Add compare branches endpoint to API

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

doc/api/repositories.md

@@ -131,3 +131,69 @@ GET /projects/:id/repository/archive
 Parameters:
 + `id` (required) - The ID of a project
 + `sha` (optional) - The commit sha to download defaults to the tip of the default branch
+
+
+## Compare branches, tags or commits
+
+```
+GET /projects/:id/repository/compare
+```
+
+Parameters:
++ `id` (required) - The ID of a project
++ `from` (required) - the commit sha or branch name
++ `to` (required) - the commit sha or branch name
+
+
+```
+GET /projects/:id/repository/compare?from=master&to=feature
+```
+
+Response: 
+
+```json
+{
+  "commit": {
+    "id": "72e10ef47e770a95439255b2c49de722e8782106",
+    "short_id": "72e10ef47e7",
+    "title": "Add NEWFILE",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2014-05-26T16:03:54+03:00"
+  },
+  "commits": [{
+    "id": "0b4bc9a49b562e85de7cc9e834518ea6828729b9",
+    "short_id": "0b4bc9a49b5",
+    "title": "Feature added",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2014-02-27T10:26:01+02:00"
+  }, {
+    "id": "72e10ef47e770a95439255b2c49de722e8782106",
+    "short_id": "72e10ef47e7",
+    "title": "Add NEWFILE",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2014-05-26T16:03:54+03:00"
+  }],
+  "diffs": [{
+    "old_path": "NEWFILE",
+    "new_path": "NEWFILE",
+    "a_mode": null,
+    "b_mode": null,
+    "diff": "--- /dev/null\n+++ b/NEWFILE\n@@ -0,0 +1 @@\n+This is NEWFILE content\n\\ No newline at end of file",
+    "new_file": true,
+    "renamed_file": false,
+    "deleted_file": false
+  }, {
+    "old_path": "files/ruby/feature.rb",
+    "new_path": "files/ruby/feature.rb",
+    "a_mode": null,
+    "b_mode": null,
+    "diff": "--- /dev/null\n+++ b/files/ruby/feature.rb\n@@ -0,0 +1,5 @@\n+class Feature\n+  def foo\n+    puts 'bar'\n+  end\n+end",
+    "new_file": true,
+    "renamed_file": false,
+    "deleted_file": false
+  }]
+}
+```

lib/api/entities.rb

@@ -194,5 +194,22 @@ module API
     class Label < Grape::Entity
       expose :name
     end
+
+    class RepoDiff < Grape::Entity
+      expose :old_path, :new_path, :a_mode, :b_mode, :diff
+      expose :new_file, :renamed_file, :deleted_file
+    end
+
+    class Compare < Grape::Entity
+      expose :commit, using: Entities::RepoCommit do |compare, options|
+        Commit.new compare.commit
+      end
+      expose :commits, using: Entities::RepoCommit do |compare, options|
+        Commit.decorate compare.commits
+      end
+      expose :diffs, using: Entities::RepoDiff do |compare, options|
+        compare.diffs
+      end
+    end
   end
 end

lib/api/repositories.rb

@@ -15,6 +15,7 @@ module API
           not_found!
         end
       end
+
       # Get a project repository tags
       #
       # Parameters:
@@ -118,6 +119,21 @@ module API
           not_found!
         end
       end
+
+      # Compare two branches, tags or commits
+      #
+      # Parameters:
+      #   id (required) - The ID of a project
+      #   from (required) - the commit sha or branch name
+      #   to (required) - the commit sha or branch name
+      # Example Request:
+      #   GET /projects/:id/repository/compare?from=master&to=feature
+      get ':id/repository/compare' do
+        authorize! :download_code, user_project
+        compare = Gitlab::Git::Compare.new(user_project.repository.raw_repository, params[:from], params[:to], MergeRequestDiff::COMMITS_SAFE_SIZE)
+
+        present compare, with: Entities::Compare
+      end
     end
   end
 end