I know how to do this in SVN,
svn diff http://svn.example.com/branches/A/File1.txt http://svn.example.com/branches/B/File1.txt
But there has to
I find this method to be much easier:
Open the revision graph for the file you want to diff (context menu->TortoiseSVN->Revision Graph
). Select the first revision, and then control-click to select the second revision. Now right click on one of the selected revisions, and select Compare Revisions
from the context menu.
Tested on TortoiseSVN 1.7.6.
I don't know how new this feature is (I certainly read the documentation and didn't find it when I posted the question), but if you hold the Shift button down when you right click on a file, you can compare URLs without having to go to the repository browser.
See Difference to another branch/tag in the Viewing Differences documentation.
To illustrate: