Implement validation support in Etcher CLI (#361)

Signed-off-by: Juan Cruz Viotti <jviottidc@gmail.com>

lib/cli/cli.js

@@ -41,6 +41,7 @@ module.exports = yargs
 
   // Examples
   .example('$0 raspberry-pi.img')
+  .example('$0 --no-check raspberry-pi.img')
   .example('$0 -d /dev/disk2 ubuntu.iso')
   .example('$0 -d /dev/disk2 -y rpi.img')
 
@@ -87,6 +88,12 @@ module.exports = yargs
       string: true,
       alias: 'd'
     },
+    check: {
+      describe: 'validate write',
+      boolean: true,
+      alias: 'c',
+      default: true
+    },
     robot: {
       describe: 'parse-able output without interactivity',
       boolean: true,

lib/cli/etcher.js

@@ -49,13 +49,16 @@ form.run([
     throw new Error('Aborted');
   }
 
-  const progressBar = new visuals.Progress('Burning');
+  const progressBars = {
+    write: new visuals.Progress('Flashing'),
+    check: new visuals.Progress('Validating')
+  };
 
   return writer.writeImage(options._[0], {
     device: answers.drive
   }, {
     unmountOnSuccess: false,
-    validateWriteOnSuccess: false
+    validateWriteOnSuccess: options.check
   }, function(state) {
 
     if (options.robot) {
@@ -66,16 +69,20 @@ form.run([
         Math.floor(state.speed)
       ].join(' '));
     } else {
-      progressBar.update(state);
+      progressBars[state.type].update(state);
     }
 
   });
-}).then(function() {
+}).then(function(success) {
 
   if (options.robot) {
-    console.log('done');
-  } else {
+    return console.log(`done ${success}`);
+  }
+
+  if (success) {
     console.log('Your flash is complete!');
+  } else {
+    console.error('Validation failed!');
   }
 
 }).catch(function(error) {