Use GNU diff instead of Solaris diff.
Solaris diff doesn't understand the -N option, which is part of the default
option set.
This is a very Solaris-specific patch, and should not be passed upstream.
diff --git a/hgext/extdiff.py b/hgext/extdiff.py
@@ -282,7 +282,7 @@ def extdiff(ui, repo, *pats, **opts):
program = opts.get('program')
option = opts.get('option')
if not program:
- program = 'diff'
+ program = 'gdiff'
option = option or ['-Npru']
cmdline = ' '.join(map(util.shellquote, [program] + option))
return dodiff(ui, repo, cmdline, pats, opts)