revlog: drop the df argument to `revision`

The intend of this argument is better filled by the `revlog.reading` or
`revlog._writing` context. So we drop it to leave rooms for further cleanup and
improvements.

mercurial/filelog.py

@@ -107,8 +107,8 b' class filelog:'
     def iscensored(self, rev):
         return self._revlog.iscensored(rev)
 
-    def revision(self, node, _df=None):
-        return self._revlog.revision(node, _df=_df)
+    def revision(self, node):
+        return self._revlog.revision(node)
 
     def rawdata(self, node, _df=None):
         return self._revlog.rawdata(node, _df=_df)

mercurial/interfaces/repository.py

@@ -1282,7 +1282,7 b' class imanifeststorage(interfaceutil.Int'
     def linkrev(rev):
         """Obtain the changeset revision number a revision is linked to."""
 
-    def revision(node, _df=None):
+    def revision(node):
         """Obtain fulltext data for a node."""
 
     def rawdata(node, _df=None):

mercurial/manifest.py

@@ -1821,8 +1821,8 b' class manifestrevlog:'
     def checksize(self):
         return self._revlog.checksize()
 
-    def revision(self, node, _df=None):
-        return self._revlog.revision(node, _df=_df)
+    def revision(self, node):
+        return self._revlog.revision(node)
 
     def rawdata(self, node, _df=None):
         return self._revlog.rawdata(node, _df=_df)

mercurial/revlog.py

@@ -1954,13 +1954,11 b' class revlog:'
 
         return mdiff.textdiff(self.rawdata(rev1), self.rawdata(rev2))
 
-    def revision(self, nodeorrev, _df=None):
+    def revision(self, nodeorrev):
         """return an uncompressed revision of a given node or revision
         number.
-
-        _df - an existing file handle to read from. (internal-only)
         """
-        return self._revisiondata(nodeorrev, _df)
+        return self._revisiondata(nodeorrev)
 
     def sidedata(self, nodeorrev, _df=None):
         """a map of extra data related to the changeset but not part of the hash