message: Minor simplification to Mesh::CreatePeriodicVertexMapping
diff: @@ -4506,6 +4506,7 @@ std::vector<int> Mesh::CreatePeriodicVertexMapping(
  // list of masters.
  auto make_master_slave = [&slaves,&masters](int m1, int m2)
  {
  + if (m1 == m2) { return; }
  masters[m2].insert(m1);
  slaves[m1] = m2;
  for (int s : masters[m1])
  @@ -4549,23 +4550,17 @@ std::vector<int> Mesh::CreatePeriodicVertexMapping(
  {
  // `master` is already a master and `slave` is already a slave
  int master_of_slave = slaves[slave];
  - if (master != master_of_slave)
  - {
  // Make `master` and its slaves slaves of `slave`'s master
  make_master_slave(master, master_of_slave);
  }
  - }
  else if (!mInM && sInM)
  {
  // `master` is currently a slave and
  // `slave` is currently a master
  // Make `slave` and its slaves slaves of `master`'s master
  int master_of_master = slaves[master];
  - if (slave != master_of_master)
  - {
  make_master_slave(slave, master_of_master);
  }
  - }
  else
  {
  // Both vertices are currently slaves
  @@ -4573,11 +4568,8 @@ std::vector<int> Mesh::CreatePeriodicVertexMapping(
  int master_of_master = slaves[master];
  int master_of_slave = slaves[slave];
  // Move slave and its fellow slaves to master_of_master
  - if (master_of_master != master_of_slave)
  - {
  make_master_slave(master_of_slave, master_of_master);
  }
  - }
  break;
  }
  }
  