From patchwork Thu Oct 26 18:07:19 2017
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Subject: filemerge: pass a default value to _toolstr
From: Kostia Balytskyi <ikostia@fb.com>
X-Patchwork-Id: 25287
Message-Id: <81db944aae69a96175fd.1509041239@devvm1416.lla2.facebook.com>
To: <mercurial-devel@mercurial-scm.org>
Date: Thu, 26 Oct 2017 11:07:19 -0700

# HG changeset patch
# User Kostia Balytskyi <ikostia@fb.com>
# Date 1509041226 25200
#      Thu Oct 26 11:07:06 2017 -0700
# Branch stable
# Node ID 81db944aae69a96175fd0d917834e67534a92735
# Parent  9e9ff559440e4733fda49ddeb1b9ce5e7c9660af
filemerge: pass a default value to _toolstr

After a refactoring, _toolstr stopped having default="" as one of it's args,
therefore when called without a default it returns None and not "". This causes
concatenation to fail.

diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -116,7 +116,7 @@ def findexternaltool(ui, tool):
             continue
         p = util.lookupreg(k, _toolstr(ui, tool, "regname"))
         if p:
-            p = util.findexe(p + _toolstr(ui, tool, "regappend"))
+            p = util.findexe(p + _toolstr(ui, tool, "regappend", ""))
             if p:
                 return p
     exe = _toolstr(ui, tool, "executable", tool)