I have been using BBEdit as my external diff but it is not possible to tell it to ignore whitespace when it is launched from SourceTree.

I have tried setting the visual diff tool to "Other..." and then putting bbdiff and $REMOTE $LOCAL in the boxes, but while this does create the temp file for comparing, it does not seem to do anything else. Certainly, it does not diff in BBEdit. It fails regardless of whether I add "-ignore-spaces" or any other args like "-wait --reverse --resume".

Is there a way to make this happen, please? Thanks.

Also, this is marked as "Minor" now and I can understand that it might seem so - unless you are the person trying to figure out what the actual change was in a file that has been reformatted.  Code reviews become exponentially harder.  Thanks for whatever attention this can get - or even a hint about how a workaround could be done using bbdiff and the "Other..." menu choice.