This tidbit just came across my email and I know that I’m going to need it sometime in the future, so I’m blogging it for posterity.
The MSBuild and XAML build systems found in the Team Build feature of TFS and VSO have provided the ability to set the output logging level so that your logs would return excruciatingly detailed logs of every action in the build process. This facility was implemented as a Property in MSBuild builds (/p:verbosity=diagnostic) and as a setting in the XAML build system (2. Basic -> Logging verbosity -> Detailed). In the new build system in VSO and TFS 2015 there is no setting for this value.
To make the new build system return detailed log files you need to add a new variable to your Build Definition called system.debug with a value of true.
Happy building! 🙂