[PATCH 3 of 3] py3: add test to show `hg merge` works

[Yuya Nishihara]

On Sat, 10 Jun 2017 13:51:55 +0530, Pulkit Goyal wrote:
> # HG changeset patch
> # User Pulkit Goyal <7895pulkit at gmail.com>
> # Date 1496862836 -19800
> #      Thu Jun 08 00:43:56 2017 +0530
> # Node ID 5670e6840252c312bd488133e1cdf42729c12696
> # Parent  36150d28b8a1d517c531542476329b47c18f49c2
> py3: add test to show `hg merge` works

> +  $ hg merge

Here 'hg' is py2. You'll need $PYTHON3 $HGBIN.