cmp: document the fact that we return True if content is different

This is similar to the __builtin__.cmp behaviour, but still not
straightforward, as the dailylife meaning of a comparison usually is
"find out if they are different".

mercurial/context.py

@@ -353,6 +353,10 b' class filectx(object):'
         return self._filelog.size(self._filerev)
 
     def cmp(self, text):
+        """compare text with stored file revision
+
+        returns True if text is different than what is stored.
+        """
         return self._filelog.cmp(self._filenode, text)
 
     def renamed(self):
@@ -932,6 +936,10 b' class workingfilectx(filectx):'
             return (t, tz)
 
     def cmp(self, text):
+        """compare text with disk content
+
+        returns True if text is different than what is on disk.
+        """
         return self._repo.wread(self._path) != text
 
 class memctx(object):

mercurial/filelog.py

@@ -56,7 +56,10 b' class filelog(revlog.revlog):'
         return revlog.revlog.size(self, rev)
 
     def cmp(self, node, text):
-        """compare text with a given file revision"""
+        """compare text with a given file revision
+
+        returns True if text is different than what is stored.
+        """
 
         # for renames, we have to go the slow way
         if text.startswith('\1\n') or self.renamed(node):

mercurial/revlog.py

@@ -943,7 +943,10 b' class revlog(object):'
         raise LookupError(id, self.indexfile, _('no match found'))
 
     def cmp(self, node, text):
-        """compare text with a given file revision"""
+        """compare text with a given file revision
+
+        returns True if text is different than what is stored.
+        """
         p1, p2 = self.parents(node)
         return hash(text, p1, p2) != node