Comparing With Branch
In addition to the common ways to compare file versions, you can use the special command that lets you compare a file from your local working copy with its version in the selected branch.
Select the desired file in the Project Tool Window, or open it in the editor.
From the main VCS menu, or the context menu of the selection, choose Subversion | Compare with Branch.
In the Compare with Branch popup, select the desired branch. The Compare with Branch dialog in the form of the Differences viewer for files appears.