ui: enable alias exception when reading config in plain mode

When in plain mode with "alias" present in the exception list,
keep the aliases. This will be used later to enable auto-completion.

Signed-off-by: "Yann E. MORIN" <[e-mail]>

mercurial/ui.py

@@ -82,10 +82,12 b' class ui(object):'
                       'traceback', 'verbose'):
                 if k in cfg['ui']:
                     del cfg['ui'][k]
+            for k, v in cfg.items('defaults'):
+                del cfg['defaults'][k]
+        # Don't remove aliases from the configuration if in the exceptionlist
+        if self.plain('alias'):
             for k, v in cfg.items('alias'):
                 del cfg['alias'][k]
-            for k, v in cfg.items('defaults'):
-                del cfg['defaults'][k]
 
         if trusted:
             self._tcfg.update(cfg)