completely forgot the patch format required!

[Jim - FooBar();]

how should I produce my patch? I'm guessing a mere diff won't do the 
job. I think I've bitten in the past and so this has probably been 
answered before but I 've now spent 25 min going through my email 
history and cannot find anything related...suppose I've got the 2 files 
in the same directory, f1.java & f2.java...what is the command to 
produce the patch?

thanks,
Jim