lib/pull: Honor requiring static deltas for scratch delta

If a scratch delta exists and the caller has required static deltas, use
it instead of the heuristic about existing commits.

src/libostree/ostree-repo-pull.c

@@ -3455,10 +3455,10 @@ initiate_request (OtPullData                 *pull_data,
              * the ref already exists locally, since we are likely only a few
              * commits out of date; so doing an object pull is likely more
              * bandwidth efficient. */
-            if (delta_from_revision != NULL)
-              queue_scan_one_metadata_object (pull_data, to_revision, OSTREE_OBJECT_TYPE_COMMIT, NULL, 0, ref);
-            else
+            if (pull_data->require_static_deltas || delta_from_revision == NULL)
               enqueue_one_static_delta_superblock_request (pull_data, NULL, to_revision, ref);
+            else
+              queue_scan_one_metadata_object (pull_data, to_revision, OSTREE_OBJECT_TYPE_COMMIT, NULL, 0, ref);
           }
           break;
         case DELTA_SEARCH_RESULT_UNCHANGED:

tests/pull-test.sh

@@ -639,8 +639,16 @@ if ${CMD_PREFIX} ostree --repo=repo pull origin scratch 2>err.txt; then
 fi
 assert_file_has_content err.txt "Invalid checksum for static delta"
 
-# Fully pull the parent commit then pull the HEAD. This should succeed
-# with an object pull.
+# Fully pull the parent commit then pull the HEAD with
+# --require-static-deltas. This should succeed with an object pull.
+${CMD_PREFIX} ostree --repo=repo pull origin scratch@${old_rev}
+if ${CMD_PREFIX} ostree --repo=repo pull --require-static-deltas origin scratch 2>err.txt; then
+    assert_not_reached "pull of corrupt scratch delta unexpectedly succeeded"
+fi
+assert_file_has_content err.txt "Invalid checksum for static delta"
+
+# Pull the HEAD again without --require-static-deltas. This should
+# succeed with an object pull.
 ${CMD_PREFIX} ostree --repo=repo pull origin scratch@${old_rev}
 ${CMD_PREFIX} ostree --repo=repo pull origin scratch
 ${CMD_PREFIX} ostree --repo=repo fsck