object-file.c: use size_t for header lengths

Continue walking the code path for the >4GB `hash-object --literally`
test. The `hash_object_file_literally()` function internally uses both
`hash_object_file()` and `write_object_file_prepare()`. Both function
signatures use `unsigned long` rather than `size_t` for the mem buffer
sizes. Use `size_t` instead, for LLP64 compatibility.

While at it, convert those function's object's header buffer length to
`size_t` for consistency. The value is already upcast to `uintmax_t` for
print format compatibility.

Note: The hash-object test still does not pass. A subsequent commit
continues to walk the call tree's lower level hash functions to identify
further fixes.

Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: PhilipOakley

object-file.c

@@ -318,7 +318,7 @@ int parse_loose_header(const char *hdr, struct object_info *oi)
 static void hash_object_body(const struct git_hash_algo *algo, struct git_hash_ctx *c,
 			     const void *buf, unsigned long len,
 			     struct object_id *oid,
-			     char *hdr, int *hdrlen)
+			     char *hdr, size_t *hdrlen)
 {
 	algo->init_fn(c);
 	git_hash_update(c, hdr, *hdrlen);
@@ -327,9 +327,9 @@ static void hash_object_body(const struct git_hash_algo *algo, struct git_hash_c
 }
 
 void write_object_file_prepare(const struct git_hash_algo *algo,
-			       const void *buf, unsigned long len,
+			       const void *buf, size_t len,
 			       enum object_type type, struct object_id *oid,
-			       char *hdr, int *hdrlen)
+			       char *hdr, size_t *hdrlen)
 {
 	struct git_hash_ctx c;
 
@@ -472,11 +472,11 @@ int finalize_object_file_flags(struct repository *repo,
 }
 
 void hash_object_file(const struct git_hash_algo *algo, const void *buf,
-		      unsigned long len, enum object_type type,
+		      size_t len, enum object_type type,
 		      struct object_id *oid)
 {
 	char hdr[MAX_HEADER_LEN];
-	int hdrlen = sizeof(hdr);
+	size_t hdrlen = sizeof(hdr);
 
 	write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
 }

object-file.h

@@ -131,12 +131,12 @@ int finalize_object_file_flags(struct repository *repo,
 			       enum finalize_object_file_flags flags);
 
 void hash_object_file(const struct git_hash_algo *algo, const void *buf,
-		      unsigned long len, enum object_type type,
+		      size_t len, enum object_type type,
 		      struct object_id *oid);
 void write_object_file_prepare(const struct git_hash_algo *algo,
-			       const void *buf, unsigned long len,
+			       const void *buf, size_t len,
 			       enum object_type type, struct object_id *oid,
-			       char *hdr, int *hdrlen);
+			       char *hdr, size_t *hdrlen);
 int write_loose_object(struct odb_source_loose *loose,
 		       const struct object_id *oid, char *hdr,
 		       int hdrlen, const void *buf, unsigned long len,