Add an archive-z repository mode

This is where loose content objects are stored as one compressed file,
instead of the two separate ones for regular archive mode.  This mode
would be suitable for HTTP servers, beause only one HTTP request is
necessary, and the result would be compressed.

src/libostree/ostree-core.c

@@ -471,6 +471,34 @@ ostree_content_stream_parse (GInputStream           *input,
 
 }
 
+gboolean
+ostree_zlib_content_stream_open (GInputStream           *input,
+                                 guint64                *out_len,
+                                 GInputStream          **out_uncompressed,
+                                 GCancellable           *cancellable,
+                                 GError                **error)
+{
+  gboolean ret = FALSE;
+  guint64 uncompressed_len;
+  ot_lobj GConverter *zlib_decomp = NULL;
+  ot_lobj GInputStream *uncomp_input = NULL;
+
+  if (!g_input_stream_read_all (input, &uncompressed_len, sizeof (guint64),
+                                NULL, cancellable, error))
+    goto out;
+
+  uncompressed_len = GUINT64_FROM_BE (uncompressed_len);
+  zlib_decomp = (GConverter*)g_zlib_decompressor_new (G_ZLIB_COMPRESSOR_FORMAT_RAW);
+  uncomp_input = g_converter_input_stream_new (input, zlib_decomp);
+
+  if (out_len)
+    *out_len = uncompressed_len;
+  ot_transfer_out_value (out_uncompressed, &uncomp_input);
+  ret = TRUE;
+ out:
+  return ret;
+}
+
 gboolean
 ostree_content_file_parse (GFile                  *content_path,
                            gboolean                trusted,
@@ -909,8 +937,9 @@ ostree_checksum_bytes_peek (GVariant *bytes)
 }
 
 char *
-ostree_get_relative_object_path (const char *checksum,
-                                 OstreeObjectType type)
+ostree_get_relative_object_path (const char         *checksum,
+                                 OstreeObjectType    type,
+                                 gboolean            compressed)
 {
   GString *path;
 
@@ -923,6 +952,8 @@ ostree_get_relative_object_path (const char *checksum,
   g_string_append (path, checksum + 2);
   g_string_append_c (path, '.');
   g_string_append (path, ostree_object_type_to_string (type));
+  if (!OSTREE_OBJECT_TYPE_IS_META (type) && compressed)
+    g_string_append (path, "z");
 
   return g_string_free (path, FALSE);
 }