debugssl: allow a URL to be specified without a local repository

This was the original intent, but I bungled the logic.  Otherwise if there is a
certificate chain issue, the repository can't be cloned in order for there to be
a repo object.  I think I missed this case because I was inside of a Mercurial
clone as I was originally developing and testing this.

mercurial/debugcommands.py

@@ -2078,10 +2078,10 b' def debugssl(ui, repo, source=None, **op'
                             'Windows'))
 
     if not source:
-        source = "default"
-    elif not repo:
+        if not repo:
         raise error.Abort(_("there is no Mercurial repository here, and no "
                             "server specified"))
+        source = "default"
 
     source, branches = hg.parseurl(ui.expandpath(source))
     url = util.url(source)