read-cache.c: make create_from_disk() report number of bytes it consumed

The function is the one that is reading from the data stream. It only is
natural to make it responsible for reporting this number, not the caller.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

read-cache.c

@@ -1305,7 +1305,8 @@ static inline uint32_t ntoh_l_force_align(void *p)
 #define ntoh_l(var) ntoh_l_force_align(&(var))
 #endif
 
-static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
+static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk,
+					    unsigned long *ent_size)
 {
 	struct cache_entry *ce;
 	size_t len;
@@ -1351,6 +1352,7 @@ static struct cache_entry *create_from_disk(struct ondisk_cache_entry *ondisk)
 
 	memcpy(ce->name, name, len);
 	ce->name[len] = '\0';
+	*ent_size = ondisk_ce_size(ce);
 	return ce;
 }
 
@@ -1404,12 +1406,13 @@ int read_index_from(struct index_state *istate, const char *path)
 	for (i = 0; i < istate->cache_nr; i++) {
 		struct ondisk_cache_entry *disk_ce;
 		struct cache_entry *ce;
+		unsigned long consumed;
 
 		disk_ce = (struct ondisk_cache_entry *)((char *)mmap + src_offset);
-		ce = create_from_disk(disk_ce);
+		ce = create_from_disk(disk_ce, &consumed);
 		set_index_entry(istate, i, ce);
 
-		src_offset += ondisk_ce_size(ce);
+		src_offset += consumed;
 	}
 	istate->timestamp.sec = st.st_mtime;
 	istate->timestamp.nsec = ST_MTIME_NSEC(st);