tmux: reload: unset/reset global options that are appended to

This reverts commit 468b52d.

tmux.common.conf

@@ -23,7 +23,6 @@ set-window-option -g xterm-keys on
 
 # Setup defaults from xterm* also for urxvt (minus Ms for set-selection).
 # Asked about this on the mailing list (rejected): https://sourceforge.net/p/tmux/mailman/message/33169870/
-# TODO: should not append when reloading?!
 set -ga terminal-overrides ",rxvt*:XT:Cs=\\E]12;%p1%s\\007:Cr=\\E]112\\007:Ss=\\E[%p1%d q:Se=\\E[2 q"
 
 # Mouse support.
@@ -60,8 +59,11 @@ bind a send-prefix
 # bind C-A send-prefix \; send-prefix
 # bind -n C-^ send-keys C-^
 
-# easy reloading of config
-bind R source-file ~/.tmux.conf \; display "Reloaded!"
+# Reload config: unset/reset options that are appended to.
+# Unsetting global config vars is fixed in Git for tmux 2.1.
+bind R set -gu update-environment \; \
+    set -gu terminal-overrides \; \
+    source-file ~/.tmux.conf \; display "Reloaded!"
 
 bind C-a last-window
 bind -r Tab select-pane -t :.+