When mirroring, write content directly, do not verify

When doing a pull --mirror from an archive-z2 repository into another
archive-z2 repository, currently we gunzip/checksum/gzip each content
object.  The re-gzip process in particular is fairly expensive.

This does assume that the upstream content is trusted and correct.
It'd be nice in the future to do at least a CRC check, if not the full
checksum.  (Could we append CRC data to the end of filez objects?)

We could also choose to only do this optimization if fetching over
TLS.

before: 1626 metadata, 20320 content objects fetched; 299634 KiB transferred in 62 seconds
after : 1626 metadata, 20320 content objects fetched; 299634 KiB transferred in 11 seconds

src/libostree/ostree-repo-pull.c

@@ -82,6 +82,8 @@ typedef struct {
   int               maxdepth;
   guint64           start_time;
 
+  gboolean          is_mirror;
+
   char         *dir;
   gboolean      commitpartial_exists;
 
@@ -596,32 +598,54 @@ content_fetch_on_complete (GObject        *object,
   g_assert (objtype == OSTREE_OBJECT_TYPE_FILE);
 
   g_debug ("fetch of %s complete", ostree_object_to_string (checksum, objtype));
-  
-  if (!ostree_content_file_parse_at (TRUE, pull_data->tmpdir_dfd, temp_path, FALSE,
-                                     &file_in, &file_info, &xattrs,
-                                     cancellable, error))
+
+  if (pull_data->is_mirror && pull_data->repo->mode == OSTREE_REPO_MODE_ARCHIVE_Z2)
     {
-      /* If it appears corrupted, delete it */
-      (void) unlinkat (pull_data->tmpdir_dfd, temp_path, 0);
-      goto out;
+      gboolean have_object;
+      if (!ostree_repo_has_object (pull_data->repo, OSTREE_OBJECT_TYPE_FILE, checksum,
+                                   &have_object,
+                                   cancellable, error))
+        goto out;
+
+      if (!have_object)
+        {
+          if (!_ostree_repo_commit_loose_final (pull_data->repo, checksum, OSTREE_OBJECT_TYPE_FILE,
+                                                pull_data->tmpdir_dfd, temp_path,
+                                                cancellable, error))
+            goto out;
+        }
+      pull_data->n_fetched_content++;
     }
+  else
+    {
+      /* Non-mirroring path */
+      
+      if (!ostree_content_file_parse_at (TRUE, pull_data->tmpdir_dfd, temp_path, FALSE,
+                                         &file_in, &file_info, &xattrs,
+                                         cancellable, error))
+        {
+          /* If it appears corrupted, delete it */
+          (void) unlinkat (pull_data->tmpdir_dfd, temp_path, 0);
+          goto out;
+        }
 
-  /* Also, delete it now that we've opened it, we'll hold
-   * a reference to the fd.  If we fail to write later, then
-   * the temp space will be cleaned up.
-   */
-  (void) unlinkat (pull_data->tmpdir_dfd, temp_path, 0);
-
-  if (!ostree_raw_file_to_content_stream (file_in, file_info, xattrs,
-                                          &object_input, &length,
-                                          cancellable, error))
-    goto out;
+      /* Also, delete it now that we've opened it, we'll hold
+       * a reference to the fd.  If we fail to write later, then
+       * the temp space will be cleaned up.
+       */
+      (void) unlinkat (pull_data->tmpdir_dfd, temp_path, 0);
+      
+      if (!ostree_raw_file_to_content_stream (file_in, file_info, xattrs,
+                                              &object_input, &length,
+                                              cancellable, error))
+        goto out;
   
-  pull_data->n_outstanding_content_write_requests++;
-  ostree_repo_write_content_async (pull_data->repo, checksum,
-                                   object_input, length,
-                                   cancellable,
-                                   content_fetch_on_write_complete, fetch_data);
+      pull_data->n_outstanding_content_write_requests++;
+      ostree_repo_write_content_async (pull_data->repo, checksum,
+                                       object_input, length,
+                                       cancellable,
+                                       content_fetch_on_write_complete, fetch_data);
+    }
 
  out:
   pull_data->n_outstanding_content_fetches--;
@@ -1589,7 +1613,6 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
   OstreeRepoPullFlags flags = 0;
   const char *dir_to_pull = NULL;
   char **refs_to_fetch = NULL;
-  gboolean is_mirror;
   GSource *update_timeout = NULL;
   GSource *idle_src;
 
@@ -1609,7 +1632,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
   if (dir_to_pull)
     g_return_val_if_fail (dir_to_pull[0] == '/', FALSE);
 
-  is_mirror = (flags & OSTREE_REPO_PULL_FLAGS_MIRROR) > 0;
+  pull_data->is_mirror = (flags & OSTREE_REPO_PULL_FLAGS_MIRROR) > 0;
 
   pull_data->async_error = error;
   pull_data->main_context = g_main_context_ref_thread_default ();
@@ -1824,7 +1847,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
 
   pull_data->static_delta_superblocks = g_ptr_array_new_with_free_func ((GDestroyNotify)g_variant_unref);
 
-  if (is_mirror && !refs_to_fetch && !configured_branches)
+  if (pull_data->is_mirror && !refs_to_fetch && !configured_branches)
     {
       SoupURI *summary_uri = NULL;
       gs_unref_bytes GBytes *bytes = NULL;
@@ -2034,7 +2057,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
         }
       else
         {
-          ostree_repo_transaction_set_ref (pull_data->repo, is_mirror ? NULL : pull_data->remote_name, ref, checksum);
+          ostree_repo_transaction_set_ref (pull_data->repo, pull_data->is_mirror ? NULL : pull_data->remote_name, ref, checksum);
         }
     }