basefilectx: move __nonzero__ from filectx

mercurial/context.py

@@ -447,6 +447,14 b' class basefilectx(object):'
     def _repopath(self):
         return self._path
 
+    def __nonzero__(self):
+        try:
+            self._filenode
+            return True
+        except error.LookupError:
+            # file is missing
+            return False
+
 class filectx(basefilectx):
     """A filecontext object makes access to data related to a particular
        filerevision convenient."""
@@ -496,14 +504,6 b' class filectx(basefilectx):'
             # considered when solving linkrev issue are on the table.
             return changectx(self._repo.unfiltered(), self._changeid)
 
-    def __nonzero__(self):
-        try:
-            self._filenode
-            return True
-        except error.LookupError:
-            # file is missing
-            return False
-
     def __str__(self):
         return "%s@%s" % (self.path(), short(self.node()))