The 'Repository' tab in the Changes Window seems to have trouble with the first modification of a file in a branch. It doesn't think there's a previous version to diff against - so the diffs are useless. It shows the whole file was added instead of diff'ing against the version of the file that the branch version was created off of.
Example: I create a branch at file version 1.6. This creates branch version 1.6.2. I check in a change to the file to create version 126.96.36.199. In the 'Repository' Tab of the Changes Window I see my checkin comments and file. The file name is green - indicating IntelliJ thinks it was a new file added with the checkin. Asking for a file diff to show what changed with the checkin produces a diff showing the whole file was added. On the right it shows the entire version 188.8.131.52 of the file while on the left it's an empty pane. It doesn't seem to know to diff against version 1.6 of the file to discover the actual difference.
Is this supposed to work? Maybe I have something stange with my project setup.