add tmux plugin: tmux-sidebar

A sidebar with the directory tree for the current path. Tries to make tmux more IDE like.

.tmux/scripts/tree_helpers.sh

@@ -0,0 +1,42 @@
+# file sourced from ./sidebar.tmux
+custom_tree_command="$CURRENT_DIR/scripts/custom_tree.sh"
+
+command_exists() {
+	local command="$1"
+	type "$command" >/dev/null 2>&1
+}
+
+tree_command() {
+	local user_command="$(tree_user_command)"
+	if [ -n "$user_command" ]; then
+		echo "$user_command"
+	elif command_exists "tree"; then
+		echo "$TREE_COMMAND"
+	else
+		echo "$custom_tree_command"
+	fi
+}
+
+tree_user_command() {
+	get_tmux_option "$TREE_COMMAND_OPTION" ""
+}
+
+tree_key() {
+	get_tmux_option "$TREE_OPTION" "$TREE_KEY"
+}
+
+tree_focus_key() {
+	get_tmux_option "$TREE_FOCUS_OPTION" "$TREE_FOCUS_KEY"
+}
+
+tree_pager() {
+	get_tmux_option "$TREE_PAGER_OPTION" "$TREE_PAGER"
+}
+
+tree_position() {
+	get_tmux_option "$TREE_POSITION_OPTION" "$TREE_POSITION"
+}
+
+tree_width() {
+	get_tmux_option "$TREE_WIDTH_OPTION" "$TREE_WIDTH"
+}