Add repo compare API

lib/gitlab/client/repositories.rb

@@ -74,5 +74,20 @@ def commit_diff(project, sha)
       get("/projects/#{project}/repository/commits/#{sha}/diff") 
     end
     alias_method :repo_commit_diff, :commit_diff
+
+    # Compare branches, tags or commits
+    #
+    # @example
+    #   Gitlab.compare(42, 'master', 'feature/branch')
+    #   Gitlab.repo_compare(42, 'master', 'feature/branch')
+    #
+    # @param [Integer] project The ID of a project.
+    # @param [String] the commit SHA or branch name of from branch
+    # @param [String] the commit SHA or branch name of to branch
+    # @retuen [Gitlab::ObjectifiedHash]
+    def compare(project, from, to)
+      get("/projects/#{project}/repository/compare?from=#{from}&to=#{to}")
+    end
+    alias_method :repo_compare, :compare
   end
 end

spec/fixtures/compare_merge_request_diff.json

@@ -0,0 +1,31 @@
+
+{
+  "commit": {
+    "id": "12d65c8dd2b2676fa3ac47d955accc085a37a9c1",
+    "short_id": "12d65c8dd2b",
+    "title": "JS fix",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2014-02-27T10:27:00+02:00"
+  },
+  "commits": [{
+    "id": "12d65c8dd2b2676fa3ac47d955accc085a37a9c1",
+    "short_id": "12d65c8dd2b",
+    "title": "JS fix",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2014-02-27T10:27:00+02:00"
+  }],
+  "diffs": [{
+    "old_path": "files/js/application.js",
+    "new_path": "files/js/application.js",
+    "a_mode": null,
+    "b_mode": "100644",
+    "diff": "--- a/files/js/application.js\n+++ b/files/js/application.js\n@@ -24,8 +24,10 @@\n //= require g.raphael-min\n //= require g.bar-min\n //= require branch-graph\n-//= require highlightjs.min\n-//= require ace/ace\n //= require_tree .\n //= require d3\n //= require underscore\n+\n+function fix() { \n+  alert(\"Fixed\")\n+}",
+    "new_file": false,
+    "renamed_file": false,
+    "deleted_file": false
+  }],
+  "compare_timeout": false,
+  "compare_same_ref": false
+}

spec/gitlab/client/repositories_spec.rb

@@ -8,6 +8,7 @@
   it { should respond_to :repo_commits }
   it { should respond_to :repo_commit }
   it { should respond_to :repo_commit_diff }
+  it { should respond_to :repo_compare}
 
   describe ".tags" do
     before do
@@ -89,4 +90,16 @@
       expect(@diff.new_path).to eq("doc/update/5.4-to-6.0.md")
     end
   end
+
+  describe ".compare" do
+    before do
+      stub_get("/projects/3/repository/compare?from=master&to=feature", "compare_merge_request_diff")
+      @diff = Gitlab.compare(3, 'master', 'feature')
+    end
+
+    it "should get diffs of a merge request" do
+      expect(@diff.diffs).to be_kind_of Array
+      expect(@diff.diffs.last["new_path"]).to eq "files/js/application.js"
+    end
+  end
 end