--- a/mercurial/mdiff.py
+++ b/mercurial/mdiff.py
@@ -19,14 +19,39 @@ def splitnewlines(text):
             lines[-1] = lines[-1][:-1]
     return lines
 
-def unidiff(a, ad, b, bd, fn, r=None, text=False,
-            showfunc=False, ignorews=False, ignorewsamount=False,
-            ignoreblanklines=False):
+class diffopts(object):
+    '''context is the number of context lines
+    text treats all files as text
+    showfunc enables diff -p output
+    ignorews ignores all whitespace changes in the diff
+    ignorewsamount ignores changes in the amount of whitespace
+    ignoreblanklines ignores changes whose lines are all blank'''
 
+    defaults = {
+        'context': 3,
+        'text': False,
+        'showfunc': True,
+        'ignorews': False,
+        'ignorewsamount': False,
+        'ignoreblanklines': False,
+        }
+
+    __slots__ = defaults.keys()
+
+    def __init__(self, **opts):
+        for k in self.__slots__:
+            v = opts.get(k)
+            if v is None:
+                v = self.defaults[k]
+            setattr(self, k, v)
+
+defaultopts = diffopts()
+
+def unidiff(a, ad, b, bd, fn, r=None, opts=defaultopts):
     if not a and not b: return ""
     epoch = util.datestr((0, 0))
 
-    if not text and (util.binary(a) or util.binary(b)):
+    if not opts.text and (util.binary(a) or util.binary(b)):
         l = ['Binary file %s has changed\n' % fn]
     elif not a:
         b = splitnewlines(b)
@@ -49,10 +74,7 @@ def unidiff(a, ad, b, bd, fn, r=None, te
     else:
         al = splitnewlines(a)
         bl = splitnewlines(b)
-        l = list(bunidiff(a, b, al, bl, "a/" + fn, "b/" + fn,
-                          showfunc=showfunc, ignorews=ignorews,
-                          ignorewsamount=ignorewsamount,
-                          ignoreblanklines=ignoreblanklines))
+        l = list(bunidiff(a, b, al, bl, "a/" + fn, "b/" + fn, opts=opts))
         if not l: return ""
         # difflib uses a space, rather than a tab
         l[0] = "%s\t%s\n" % (l[0][:-2], ad)
@@ -72,21 +94,15 @@ def unidiff(a, ad, b, bd, fn, r=None, te
 # t1 and t2 are the text to be diffed
 # l1 and l2 are the text broken up into lines
 # header1 and header2 are the filenames for the diff output
-# context is the number of context lines
-# showfunc enables diff -p output
-# ignorews ignores all whitespace changes in the diff
-# ignorewsamount ignores changes in the amount of whitespace
-# ignoreblanklines ignores changes whose lines are all blank
-def bunidiff(t1, t2, l1, l2, header1, header2, context=3, showfunc=False,
-             ignorews=False, ignorewsamount=False, ignoreblanklines=False):
+def bunidiff(t1, t2, l1, l2, header1, header2, opts=defaultopts):
     def contextend(l, len):
-        ret = l + context
+        ret = l + opts.context
         if ret > len:
             ret = len
         return ret
 
     def contextstart(l):
-        ret = l - context
+        ret = l - opts.context
         if ret < 0:
             return 0
         return ret
@@ -101,7 +117,7 @@ def bunidiff(t1, t2, l1, l2, header1, he
         blen = b2 - bstart + aend - a2
 
         func = ""
-        if showfunc:
+        if opts.showfunc:
             # walk backwards from the start of the context
             # to find a line starting with an alphanumeric char.
             for x in xrange(astart, -1, -1):
@@ -119,14 +135,14 @@ def bunidiff(t1, t2, l1, l2, header1, he
 
     header = [ "--- %s\t\n" % header1, "+++ %s\t\n" % header2 ]
 
-    if showfunc:
+    if opts.showfunc:
         funcre = re.compile('\w')
-    if ignorewsamount:
+    if opts.ignorewsamount:
         wsamountre = re.compile('[ \t]+')
         wsappendedre = re.compile(' \n')
-    if ignoreblanklines:
+    if opts.ignoreblanklines:
         wsblanklinesre = re.compile('\n')
-    if ignorews:
+    if opts.ignorews:
         wsre = re.compile('[ \t]')
 
     # bdiff.blocks gives us the matching sequences in the files.  The loop
@@ -159,13 +175,13 @@ def bunidiff(t1, t2, l1, l2, header1, he
         if not old and not new:
             continue
 
-        if ignoreblanklines:
+        if opts.ignoreblanklines:
             wsold = wsblanklinesre.sub('', "".join(old))
             wsnew = wsblanklinesre.sub('', "".join(new))
             if wsold == wsnew:
                 continue
 
-        if ignorewsamount:
+        if opts.ignorewsamount:
             wsold = wsamountre.sub(' ', "".join(old))
             wsold = wsappendedre.sub('\n', wsold)
             wsnew = wsamountre.sub(' ', "".join(new))
@@ -173,7 +189,7 @@ def bunidiff(t1, t2, l1, l2, header1, he
             if wsold == wsnew:
                 continue
 
-        if ignorews:
+        if opts.ignorews:
             wsold = wsre.sub('', "".join(old))
             wsnew = wsre.sub('', "".join(new))
             if wsold == wsnew:
@@ -184,7 +200,7 @@ def bunidiff(t1, t2, l1, l2, header1, he
         prev = None
         if hunk:
             # join with the previous hunk if it falls inside the context
-            if astart < hunk[1] + context + 1:
+            if astart < hunk[1] + opts.context + 1:
                 prev = hunk
                 astart = hunk[1]
                 bstart = hunk[3]