added support for custom variables defined in ~/.tmux.conf.local

closes #96, closes #394

.tmux.conf.local

@@ -1,3 +1,4 @@
+# : << EOF
 # https://github.com/gpakosz/.tmux
 # (‑●‑●)> dual licensed under the WTFPL v2 license and the MIT license,
 #         without any warranty.
@@ -293,3 +294,28 @@ tmux_conf_copy_to_os_clipboard=false
 
 # move status line to top
 #set -g status-position top
+
+
+# -- custom variables ----------------------------------------------------------
+# to define a custom #{foo} variable, define a POSIX shell function between the
+# '# EOF' and the '# "$@"' lines. Please note that the opening brace { character
+# must be on the same line as the function name otherwise the parse won't detect
+# it.
+#
+# then, use #{foo} in e.g. the 'tmux_conf_theme_status_left' or the
+# 'tmux_conf_theme_status_right' variables.
+
+# # /!\ do not remove the following line
+# EOF
+#
+# weather() {
+#   curl -m 1 wttr.in?format=3 2>/dev/null
+#   sleep 900 # sleep for 15 minutes, throttle network requests whatever the value of status-interval
+# }
+#
+# online() {
+#   ping -t 1 -c 1 1.1.1.1 >/dev/null 2>&1 && printf '✔' || printf '✘'
+# }
+#
+# "$@"
+# # /!\ do not remove the previous line