[PATCH 2 of 8] test: also deactivate `ui.merge` when testing merge tool

[Boris Feld]

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1541009552 -3600
#      Wed Oct 31 19:12:32 2018 +0100
# Node ID 1f02b29ed5c6637cfa8e844f1b7019f3d90af107
# Parent  d01a6df50fa2c5432f2040afe686e05062e02cce
# EXP-Topic run-tests
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 1f02b29ed5c6
test: also deactivate `ui.merge` when testing merge tool

We are about to introduce a default config for `ui.merge`. Since
`test-merge-tools.t` is about testing merge configuration, we need to make sure
it won't interfere.

diff --git a/tests/test-merge-tools.t b/tests/test-merge-tools.t
--- a/tests/test-merge-tools.t
+++ b/tests/test-merge-tools.t
@@ -1,6 +1,10 @@
 test merge-tools configuration - mostly exercising filemerge.py
 
   $ unset HGMERGE # make sure HGMERGE doesn't interfere with the test
+  $ cat >> $HGRCPATH << EOF
+  > [ui]
+  > merge=
+  > EOF
   $ hg init repo
   $ cd repo