private @Nullable String getRecentCommonBranch() {
    String recentCommonBranch = null;
    for (String branch : myCurrentHeads.values()) {
      if (recentCommonBranch == null) {
        recentCommonBranch = branch;
      }
      else if (!recentCommonBranch.equals(branch)) {
        return null;
      }
    }
    return recentCommonBranch;
  }
private @Nullable String getRecentCommonBranch()