How can I plug FileMerge into my Source Control App I'd like to use FileMerge (Version 2.8) as Git and Perforce's Diff viewer, however whenever one of these apps tries to do a diff I get this message:



This isn't just for Groovy files either,it's for any type of file I try to run a diff against.  This is happening on systems running 10.9 and 10.8.  

This is how I have it configured in Perforce:
The issue is that you are setting an app bundle in the config when the version control program is expecing a Unix command line.

You should use /usr/bin/opendiff as the command line. I think that is the only chnage you need for the perforce diff you show.

Example git configs for merging are in this  question and several other duplicates on StackOverflow.