Error when using the patch with mac El Captian

[mattj83]

I attempted to use the patch and I get the following error
diff: unrecognized option --git' diff: Trydiff --help' for more information.
/usr/local/bin/csshX: line 2: index: command not found
/usr/local/bin/csshX: line 3: ---: command not found
/usr/local/bin/csshX: line 4: +++: command not found
/usr/local/bin/csshX: line 5: @@: command not found
/usr/local/bin/csshX: line 6: syntax error near unexpected token (' /usr/local/bin/csshX: line 6: return [ map { expand_hostrange($to_repeat) || $to_repeat } (1..$2) ];'
zsh: permission denied: /Users/mattjohnson/.ssh/nibiruv2.pem

I used this with a pem file, that is csshX @;

Thanks in advance for any help.