Test case for the misleading message on bad permissions.

tests/test-ro-message

@@ -0,0 +1,17 b''
+#!/bin/sh
+HG=hg
+"$HG" init
+mkdir b
+echo 'Bouncy' >b/bouncy
+echo 'tricycle' >b/vehicle
+"$HG" add b/bouncy
+"$HG" add b/vehicle
+"$HG" commit -m 'Adding bouncy'
+echo 'bouncy' >>b/bouncy
+"$HG" commit -m 'Making it bouncier'
+"$HG" update -C 0
+echo 'stationary' >>b/vehicle
+"$HG" commit -m 'Clarifying the vehicle.'
+"$HG" update -C 1
+chmod a-w b/vehicle
+"$HG" update -m 2 2>&1 | sed 's|^\(.*[ 	]\)/tmp/[^/]*/\(.*\)$|\1\2|g'

tests/test-ro-message.out

@@ -0,0 +1,1 b''
+abort: Permission denied - test-ro-message/b/vehicle