Fix line param parsing

lines is a positive integer or -1 to disable line limiting. The
default value is 10 if no argument is given.

Fixes #604

src/routes/tasks.js

@@ -59,13 +59,13 @@ function list(req, res, next) {
 function getLogs(req, res, next) {
     assert.strictEqual(typeof req.params.taskId, 'string');
 
-    var lines = req.query.lines ? parseInt(req.query.lines, 10) : 100;
+    var lines = 'lines' in req.query ? parseInt(req.query.lines, 10) : 10; // we ignore last-event-id
     if (isNaN(lines)) return next(new HttpError(400, 'lines must be a number'));
 
     var options = {
         lines: lines,
         follow: false,
-        format: req.query.format
+        format: req.query.format || 'json'
     };
 
     tasks.getLogs(req.params.taskId, options, function (error, logStream) {
@@ -86,7 +86,7 @@ function getLogs(req, res, next) {
 function getLogStream(req, res, next) {
     assert.strictEqual(typeof req.params.taskId, 'string');
 
-    var lines = req.query.lines ? parseInt(req.query.lines, 10) : -10; // we ignore last-event-id
+    var lines = 'lines' in req.query ? parseInt(req.query.lines, 10) : 10; // we ignore last-event-id
     if (isNaN(lines)) return next(new HttpError(400, 'lines must be a valid number'));
 
     function sse(id, data) { return 'id: ' + id + '\ndata: ' + data + '\n\n'; }
@@ -95,7 +95,8 @@ function getLogStream(req, res, next) {
 
     var options = {
         lines: lines,
-        follow: true
+        follow: true,
+        format: 'json'
     };
 
     tasks.getLogs(req.params.taskId, options, function (error, logStream) {