[fix] don't urlescape path of post asset

fixes hexojs#1562

Changes to be committed:
	modified:   lib/models/post_asset.js
	modified:   test/scripts/tags/asset_img.js

lib/models/post_asset.js

@@ -2,7 +2,6 @@
 
 var Schema = require('warehouse').Schema;
 var pathFn = require('path');
-var url = require('url');
 
 module.exports = function(ctx) {
   var PostAsset = new Schema({
@@ -18,7 +17,9 @@ module.exports = function(ctx) {
     var post = Post.findById(this.post);
     if (!post) return;
 
-    return url.resolve(post.path, this.slug);
+    // PostAsset.path is file path relative to `public_dir`
+    // no need to urlescape, #1562
+    return pathFn.join(post.path, this.slug);
   });
 
   PostAsset.virtual('source').get(function() {

test/scripts/tags/asset_img.js

@@ -25,11 +25,18 @@ describe('asset_img', function() {
     }).then(function(post_) {
       post = post_;
 
-      return PostAsset.insert({
-        _id: 'bar',
-        slug: 'bar',
-        post: post._id
-      });
+      return Promise.all([
+        PostAsset.insert({
+          _id: 'bar',
+          slug: 'bar',
+          post: post._id
+        }),
+        PostAsset.insert({
+          _id: 'file with space',
+          slug: 'file with space',
+          post: post._id
+        })
+      ]);
     });
   });
 
@@ -41,6 +48,12 @@ describe('asset_img', function() {
     assetImg('bar title').should.eql('<img src="/foo/bar" alt="title" title="title">');
   });
 
+  it('with space', function() {
+    // {% asset_img "file with space" "title with space" %}
+    assetImgTag.call(post, ['file with space', 'title with space'])
+      .should.eql('<img src="/foo/file with space" alt="title with space" title="title with space">');
+  });
+
   it('no slug', function() {
     should.not.exist(assetImg(''));
   });