The update works by checking the local packages folder for updates, and applying those that are not yet applied. The change is made using delta changes, which is why the files are so small.

The reason that we add the changes to source control is so that they are pushed to other developers and also to the build. Once a hotfix has been added to TFS, the resulting deployable package increases in size from a few megabytes to around 600 MB. This is because packages must be deployed in total.

We have to manually add the model descriptor file to TFS if we want the build server to build the package. This is used by the build server to work out what needs to be built, and what will end up as a build artefact against the build. Should we add model descriptor files for models that are not in TFS, errors will be produced; this is solved by removing the file from TFS.