message: Notes on updating
diff: @@ -16,6 +16,13 @@ The Visionaray git repository can be cloned using the following commands:
  git clone --recursive https://github.com/szellmann/visionaray.git
  ```
  +An existing working copy can be updated using the following commands:
  +
  +```Shell
  +git submodule sync
  +git submodule update --init --recursive
  +```
  +
  Build requirements
  ------------------
  