cmdutil: copy auth section in remoteui

This allows me to specify an auth section in a .hg/hgrc instead of just
a global or user-level hgrc.

mercurial/cmdutil.py

@@ -111,11 +111,16 b' def remoteui(src, opts):'
         v = opts.get(o) or src.config('ui', o)
         if v:
             dst.setconfig("ui", o, v)
+
     # copy bundle-specific options
     r = src.config('bundle', 'mainreporoot')
     if r:
         dst.setconfig('bundle', 'mainreporoot', r)
 
+    # copy auth section settings
+    for key, val in src.configitems('auth'):
+        dst.setconfig('auth', key, val)
+
     return dst
 
 def revpair(repo, revs):