templater: do not strip non-quote characters from template config

Before this patch, the first and last characters were stripped from
ui.logtemplate and template.* if they were the same. It could lead to a
strange result as quotes are optional. See the test for example.

mercurial/templater.py

@@ -868,7 +868,7 b' def _flatten(thing):'
 
 def unquotestring(s):
     '''unwrap quotes if any; otherwise returns unmodified string'''
-    if len(s) < 2 or s[0] != s[-1]:
+    if len(s) < 2 or s[0] not in "'\"" or s[0] != s[-1]:
         return s
     return s[1:-1]
 

tests/test-command-template.t

@@ -71,6 +71,8 b' Quoting for ui.logtemplate'
   8
   $ hg tip --config 'ui.logtemplate="{rev}\n"'
   8
+  $ hg tip --config 'ui.logtemplate=n{rev}\n'
+  n8
 
 Make sure user/global hgrc does not affect tests