pull: Add a --dry-run option for static deltas

One of the design goals with deltas was not just wire efficiency,
but also having all the data up front about how much data would
be transferred before starting.

Let's expose that better by adding a `dry-run` option to the pull API.
This requires static deltas to be useful.  Basically we simply call
the progress callback once with the data from the superblock.

src/libostree/ostree-repo-pull.c

@@ -48,6 +48,8 @@ typedef struct {
   GCancellable *cancellable;
   OstreeAsyncProgress *progress;
 
+  gboolean      dry_run;
+  gboolean      dry_run_emitted_progress;
   gboolean      legacy_transaction_resuming;
   enum {
     OSTREE_PULL_PHASE_FETCHING_REFS,
@@ -78,6 +80,7 @@ typedef struct {
   guint             n_outstanding_deltapart_write_requests;
   guint             n_total_deltaparts;
   guint64           total_deltapart_size;
+  guint64           total_deltapart_usize;
   gint              n_requested_metadata;
   gint              n_requested_content;
   guint             n_fetched_deltaparts;
@@ -227,6 +230,8 @@ update_progress (gpointer user_data)
                                   pull_data->n_total_deltaparts);
   ostree_async_progress_set_uint64 (pull_data->progress, "total-delta-part-size",
                                     pull_data->total_deltapart_size);
+  ostree_async_progress_set_uint64 (pull_data->progress, "total-delta-part-usize",
+                                    pull_data->total_deltapart_usize);
   ostree_async_progress_set_uint (pull_data->progress, "total-delta-superblocks",
                                   pull_data->static_delta_superblocks->len);
 
@@ -243,6 +248,9 @@ update_progress (gpointer user_data)
   else
     ostree_async_progress_set_status (pull_data->progress, NULL);
 
+  if (pull_data->dry_run)
+    pull_data->dry_run_emitted_progress = TRUE;
+
   return TRUE;
 }
 
@@ -262,6 +270,9 @@ pull_termination_condition (OtPullData          *pull_data)
   if (pull_data->caught_error)
     return TRUE;
 
+  if (pull_data->dry_run)
+    return pull_data->dry_run_emitted_progress;
+
   switch (pull_data->phase)
     {
     case OSTREE_PULL_PHASE_FETCHING_REFS:
@@ -1451,11 +1462,18 @@ process_one_static_delta_fallback (OtPullData   *pull_data,
   if (!ostree_validate_structureof_csum_v (csum_v, error))
     goto out;
 
+  pull_data->total_deltapart_size += compressed_size;
+  pull_data->total_deltapart_usize += uncompressed_size;
+
+  if (pull_data->dry_run)
+    {
+      ret = TRUE;
+      goto out;
+    }
+
   objtype = (OstreeObjectType)objtype_y;
   checksum = ostree_checksum_from_bytes_v (csum_v);
 
-  pull_data->total_deltapart_size += compressed_size;
-
   if (!ostree_repo_has_object (pull_data->repo, objtype, checksum,
                                &is_stored,
                                cancellable, error))
@@ -1524,6 +1542,7 @@ process_one_static_delta (OtPullData   *pull_data,
     }
 
   /* Write the to-commit object */
+  if (!pull_data->dry_run)
   {
     g_autoptr(GVariant) to_csum_v = NULL;
     g_autofree char *to_checksum = NULL;
@@ -1626,7 +1645,11 @@ process_one_static_delta (OtPullData   *pull_data,
       }
 
       pull_data->total_deltapart_size += size;
+      pull_data->total_deltapart_usize += usize;
 
+      if (pull_data->dry_run)
+        continue;
+      
       fetch_data = g_new0 (FetchStaticDeltaData, 1);
       fetch_data->pull_data = pull_data;
       fetch_data->objects = g_variant_ref (objects);
@@ -1780,6 +1803,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
       (void) g_variant_lookup (options, "disable-static-deltas", "b", &disable_static_deltas);
       (void) g_variant_lookup (options, "require-static-deltas", "b", &require_static_deltas);
       (void) g_variant_lookup (options, "override-commit-ids", "^a&s", &override_commit_ids);
+      (void) g_variant_lookup (options, "dry-run", "b", &pull_data->dry_run);
     }
 
   g_return_val_if_fail (pull_data->maxdepth >= -1, FALSE);
@@ -1790,6 +1814,10 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
     g_return_val_if_fail (dir_to_pull[0] == '/', FALSE);
 
   g_return_val_if_fail (!(disable_static_deltas && require_static_deltas), FALSE);
+  /* We only do dry runs with static deltas, because we don't really have any
+   * in-advance information for bare fetches.
+   */
+  g_return_val_if_fail (!pull_data->dry_run || require_static_deltas, FALSE);
 
   pull_data->is_mirror = (flags & OSTREE_REPO_PULL_FLAGS_MIRROR) > 0;
   pull_data->is_commit_only = (flags & OSTREE_REPO_PULL_FLAGS_COMMIT_ONLY) > 0;
@@ -2243,7 +2271,7 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
 
   if (pull_data->progress)
     {
-      update_timeout = g_timeout_source_new_seconds (1);
+      update_timeout = g_timeout_source_new_seconds (pull_data->dry_run ? 0 : 1);
       g_source_set_priority (update_timeout, G_PRIORITY_HIGH);
       g_source_set_callback (update_timeout, update_progress, pull_data, NULL);
       g_source_attach (update_timeout, pull_data->main_context);
@@ -2256,6 +2284,12 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
 
   if (pull_data->caught_error)
     goto out;
+
+  if (pull_data->dry_run)
+    {
+      ret = TRUE;
+      goto out;
+    }
   
   g_assert_cmpint (pull_data->n_outstanding_metadata_fetches, ==, 0);
   g_assert_cmpint (pull_data->n_outstanding_metadata_write_requests, ==, 0);