modify tmux and ssh to recover SSH_AUTH_SOCK after tmux reconnect

base/.ssh/rc

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# Fix SSH auth socket location so agent forwarding works with tmux.
+if test "$SSH_AUTH_SOCK" ; then
+  ln -sf $SSH_AUTH_SOCK ~/.ssh/ssh_auth_sock
+fi
+

base/.tmux.conf

@@ -21,3 +21,7 @@ if-shell -b '[ "$(echo "$TMUX_VERSION >= 3.3" | bc)" = 1 ]' {
 set-option -a terminal-features 'xterm-256color:RGB'
 set-option -sg escape-time 10
 set-option -g focus-events on
+
+# fix ssh agent when tmux is detached
+set -g update-environment -r
+set-environment -g 'SSH_AUTH_SOCK' ~/.ssh/ssh_auth_sock