message: don't stay broken if we get bad state into git-indexer's meta
diff: @@ -71,8 +71,12 @@ class GitUpdater {
  await this._loadCommit();
  let originalTree;
  if (meta && meta.commit) {
  + try {
  let oldCommit = await Commit.lookup(this.repo, meta.commit);
  originalTree = await oldCommit.getTree();
  + } catch (err) {
  + this.log.warn(`Unable to load previously indexed commit ${meta.commit} due to ${err}. We will recover by reindexing all content.`);
  + }
  }
  await this._indexTree(ops, originalTree, this.rootTree, {
  only: this.basePath.concat([['schema', 'contents']])
  