flagprocessors: return sidedata map in `_processflagsread`

Right now, flag processors does not return sidedata, by they will. So, we
prepare the caller to receive it.

Differential Revision: https://phab.mercurial-scm.org/D6811

hgext/remotefilelog/remotefilelog.py

@@ -324,7 +324,7 b' class remotefilelog(flagutil.flagprocess'
         flags = store.getmeta(self.filename, node).get(constants.METAKEYFLAG, 0)
         if flags == 0:
             return rawtext
-        text, verifyhash = self._processflagsread(rawtext, flags)
+        text, verifyhash, sidedata = self._processflagsread(rawtext, flags)
         return text
 
     def rawdata(self, node):

mercurial/revlog.py

@@ -1663,7 +1663,8 b' class revlog(flagutil.flagprocessorsmixi'
             validatehash = self._processflagsraw(rawtext, flags)
             text = rawtext
         else:
-            text, validatehash = self._processflagsread(rawtext, flags)
+            r = self._processflagsread(rawtext, flags)
+            text, validatehash, sidedata = r
         if validatehash:
             self.checkhash(text, node, rev=rev)
         if not validated:

mercurial/revlogutils/flagutil.py

@@ -118,7 +118,8 b' class flagprocessorsmixin(object):'
         processed text and ``validatehash`` is a bool indicating whether the
         returned text should be checked for hash integrity.
         """
-        return self._processflagsfunc(text, flags, 'read')
+        text, vhash = self._processflagsfunc(text, flags, 'read')
+        return text, vhash, {}
 
     def _processflagswrite(self, text, flags):
         """Inspect revision data flags and applies write transformations defined

tests/simplestorerepo.py

@@ -294,7 +294,8 b' class filestorage(flagutil.flagprocessor'
             validatehash = self._processflagsraw(rawtext, flags)
             text = rawtext
         else:
-            text, validatehash = self._processflagsread(rawtext, flags)
+            r = self._processflagsread(rawtext, flags)
+            text, validatehash, sidedata = r
         if validatehash:
             self.checkhash(text, node, rev=rev)