Merge branch 'master-recursiveTree' into 'master'

Issue #4270: Recursive option for files through API

## What does this MR do?
- Adds recursive param to tree API request. With this param we can get all repository paths in a single request. 
- Related [old github pull request](https://github.com/gitlabhq/gitlabhq/pull/9311)

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

## Why was this MR needed?
Requested in #4270 
## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [X] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [X] API support added
- Tests
  - [X] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Requested in #4270

See merge request !6088

2 files changed, 22 insertions, 4 deletions

diff --git a/app/models/repository.rb b/app/models/repository.rb
index 063dc74021d..4282197faa5 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -631,7 +631,7 @@ class Repository
     @head_tree ||= Tree.new(self, head_commit.sha, nil)
   end
 
-  def tree(sha = :head, path = nil)
+  def tree(sha = :head, path = nil, recursive: false)
     if sha == :head
       if path.nil?
         return head_tree
@@ -640,7 +640,7 @@ class Repository
       end
     end
 
-    Tree.new(self, sha, path)
+    Tree.new(self, sha, path, recursive: recursive)
   end
 
   def blob_at_branch(branch_name, path)
diff --git a/app/models/tree.rb b/app/models/tree.rb
index 7c4ed6e393b..2d1d68dbd81 100644
--- a/app/models/tree.rb
+++ b/app/models/tree.rb
@@ -3,15 +3,16 @@ class Tree
 
   attr_accessor :repository, :sha, :path, :entries
 
-  def initialize(repository, sha, path = '/')
+  def initialize(repository, sha, path = '/', recursive: false)
     path = '/' if path.blank?
 
     @repository = repository
     @sha = sha
     @path = path
+    @recursive = recursive
 
     git_repo = @repository.raw_repository
-    @entries = Gitlab::Git::Tree.where(git_repo, @sha, @path)
+    @entries = get_entries(git_repo, @sha, @path, recursive: @recursive)
   end
 
   def readme
@@ -58,4 +59,21 @@ class Tree
   def sorted_entries
     trees + blobs + submodules
   end
+
+  private
+
+  def get_entries(git_repo, sha, path, recursive: false)
+    current_path_entries = Gitlab::Git::Tree.where(git_repo, sha, path)
+    ordered_entries = []
+
+    current_path_entries.each do |entry|
+      ordered_entries << entry
+
+      if recursive && entry.dir?
+        ordered_entries.concat(get_entries(git_repo, sha, entry.path, recursive: true))
+      end
+    end
+
+    ordered_entries
+  end
 end