basefilectx: move p2 from filectx

mercurial/context.py

@@ -553,6 +553,12 b' class basefilectx(object):'
     def p1(self):
         return self.parents()[0]
 
+    def p2(self):
+        p = self.parents()
+        if len(p) == 2:
+            return p[1]
+        return filectx(self._repo, self._path, fileid=-1, filelog=self._filelog)
+
 class filectx(basefilectx):
     """A filecontext object makes access to data related to a particular
        filerevision convenient."""
@@ -638,12 +644,6 b' class filectx(basefilectx):'
                 pass
         return renamed
 
-    def p2(self):
-        p = self.parents()
-        if len(p) == 2:
-            return p[1]
-        return filectx(self._repo, self._path, fileid=-1, filelog=self._filelog)
-
     def children(self):
         # hard for renames
         c = self._filelog.children(self._filenode)