@Override
    public @Nullable VcsFileRevision getPreviousRevision(int lineNumber) {
      LineInfo lineInfo = getLineInfo(lineNumber);
      if (lineInfo == null) return null;

      VcsFileRevision previousFileRevision = lineInfo.getPreviousFileRevision();
      if (previousFileRevision != null) return previousFileRevision;

      GitRevisionNumber revisionNumber = lineInfo.getRevisionNumber();
      if (myRevisions != null && myRevisionMap != null &&
          myRevisionMap.containsKey(revisionNumber)) {
        int index = myRevisionMap.getInt(revisionNumber);
        if (index + 1 < myRevisions.size()) {
          return myRevisions.get(index + 1);
        }
      }

      return null;
    }
@Override
    public @Nullable VcsFileRevision getPreviousRevision(int lineNumber)