This tag corresponds to the version of MSBuild packaged with Visual Studio 2015 Update 2.
This release is also available through the standalone Build Tools 2015 with Update 2 installer.
Important: the actual Update 2 release was not produced by compiling the GitHub source at this commit. It was built from a mirror of MSBuild in the Microsoft-internal VS repository, which was manually synced to contain the changes made here. These sources are instructive for behavior and understanding purposes, but not suitable for debugging the released binaries.