core: Add size information to commit metadata

Add a --generate-sizes option to commit to add size information to the
commit metadata.  This will be used by higher level code which wants
to determine the total size necessary for downloading.

src/libostree/ostree-repo-private.h

@@ -24,6 +24,8 @@
 
 G_BEGIN_DECLS
 
+#define _OSTREE_OBJECT_SIZES_ENTRY_SIGNATURE "ay"
+
 /**
  * OstreeRepo:
  *
@@ -57,10 +59,12 @@ struct OstreeRepo {
   gboolean in_transaction;
   GHashTable *loose_object_devino_hash;
   GHashTable *updated_uncompressed_dirs;
+  GHashTable *object_sizes;
 
   GKeyFile *config;
   OstreeRepoMode mode;
   gboolean enable_uncompressed_cache;
+  gboolean generate_sizes;
 
   OstreeRepo *parent_repo;
 };