Graphical multiple file-pair comparison on Mac OS 10.7

You could use Apple's FileMerge tool, or Kaleidoscope. Both of these have command-line invocations:

• to open FileMerge, install the command-line developer tools from inside Xcode and use opendiff
• to open Kaleidoscope, install its command-line tools from inside Kaleidoscope and use ksdiff

KDiff is an open source , visual text difference program. You can use it in windows,unix, linux and Mac OSX . Give it try. On windows , it automatically adds itself for svn diff. I do not use Mac OSX therefore can not say this function is also available there.

compares or merges two or three text input files or directories,

Following image url from kdiff3 site shows that it compare directories.