core: Re-unify on one OSTREE_OBJECT_TYPE_FILE

Having the archived vs not distinction in the object system wasn't
useful in light of pack files.  In fact, we should probably move
towards generating a pack file per commit by default.

src/libotutil/ot-gio-utils.h

@@ -61,6 +61,14 @@ gboolean ot_gfile_load_contents_utf8 (GFile         *file,
                                       GCancellable  *cancellable,
                                       GError       **error);
 
+gboolean ot_gio_write_update_checksum (GOutputStream  *out,
+                                       gconstpointer   data,
+                                       gsize           len,
+                                       gsize          *out_bytes_written,
+                                       GChecksum      *checksum,
+                                       GCancellable   *cancellable,
+                                       GError        **error);
+
 gboolean ot_gio_splice_get_checksum (GOutputStream  *out,
                                      GInputStream   *in,
                                      guchar        **out_csum,