_sha1_file(buffer, size, blob_type, entry->new_sha1);
-	} else if (!strcmp(type, tree_type))
+	} else if (type == OBJ_TREE)
 		convert_tree(buffer, size, entry->new_sha1);
-	else if (!strcmp(type, commit_type))
+	else if (type == OBJ_COMMIT)
 		convert_commit(buffer, size, entry->new_sha1);
 	else
-		die("unknown object type '%s' in %s", type, sha1_to_hex(sha1));
+		die("unknown object type %d in %s", type, sha1_to_hex(sha1));
 	entry->converted = 1;
 	free(buffer);
 	free(data);