add optional config for postCmd

cli.js

@@ -3,6 +3,8 @@
 
 const argv = require('minimist')(process.argv.slice(2));
 const swm = require('./swm.js');
+const config = require('./config.js');
+const postCmd = argv.postCmd || config.postCmd;
 
 if (argv.help || argv.h) {
     console.log(
@@ -10,7 +12,7 @@ if (argv.help || argv.h) {
 
 Usage:
 
-'swm [monitor-1...montior-n]' e.g. 'swm LVDS1 HDMI1'
+'swm [monitor-1...montior-n] [--postCmd="cmd"]' e.g. 'swm LVDS1 HDMI1'
 
 If 'monitor-1' to 'monitor-n' is specified 'swm' will turn on these monitors
 and place them from left to right in the order given. If a provided monitor is
@@ -19,9 +21,21 @@ not connected it will be skipped.
 If no monitors are specified all connected monitors will be turned on and
 placed from left to right in alphabetical order of their name.
 
+If "--postCmd" is given, this command is executed after switching the monitors.
+This is usefull to tell your window manager to re-detect monitors, e.g. for
+herbstluftwm "herbstclient reload".
+
 'swm -l' or 'swm --list'
 
-List all devices with the connectivity status.`
+List all devices with the connectivity status.
+
+The configuration can be placed in "$XDG_CONFIG_HOME/switchmon/config.json" in
+the form of
+
+{
+    "postCmd": "some command"
+}`
+
     );
 
     process.exit(2);
@@ -40,7 +54,7 @@ if (argv.list || argv.l) {
     swm.getDevices()
         .then(swm.generateXrandrOptions.bind(null, argv._))
         .then(swm.switchDevices)
-        .then(swm.executePostCmd.bind(null, argv.postCmd))
+        .then(swm.executePostCmd.bind(null, postCmd))
         .catch(err => {
             console.error(err);
         });