Enable vi-mode yank on macOS

tmux.conf

@@ -71,7 +71,8 @@ bind-key C-u copy-mode -u
 # Begin selection in copy mode with v not Space
 bind-key -T copy-mode-vi v send-keys -X begin-selection
 # Yank to the system clipboard in copy mode
-if -b '[ "`uname`" = "Linux" ]' \
+if -b '[ "`uname`" = "Darwin" ]' \
+  "bind-key -T copy-mode-vi y send-keys -X copy-pipe-and-cancel 'reattach-to-user-namespace pbcopy'" \
   "bind-key -T copy-mode-vi y send-keys -X copy-pipe-and-cancel 'xsel -i -p && xsel -o -p | xsel -i -b'"
 
 # Left status style