First confirm that /usr/local/bin/diffmerge is present.
If you used the PKG Installer, this was installed
when /Applications/DiffMerge.app was installed.
If you used the DMG file, refer to the instructions for installing the
Extras.
Add the following lines to your .hgrc:
[extensions] hgext.extdiff = [extdiff] cmd.diffmerge = /usr/local/bin/diffmerge [merge-tools] diffmerge.executable = /usr/local/bin/diffmerge diffmerge.args = --result=$output $local $base $other diffmerge.binary = False diffmerge.symlinks = False diffmerge.gui = True diffmerge.premerge = True
