filelog: allow censored files to contain padding data

To ensure delta compatibility, when a revision is censored, it is
padded to match the original data in size. The previous check does
not allow for padding because it was added before padding was found
to be a requirement.

For more background and design of the censorship feature, see:
mercurial.selenic.com/wiki/CensorPlan

mercurial/filelog.py

@@ -1,109 +1,109 b''
 # filelog.py - file history class for mercurial
 #
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import error, revlog
 import re
 
 _mdre = re.compile('\1\n')
 def parsemeta(text):
     """return (metadatadict, keylist, metadatasize)"""
     # text can be buffer, so we can't use .startswith or .index
     if text[:2] != '\1\n':
         return None, None
     s = _mdre.search(text, 2).start()
     mtext = text[2:s]
     meta = {}
     for l in mtext.splitlines():
         k, v = l.split(": ", 1)
         meta[k] = v
     return meta, (s + 2)
 
 def packmeta(meta, text):
     keys = sorted(meta.iterkeys())
     metatext = "".join("%s: %s\n" % (k, meta[k]) for k in keys)
     return "\1\n%s\1\n%s" % (metatext, text)
 
 def _censoredtext(text):
     m, offs = parsemeta(text)
-    return m and "censored" in m and not text[offs:]
+    return m and "censored" in m
 
 class filelog(revlog.revlog):
     def __init__(self, opener, path):
         super(filelog, self).__init__(opener,
                         "/".join(("data", path + ".i")))
 
     def read(self, node):
         t = self.revision(node)
         if not t.startswith('\1\n'):
             return t
         s = t.index('\1\n', 2)
         return t[s + 2:]
 
     def add(self, text, meta, transaction, link, p1=None, p2=None):
         if meta or text.startswith('\1\n'):
             text = packmeta(meta, text)
         return self.addrevision(text, transaction, link, p1, p2)
 
     def renamed(self, node):
         if self.parents(node)[0] != revlog.nullid:
             return False
         t = self.revision(node)
         m = parsemeta(t)[0]
         if m and "copy" in m:
             return (m["copy"], revlog.bin(m["copyrev"]))
         return False
 
     def size(self, rev):
         """return the size of a given revision"""
 
         # for revisions with renames, we have to go the slow way
         node = self.node(rev)
         if self.renamed(node):
             return len(self.read(node))
         if self._iscensored(rev):
             return 0
 
         # XXX if self.read(node).startswith("\1\n"), this returns (size+4)
         return super(filelog, self).size(rev)
 
     def cmp(self, node, text):
         """compare text with a given file revision
 
         returns True if text is different than what is stored.
         """
 
         t = text
         if text.startswith('\1\n'):
             t = '\1\n\1\n' + text
 
         samehashes = not super(filelog, self).cmp(node, t)
         if samehashes:
             return False
 
         # censored files compare against the empty file
         if self._iscensored(self.rev(node)):
             return text != ''
 
         # renaming a file produces a different hash, even if the data
         # remains unchanged. Check if it's the case (slow):
         if self.renamed(node):
             t2 = self.read(node)
             return t2 != text
 
         return True
 
     def checkhash(self, text, p1, p2, node, rev=None):
         try:
             super(filelog, self).checkhash(text, p1, p2, node, rev=rev)
         except error.RevlogError:
             if _censoredtext(text):
                 raise error.CensoredNodeError(self.indexfile, node)
             raise
 
     def _iscensored(self, rev):
         """Check if a file revision is censored."""
         return self.flags(rev) & revlog.REVIDX_ISCENSORED