# HG changeset patch
# User Martin von Zweigbergk <martinvonz@google.com>
# Date 2018-07-24 05:51:53
# Node ID 0e58c5b207454bfcf7d9ce4df8a30d040708c138
# Parent  6bfd1054d867905ac05ffe7c0ebe97009ae32ab9

mergetool: warn if ui.merge points to nonexistent tool

This adds a warning when ui.merge is configured but points to an
executable that doesn't exist. It gets printed once per fail, but that
seems to be how our other warnings about merge tools are reported.

Differential Revision: https://phab.mercurial-scm.org/D3975

diff --git a/mercurial/filemerge.py b/mercurial/filemerge.py
--- a/mercurial/filemerge.py
+++ b/mercurial/filemerge.py
@@ -208,9 +208,10 @@ def _picktool(repo, ui, path, binary, sy
     if uimerge:
         # external tools defined in uimerge won't be able to handle
         # change/delete conflicts
-        if uimerge not in names and not changedelete:
-            return (uimerge, uimerge)
-        tools.insert(0, (None, uimerge)) # highest priority
+        if check(uimerge, path, symlink, binary, changedelete):
+            if uimerge not in names and not changedelete:
+                return (uimerge, uimerge)
+            tools.insert(0, (None, uimerge)) # highest priority
     tools.append((None, "hgmerge")) # the old default, if found
     for p, t in tools:
         if check(t, None, symlink, binary, changedelete):
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
@@ -1748,7 +1748,9 @@ missingbinary is a merge-tool that doesn
   missingbinary.executable=doesnotexist
   # hg update -C 1
   $ hg merge -y -r 2 --config ui.merge=missingbinary
+  couldn't find merge tool missingbinary (for pattern f)
   merging f
+  couldn't find merge tool missingbinary (for pattern f)
   revision 1
   space
   revision 0