Add a small dance to daemon() to reattach tmux to the user's namespace (which

allows access to the clipboard) on OS X 10.10 and above.

Chis Johnsen has done much work on and documentation of this issue, the code is
copied (with some tweaks) from his reattach-to-user-namespace at:

    https://github.com/ChrisJohnsen/tmux-MacOSX-pasteboard

Tested by Enrico Ghirardi.

Will see how this goes, if it breaks stuff it might go away again.

compat/daemon-darwin.c

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2017 Nicholas Marriott <nicholas.marriott@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Copyright (c) 2011-2013, Chris Johnsen <chris_johnsen@pobox.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *     1. Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *     2. Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <sys/types.h>
+
+#include <mach/mach.h>
+
+#include <Availability.h>
+#include <unistd.h>
+
+void daemon_darwin(void);
+
+#ifdef __MAC_10_10
+
+extern kern_return_t	bootstrap_look_up_per_user(mach_port_t, const char *,
+			    uid_t, mach_port_t *);
+extern kern_return_t	bootstrap_get_root(mach_port_t, mach_port_t *);
+
+void
+daemon_darwin(void)
+{
+	mach_port_t	root = MACH_PORT_NULL;
+	mach_port_t	s = MACH_PORT_NULL;
+	uid_t		uid;
+
+	uid = getuid();
+	if (bootstrap_get_root(bootstrap_port, &root) == KERN_SUCCESS &&
+	    bootstrap_look_up_per_user(root, NULL, uid, &s) == KERN_SUCCESS &&
+	    task_set_bootstrap_port(mach_task_self(), s) == KERN_SUCCESS &&
+	    mach_port_deallocate(mach_task_self(), bootstrap_port) == KERN_SUCCESS)
+		bootstrap_port = s;
+}
+
+#else
+
+void
+daemon_darwin(void)
+{
+}
+
+#endif

compat/daemon.c

@@ -28,12 +28,18 @@
  * SUCH DAMAGE.
  */
 
+#include <sys/types.h>
+
 #include <fcntl.h>
 #include <unistd.h>
 #include <stdlib.h>
 
 #include "compat.h"
 
+#ifdef __APPLE__
+extern void daemon_darwin(void);
+#endif
+
 int
 daemon(int nochdir, int noclose)
 {
@@ -61,5 +67,9 @@ daemon(int nochdir, int noclose)
 		if (fd > 2)
 			(void)close (fd);
 	}
+
+#ifdef __APPLE__
+	daemon_darwin();
+#endif
 	return (0);
 }