[PATCH 4 of 6 v2] patch: add hgpatch to data for # HG changset patches

[timeless]

# HG changeset patch
# User timeless <timeless at mozdev.org>
# Date 1451521664 0
#      Thu Dec 31 00:27:44 2015 +0000
# Node ID f157383b6e9967a6c4a43ee30679f4eba6a1d6c5
# Parent  0179b3fbf17aa787dce200d03d2deb924246fda5
patch: add hgpatch to data for # HG changset patches

diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -249,6 +249,7 @@
                 for line in payload[:m.start(0)].splitlines():
                     if line.startswith('# HG changeset patch') and not hgpatch:
                         ui.debug('patch generated by hg export\n')
+                        data['hgpatch'] = 'True'
                         hgpatch = True
                         hgpatchheader = True
                         # drop earlier commit message content