diff -r 0664be4f0c1f -r ad1c07008e0b mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Sat Apr 14 09:57:44 2018 -0700
+++ b/mercurial/debugcommands.py	Sat Apr 14 11:49:57 2018 -0700
@@ -2626,6 +2626,8 @@
         ('', 'localssh', False, _('start an SSH server for this repo')),
         ('', 'peer', '', _('construct a specific version of the peer')),
         ('', 'noreadstderr', False, _('do not read from stderr of the remote')),
+        ('', 'nologhandshake', False,
+         _('do not log I/O related to the peer handshake')),
     ] + cmdutil.remoteopts,
     _('[PATH]'),
     optionalrepo=True)
@@ -2921,8 +2923,14 @@
             # the peer instance to be useful.
             with ui.configoverride({
                 ('experimental', 'httppeer.advertise-v2'): True}):
+                if opts['nologhandshake']:
+                    ui.pushbuffer()
+
                 peer = httppeer.makepeer(ui, path, opener=opener)
 
+                if opts['nologhandshake']:
+                    ui.popbuffer()
+
             if not isinstance(peer, httppeer.httpv2peer):
                 raise error.Abort(_('could not instantiate HTTP peer for '
                                     'wire protocol version 2'),