[tmux] make some commands version agnostic.

.tmux.conf

@@ -20,13 +20,16 @@ bind-key -r l select-pane -R
 set-window-option -g mode-keys vi
 # start selection with v and end with y
 ## tmux <= 2.3
-bind-key -t vi-copy 'v' begin-selection
+if-shell 'tmux -V | grep -Eq "tmux 2\.[0-3]"' " \
-bind-key -t vi-copy 'y' copy-selection
+    bind-key -t vi-copy 'v' begin-selection; \
-## tmux > 2.3
+    bind-key -t vi-copy 'y' copy-selection; \
-# bind-key -T copy-mode-vi v send-keys -X begin-selection
+    bind -t vi-copy y copy-pipe 'xclip -sel clip -i'; \
-# bind-key -T copy-mode-vi y send-keys -X copy-selection
+"
-# use system clipboard
+
-bind -t vi-copy y copy-pipe "xclip -sel clip -i"
+if-shell 'tmux -V | grep -Eq "tmux 2\.[4-9]"' " \
+    bind-key -T copy-mode-vi v send-keys -X begin-selection; \
+    bind-key -T copy-mode-vi y send-keys -X copy-selection; \
+"
 # bind-key -T copy-mode-vi y send-keys -X copy-pipe-and-cancel 'xclip -sel clip -i'
 
 # Faster repeat time