ui: suggest config --edit when no username is set

mercurial/ui.py

@@ -449,7 +449,9 b' class ui(object):'
             except KeyError:
                 pass
         if not user:
-            raise util.Abort(_('no username supplied (see "hg help config")'))
+            raise util.Abort(_('no username supplied'),
+                             hint=_('use "hg config --edit" '
+                                    ' to set your username'))
         if "\n" in user:
             raise util.Abort(_("username %s contains a newline\n") % repr(user))
         return user

tests/test-install.t

@@ -16,7 +16,7 b' hg debuginstall with no username'
   checking templates (*mercurial?templates)... (glob)
   checking commit editor...
   checking username...
-   no username supplied (see "hg help config")
+   no username supplied
    (specify a username in your configuration file)
   1 problems detected, please check your install!
   [1]