filemerge: make warning message more i18n friendly

Before this patch, " specified for " part of warning messages
(e.g. "couldn't find merge tool TOOL specified for PAT") isn't
translatable.

mercurial/filemerge.py

@@ -133,7 +133,7 b' def _picktool(repo, ui, path, binary, sy'
     def check(tool, pat, symlink, binary, changedelete):
         tmsg = tool
         if pat:
-            tmsg += " specified for " + pat
+            tmsg = _("%s (for pattern %s)") % (tool, pat)
         if not _findtool(ui, tool):
             if pat: # explicitly requested tool deserves a warning
                 ui.warn(_("couldn't find merge tool %s\n") % tmsg)

tests/test-merge-tools.t

@@ -392,9 +392,9 b' merge-patterns specifies executable not '
   true.executable=cat
   # hg update -C 1
   $ hg merge -r 2 --config merge-patterns.f=true --config merge-tools.true.executable=nonexistentmergetool
-  couldn't find merge tool true specified for f
+  couldn't find merge tool true (for pattern f)
   merging f
-  couldn't find merge tool true specified for f
+  couldn't find merge tool true (for pattern f)
   merging f failed!
   0 files updated, 0 files merged, 0 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon
@@ -418,9 +418,9 b' merge-patterns specifies executable with'
   true.executable=cat
   # hg update -C 1
   $ hg merge -r 2 --config merge-patterns.f=true --config merge-tools.true.executable=/nonexistent/mergetool
-  couldn't find merge tool true specified for f
+  couldn't find merge tool true (for pattern f)
   merging f
-  couldn't find merge tool true specified for f
+  couldn't find merge tool true (for pattern f)
   merging f failed!
   0 files updated, 0 files merged, 0 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges or 'hg update -C .' to abandon