[PATCH 5 of 6 V2] py3: add a test to show `hg diff` works on Python 3

[Pulkit Goyal]

# HG changeset patch
# User Pulkit Goyal <7895pulkit at gmail.com>
# Date 1496378640 -19800
#      Fri Jun 02 10:14:00 2017 +0530
# Node ID f6a8bfcf09665b66f0698c0a0f40d48212da9458
# Parent  d6d7a160ee30b4296c2750cbf341cc550fe1657f
py3: add a test to show `hg diff` works on Python 3

diff --git a/tests/test-py3-commands.t b/tests/test-py3-commands.t
--- a/tests/test-py3-commands.t
+++ b/tests/test-py3-commands.t
@@ -118,6 +118,13 @@
   $ $PYTHON3 $HGBIN add iota
   $ $PYTHON3 $HGBIN status
   A iota
+  $ hg diff --nodates --git
+  diff --git a/iota b/iota
+  new file mode 100644
+  --- /dev/null
+  +++ b/iota
+  @@ -0,0 +1,1 @@
+  +This is the file 'iota'.
   $ $PYTHON3 $HGBIN commit --message 'commit performed in Python 3'
   $ $PYTHON3 $HGBIN status