Add logFile option to startTask

src/tasks.js

@@ -98,16 +98,19 @@ function update(id, task, callback) {
     });
 }
 
-function startTask(type, args) {
+function startTask(type, args, options) {
     assert.strictEqual(typeof type, 'string');
     assert(Array.isArray(args));
+    assert(!options || typeof options === 'object');
 
     let events = new EventEmitter();
 
+    options = options || {};
+
     taskdb.add({ type: type, percent: 0, message: 'Starting', args: args }, function (error, taskId) {
         if (error) return events.emit('error', new TaskError(TaskError.INTERNAL_ERROR, error));
 
-        const logFile = `${paths.TASKS_LOG_DIR}/${taskId}.log`;
+        const logFile = options.logFile || `${paths.TASKS_LOG_DIR}/${taskId}.log`;
         let fd = safe.fs.openSync(logFile, 'w'); // will autoclose
         if (!fd) {
             debug(`startTask: unable to get log filedescriptor ${safe.error.message}`);