Quickly and easily compare all files in Git (a commit or Staged/Unstaged files) or TFS (a changeset, shelveset, or files with pending changes) to see what has changed. Instead of clicking on each file individually and choosing to compare it with a different version, just click one button to compare all of the files.
You may edit the extension's settings from the Tools -> Options... -> Diff All Files settings page.
Download this extension for Visual Studio 2012, 2013, or 2015 from the VS Extension Gallery.
Before comparing files (left) and while comparing files (right):
Settings Screen (available in Visual Studio from Tools -> Options... -> Diff All Files):