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/builtin-reflog.c b/builtin-reflog.c
index cefb40d..186aabc 100644
--- a/builtin-reflog.c
+++ b/builtin-reflog.c
@@ -55,8 +55,8 @@
 	desc.buf = tree->buffer;
 	desc.size = tree->size;
 	if (!desc.buf) {
-		char type[20];
-		void *data = read_sha1_file(sha1, type, &desc.size);
+		enum object_type type;
+		void *data = read_sha1_file(sha1, &type, &desc.size);
 		if (!data) {
 			tree->object.flags |= INCOMPLETE;
 			return 0;