Don't lie that "binary file has changed"

Without -a option to "hg diff", mdiff.unidiff reported that "Binary
file foo has changed" without even trying to compare things. Now it
computes MD5 of old and new files, compares them and makes the conclusion.

mercurial/mdiff.py

@@ -1,252 +1,257 b''
 # mdiff.py - diff and patch routines for mercurial
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
 from demandload import demandload
 import bdiff, mpatch
-demandload(globals(), "re struct util")
+demandload(globals(), "re struct util md5")
 
 def splitnewlines(text):
     '''like str.splitlines, but only split on newlines.'''
     lines = [l + '\n' for l in text.split('\n')]
     if lines:
         if lines[-1] == '\n':
             lines.pop()
         else:
             lines[-1] = lines[-1][:-1]
     return lines
 
 class diffopts(object):
     '''context is the number of context lines
     text treats all files as text
     showfunc enables diff -p output
     git enables the git extended patch format
     nodates removes dates from diff headers
     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,
         'git': False,
         'nodates': False,
         '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):
     def datetag(date):
         return (opts.git or opts.nodates) and '\n' or '\t%s\n' % date
 
     if not a and not b: return ""
     epoch = util.datestr((0, 0))
 
     if not opts.text and (util.binary(a) or util.binary(b)):
+        def h(v):
+            # md5 is used instead of sha1 because md5 is supposedly faster
+            return md5.new(v).digest()
+        if a and b and len(a) == len(b) and h(a) == h(b):
+            return ""
         l = ['Binary file %s has changed\n' % fn]
     elif not a:
         b = splitnewlines(b)
         if a is None:
             l1 = '--- /dev/null%s' % datetag(epoch)
         else:
             l1 = "--- %s%s" % ("a/" + fn, datetag(ad))
         l2 = "+++ %s%s" % ("b/" + fn, datetag(bd))
         l3 = "@@ -0,0 +1,%d @@\n" % len(b)
         l = [l1, l2, l3] + ["+" + e for e in b]
     elif not b:
         a = splitnewlines(a)
         l1 = "--- %s%s" % ("a/" + fn, datetag(ad))
         if b is None:
             l2 = '+++ /dev/null%s' % datetag(epoch)
         else:
             l2 = "+++ %s%s" % ("b/" + fn, datetag(bd))
         l3 = "@@ -1,%d +0,0 @@\n" % len(a)
         l = [l1, l2, l3] + ["-" + e for e in a]
     else:
         al = splitnewlines(a)
         bl = splitnewlines(b)
         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%s" % (l[0][:-2], datetag(ad))
         l[1] = "%s%s" % (l[1][:-2], datetag(bd))
 
     for ln in xrange(len(l)):
         if l[ln][-1] != '\n':
             l[ln] += "\n\ No newline at end of file\n"
 
     if r:
         l.insert(0, "diff %s %s\n" %
                     (' '.join(["-r %s" % rev for rev in r]), fn))
 
     return "".join(l)
 
 # somewhat self contained replacement for difflib.unified_diff
 # 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
 def bunidiff(t1, t2, l1, l2, header1, header2, opts=defaultopts):
     def contextend(l, len):
         ret = l + opts.context
         if ret > len:
             ret = len
         return ret
 
     def contextstart(l):
         ret = l - opts.context
         if ret < 0:
             return 0
         return ret
 
     def yieldhunk(hunk, header):
         if header:
             for x in header:
                 yield x
         (astart, a2, bstart, b2, delta) = hunk
         aend = contextend(a2, len(l1))
         alen = aend - astart
         blen = b2 - bstart + aend - a2
 
         func = ""
         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):
                 t = l1[x].rstrip()
                 if funcre.match(t):
                     func = ' ' + t[:40]
                     break
 
         yield "@@ -%d,%d +%d,%d @@%s\n" % (astart + 1, alen,
                                            bstart + 1, blen, func)
         for x in delta:
             yield x
         for x in xrange(a2, aend):
             yield ' ' + l1[x]
 
     header = [ "--- %s\t\n" % header1, "+++ %s\t\n" % header2 ]
 
     if opts.showfunc:
         funcre = re.compile('\w')
     if opts.ignorewsamount:
         wsamountre = re.compile('[ \t]+')
         wsappendedre = re.compile(' \n')
     if opts.ignoreblanklines:
         wsblanklinesre = re.compile('\n')
     if opts.ignorews:
         wsre = re.compile('[ \t]')
 
     # bdiff.blocks gives us the matching sequences in the files.  The loop
     # below finds the spaces between those matching sequences and translates
     # them into diff output.
     #
     diff = bdiff.blocks(t1, t2)
     hunk = None
     for i in xrange(len(diff)):
         # The first match is special.
         # we've either found a match starting at line 0 or a match later
         # in the file.  If it starts later, old and new below will both be
         # empty and we'll continue to the next match.
         if i > 0:
             s = diff[i-1]
         else:
             s = [0, 0, 0, 0]
         delta = []
         s1 = diff[i]
         a1 = s[1]
         a2 = s1[0]
         b1 = s[3]
         b2 = s1[2]
 
         old = l1[a1:a2]
         new = l2[b1:b2]
 
         # bdiff sometimes gives huge matches past eof, this check eats them,
         # and deals with the special first match case described above
         if not old and not new:
             continue
 
         if opts.ignoreblanklines:
             wsold = wsblanklinesre.sub('', "".join(old))
             wsnew = wsblanklinesre.sub('', "".join(new))
             if wsold == wsnew:
                 continue
 
         if opts.ignorewsamount:
             wsold = wsamountre.sub(' ', "".join(old))
             wsold = wsappendedre.sub('\n', wsold)
             wsnew = wsamountre.sub(' ', "".join(new))
             wsnew = wsappendedre.sub('\n', wsnew)
             if wsold == wsnew:
                 continue
 
         if opts.ignorews:
             wsold = wsre.sub('', "".join(old))
             wsnew = wsre.sub('', "".join(new))
             if wsold == wsnew:
                 continue
 
         astart = contextstart(a1)
         bstart = contextstart(b1)
         prev = None
         if hunk:
             # join with the previous hunk if it falls inside the context
             if astart < hunk[1] + opts.context + 1:
                 prev = hunk
                 astart = hunk[1]
                 bstart = hunk[3]
             else:
                 for x in yieldhunk(hunk, header):
                     yield x
                 # we only want to yield the header if the files differ, and
                 # we only want to yield it once.
                 header = None
         if prev:
             # we've joined the previous hunk, record the new ending points.
             hunk[1] = a2
             hunk[3] = b2
             delta = hunk[4]
         else:
             # create a new hunk
             hunk = [ astart, a2, bstart, b2, delta ]
 
         delta[len(delta):] = [ ' ' + x for x in l1[astart:a1] ]
         delta[len(delta):] = [ '-' + x for x in old ]
         delta[len(delta):] = [ '+' + x for x in new ]
 
     if hunk:
         for x in yieldhunk(hunk, header):
             yield x
 
 def patchtext(bin):
     pos = 0
     t = []
     while pos < len(bin):
         p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
         pos += 12
         t.append(bin[pos:pos + l])
         pos += l
     return "".join(t)
 
 def patch(a, bin):
     return mpatch.patches(a, [bin])
 
 patches = mpatch.patches
 patchedsize = mpatch.patchedsize
 textdiff = bdiff.bdiff