TFS online: how to ignore packages (nuget)

If you want to avoid checking in NuGet packages into your source control system; you have to introduce a .tfignore file into the system.

1. Create a text file: tfignore.txt
2. Place it next to your solution file
3. Open the file and add \packages as the only content
4. Open the folder in a command prompt (cmd)
5. rename the file by typing: ren tfignore.txt .tfignore
6. check the file into source control
7. TFS now no longer regards this folder (\packages) as valid content