[PATCH 2 of 3 V2] revlog: raise WdirUnsupported when wdirrev is passed

[Pulkit Goyal]

# HG changeset patch
# User Pulkit Goyal <7895pulkit at gmail.com>
# Date 1495201326 -19800
#      Fri May 19 19:12:06 2017 +0530
# Node ID 497d73787ea6e0b0ec8aa2262812c82086dc8e8b
# Parent  2adbd2d46cd7588d75201108f6e02b92d1480022
revlog: raise WdirUnsupported when wdirrev is passed

revlog.parentrevs() is called while evaluating ^ operator in revsets. When wdir
is passed, it raises IndexError. This patch raises WdirUnsupported if wdir is
passed in the function. The error will be caugth in future patches.

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -26,6 +26,7 @@
     hex,
     nullid,
     nullrev,
+    wdirrev,
 )
 from .i18n import _
 from . import (
@@ -477,7 +478,12 @@
         return self.index[rev][4]
 
     def parentrevs(self, rev):
-        return self.index[rev][5:7]
+        try:
+            return self.index[rev][5:7]
+        except IndexError:
+            if rev == wdirrev:
+                raise error.WdirUnsupported("wdir() is not supported")
+            raise
 
     def node(self, rev):
         return self.index[rev][7]