Problem

The FileMerge option cannot be performed.

Diagnosis

Environment

• Mac OS X 10.7 - Lion
• Xcode 4.2

Cause

When installing Xcode 4.2, the opendiff command line tool is moved from /usr/bin to /Developer/usr/bin. However, the path to the command is not added to the PATH list and this causes to command to fail.

Resolution options

Resolution 1

Create a symbolic link to the new location of the opendiff command

sudo ln -s /Developer/usr/bin/opendiff /usr/bin/opendiff

Resolution 2

Add /Developer/usr/bin to your path. You will need to do this in two locations:

1. /etc/paths - this is the $PATH that the SourceTree user interface uses (Note: a computer restart may be required for this change to be effective)
2. Your ~/.bash_profile or similar

Additional resolution option

It may still occur, that the command is still failing after having applied one of the option above.

If this is the case, try running the opendiff command from the command line, in case you get a response like the following:

xcode-select: Error: No Xcode folder is set. Run xcode-select -switch <xcode_folder_path> to set the path to the Xcode folder.
Error: /usr/bin/xcode-select returned unexpected error.

sudo xcode-select -switch /Developer