sshserver: redirect stdin/stdout early and use duplicated streams

This is what we achieved with hook.redirect(True) plus ui.fout = ui.ferr.

The hook.redirect() function can't be completely removed yet since hgweb
still depends on it. I'm not sure if it is necessary for WSGI servers. CGI
needs it, but does WSGI communicate over stdin/stdout channels?

mercurial/wireprotoserver.py

@@ -18,7 +18,6 b' from .thirdparty import ('
 from . import (
     encoding,
     error,
-    hook,
     pycompat,
     util,
     wireprototypes,
@@ -785,8 +784,7 b' class sshserver(object):'
     def __init__(self, ui, repo, logfh=None):
         self._ui = ui
         self._repo = repo
-        self._fin = ui.fin
-        self._fout = ui.fout
+        self._fin, self._fout = procutil.protectstdio(ui.fin, ui.fout)
 
         # Log write I/O to stdout and stderr if configured.
         if logfh:
@@ -795,11 +793,10 b' class sshserver(object):'
             ui.ferr = util.makeloggingfileobject(
                 logfh, ui.ferr, 'e', logdata=True)
 
-        hook.redirect(True)
-        ui.fout = repo.ui.fout = ui.ferr
-
     def serve_forever(self):
         self.serveuntil(threading.Event())
+        procutil.restorestdio(self._ui.fin, self._ui.fout,
+                              self._fin, self._fout)
         sys.exit(0)
 
     def serveuntil(self, ev):