message: [doc] GetBestBlock() doesn't do nothing
  This has tripped people up multiple times because it looks like
  GetBestBlock is a const function returning the value of hashBlock.
diff: @@ -630,7 +630,8 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
  }
  }
  - // Bring the best block into scope
  + // This is const, but calls into the back end CoinsViews. The CCoinsViewDB at the bottom of the
  + // hierarchy brings the best block into scope. See CCoinsViewDB::GetBestBlock().
  m_view.GetBestBlock();
  // we have all inputs cached now, so switch back to dummy (to protect
  