Merge branch 'fix-submodules-with-relative-links' into 'master'

Fix broken file browsing with a submodule that has a relative link

## What does this MR do?

This MR fixes an error that occurs when browsing a submodule with a relative link.

### Are there points in the code the reviewer needs to double check?

I re-wrote the function because I was confused by how the first one was supposed to work. Please review if it's clearer.

### Why was this MR needed?

A 500 Error would occur when using the file browser on a repo with a submodule. Here's how to reproduce the bug:

1. Start a new project in GitLab.
2. Clone git://git.gniibe.org/gnuk/gnuk.git/ locally.
3. Push repo to new project.
4. Click on "Files" in the project.

The .gitmodules file:
```
[submodule "chopstx"]
        path = chopstx
        url = ../../chopstx/chopstx.git
```
### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

1. #775
2. #1385
3. https://github.com/gitlabhq/gitlabhq/issues/8153
4. https://github.com/gitlabhq/gitlabhq/issues/8881
5. https://github.com/gitlabhq/gitlabhq/issues/7554

See merge request !508

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.10.0 (unreleased)
+  - Fix broken file browsing with a submodule that contains a relative link (Stan Hu)
   - Fix bug where Wiki pages that included a '/' were no longer accessible (Stan Hu)
   - Fix bug where error messages from Dropzone would not be displayed on the issues page (Stan Hu)
   - Add ability to configure Reply-To address in gitlab.yml (Stan Hu)

app/helpers/submodule_helper.rb

@@ -53,15 +53,22 @@ module SubmoduleHelper
   end
 
   def relative_self_links(url, commit)
-    if url.scan(/(\.\.\/)/).size == 2
-      base = url[/([^\/]*\/[^\/]*)\.git/, 1]
-    else
-      base = [ @project.group.path, '/', url[/([^\/]*)\.git/, 1] ].join('')
+    # Map relative links to a namespace and project
+    # For example:
+    # ../bar.git -> same namespace, repo bar
+    # ../foo/bar.git -> namespace foo, repo bar
+    # ../../foo/bar/baz.git -> namespace bar, repo baz
+    components = url.split('/')
+    base = components.pop.gsub(/.git$/, '')
+    namespace = components.pop.gsub(/^\.\.$/, '')
+
+    if namespace.empty?
+      namespace = @project.group.path
     end
 
     [
-      namespace_project_path(base.namespace, base),
-      namespace_project_tree_path(base.namespace, base, commit)
+      namespace_project_path(namespace, base),
+      namespace_project_tree_path(namespace, base, commit)
     ]
   end
 end

spec/helpers/submodule_helper_spec.rb

 require 'spec_helper'
 
 describe SubmoduleHelper do
+  include RepoHelpers
+
   describe 'submodule links' do
     let(:submodule_item) { double(id: 'hash', path: 'rack') }
     let(:config) { Gitlab.config.gitlab }
@@ -111,6 +113,39 @@ describe SubmoduleHelper do
         expect(submodule_links(submodule_item)).to eq([ repo.submodule_url_for, nil ])
       end
     end
+
+    context 'submodules with relative links' do
+      let(:group) { create(:group) }
+      let(:project) { create(:project, group: group) }
+
+      before do
+        self.instance_variable_set(:@project, project)
+      end
+
+      it 'one level down' do
+        commit_id = sample_commit[:id]
+        result = relative_self_links('../test.git', commit_id)
+        expect(result).to eq(["/#{group.path}/test", "/#{group.path}/test/tree/#{commit_id}"])
+      end
+
+      it 'two levels down' do
+        commit_id = sample_commit[:id]
+        result = relative_self_links('../../test.git', commit_id)
+        expect(result).to eq(["/#{group.path}/test", "/#{group.path}/test/tree/#{commit_id}"])
+      end
+
+      it 'one level down with namespace and repo' do
+        commit_id = sample_commit[:id]
+        result = relative_self_links('../foobar/test.git', commit_id)
+        expect(result).to eq(["/foobar/test", "/foobar/test/tree/#{commit_id}"])
+      end
+
+      it 'two levels down with namespace and repo' do
+        commit_id = sample_commit[:id]
+        result = relative_self_links('../foobar/baz/test.git', commit_id)
+        expect(result).to eq(["/baz/test", "/baz/test/tree/#{commit_id}"])
+      end
+    end
   end
 
   def stub_url(url)