From: James McCoy <jamessan@debian.org>
Date: Wed, 1 Aug 2018 20:44:36 -0400
Subject: ssh-no-controlmaster

Bug #413102: Avoid accidentally becoming an ssh ControlMaster.
Bug #413102: Avoid accidentally becoming an ssh ControlMaster.

If you set ControlMaster via your ssh config:
.ssh/config:
Host *
    ControlMaster auto
    Controlpath ~/.ssh/master-%r@%h:%p

you can get 'svn: Can't write to connection: Broken pipe' with certain
ssh commands, because svn can open multiple ssh sessions and kill them
at unpredictable times.

I don't really think the problem is either svn's or openssh's fault,
but this is the obvious way to avoid it.  We will still use ssh
connection sharing, but only if a ControlMaster is already present.
---
 subversion/libsvn_ra_svn/client.c    | 2 +-
 subversion/libsvn_subr/config_file.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/subversion/libsvn_ra_svn/client.c b/subversion/libsvn_ra_svn/client.c
index f484519..c6e3d77 100644
--- a/subversion/libsvn_ra_svn/client.c
+++ b/subversion/libsvn_ra_svn/client.c
@@ -399,7 +399,7 @@ static svn_error_t *find_tunnel_agent(const char *tunnel,
        * versions have it too. If the user is using some other ssh
        * implementation that doesn't accept it, they can override it
        * in the [tunnels] section of the config. */
-      val = "$SVN_SSH ssh -q --";
+      val = "$SVN_SSH ssh -q -o ControlMaster=no --";
     }
 
   if (!val || !*val)
diff --git a/subversion/libsvn_subr/config_file.c b/subversion/libsvn_subr/config_file.c
index 9c0a83a..ffb9524 100644
--- a/subversion/libsvn_subr/config_file.c
+++ b/subversion/libsvn_subr/config_file.c
@@ -1447,7 +1447,7 @@ svn_config_ensure(const char *config_dir, apr_pool_t *pool)
         "### passed to the tunnel agent as <user>@<hostname>.)  If the"      NL
         "### built-in ssh scheme were not predefined, it could be defined"   NL
         "### as:"                                                            NL
-        "# ssh = $SVN_SSH ssh -q --"                                         NL
+        "# ssh = $SVN_SSH ssh -q -o ControlMaster=no --"                     NL
         "### If you wanted to define a new 'rsh' scheme, to be used with"    NL
         "### 'svn+rsh:' URLs, you could do so as follows:"                   NL
         "# rsh = rsh --"                                                     NL
