debugextension: change "testedwith" to a list (BC)

It wasn't a list since the formatter couldn't process a list. We have no
such problem now and the -T option is experimental, so we can change it.

mercurial/commands.py

@@ -2423,7 +2423,8 b' def debugextensions(ui, **opts):'
                  _('  location: %s\n'), extsource or "")
 
         fm.condwrite(ui.verbose and exttestedwith, 'testedwith',
-                 _('  tested with: %s\n'), ' '.join(exttestedwith))
+                     _('  tested with: %s\n'),
+                     fm.formatlist(exttestedwith, name='ver'))
 
         fm.condwrite(ui.verbose and extbuglink, 'buglink',
                  _('  bug reporting: %s\n'), extbuglink or "")

tests/test-debugextensions.t

@@ -48,36 +48,39 b''
     "buglink": "",
     "name": "color",
     "source": "*/hgext/color.py*", (glob)
-    "testedwith": "internal"
+    "testedwith": ["internal"]
    },
    {
     "buglink": "",
     "name": "ext1",
     "source": "*/extwithoutinfos.py*", (glob)
-    "testedwith": ""
+    "testedwith": []
    },
    {
     "buglink": "",
     "name": "histedit",
     "source": "*/hgext/histedit.py*", (glob)
-    "testedwith": "internal"
+    "testedwith": ["internal"]
    },
    {
     "buglink": "",
     "name": "mq",
     "source": "*/hgext/mq.py*", (glob)
-    "testedwith": "internal"
+    "testedwith": ["internal"]
    },
    {
     "buglink": "",
     "name": "patchbomb",
     "source": "*/hgext/patchbomb.py*", (glob)
-    "testedwith": "internal"
+    "testedwith": ["internal"]
    },
    {
     "buglink": "",
     "name": "rebase",
     "source": "*/hgext/rebase.py*", (glob)
-    "testedwith": "internal"
+    "testedwith": ["internal"]
    }
   ]
+
+  $ hg debugextensions -T '{ifcontains("internal", testedwith, "", "{name}\n")}'
+  ext1