Add API endpoint to fetch merge request commits list

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

CHANGELOG

@@ -7,6 +7,7 @@ v 8.3.0 (unreleased)
   - Add ignore whitespace change option to commit view
   - Fire update hook from GitLab
   - Don't show project fork event as "imported"
+  - Add API endpoint to fetch merge request commits list
 
 v 8.2.2
   - Fix 404 in redirection after removing a project (Stan Hu)

doc/api/merge_requests.md

@@ -101,6 +101,45 @@ Parameters:
 }
 ```
 
+## Get single MR commits
+
+Get a list of repository commits in a merge request.
+
+```
+GET /projects/:id/merge_request/:merge_request_id/commits
+```
+
+Parameters:
+
+- `id` (required) - The ID of a project
+- `merge_request_id` (required) - The ID of MR
+
+
+```json
+[
+  {
+    "id": "ed899a2f4b50b4370feeea94676502b42383c746",
+    "short_id": "ed899a2f4b5",
+    "title": "Replace sanitize with escape once",
+    "author_name": "Dmitriy Zaporozhets",
+    "author_email": "dzaporozhets@sphereconsultinginc.com",
+    "created_at": "2012-09-20T11:50:22+03:00",
+    "message": "Replace sanitize with escape once",
+    "allow_failure": false
+  },
+  {
+    "id": "6104942438c14ec7bd21c6cd5bd995272b3faff6",
+    "short_id": "6104942438c",
+    "title": "Sanitize for network graph",
+    "author_name": "randx",
+    "author_email": "dmitriy.zaporozhets@gmail.com",
+    "created_at": "2012-09-20T09:06:12+03:00",
+    "message": "Sanitize for network graph",
+    "allow_failure": false
+  }
+]
+```
+
 ## Get single MR changes
 
 Shows information about the merge request including its files and changes.

lib/api/merge_requests.rb

@@ -76,6 +76,22 @@ module API
         present merge_request, with: Entities::MergeRequest
       end
 
+      # Show MR commits
+      #
+      # Parameters:
+      #   id (required)               - The ID of a project
+      #   merge_request_id (required) - The ID of MR
+      #
+      # Example:
+      #   GET /projects/:id/merge_request/:merge_request_id/commits
+      #
+      get ':id/merge_request/:merge_request_id/commits' do
+        merge_request = user_project.merge_requests.
+          find(params[:merge_request_id])
+        authorize! :read_merge_request, merge_request
+        present merge_request.commits, with: Entities::RepoCommit
+      end
+
       # Show MR changes
       #
       # Parameters:

spec/requests/api/merge_requests_spec.rb

@@ -131,6 +131,23 @@ describe API::API, api: true  do
     end
   end
 
+  describe 'GET /projects/:id/merge_request/:merge_request_id/commits' do
+    context 'valid merge request' do
+      before { get api("/projects/#{project.id}/merge_request/#{merge_request.id}/commits", user) }
+      let(:commit) { merge_request.commits.first }
+
+      it { expect(response.status).to eq 200 }
+      it { expect(json_response.size).to eq(merge_request.commits.size) }
+      it { expect(json_response.first['id']).to eq(commit.id) }
+      it { expect(json_response.first['title']).to eq(commit.title) }
+    end
+
+    it 'returns a 404 when merge_request_id not found' do
+      get api("/projects/#{project.id}/merge_request/999/commits", user)
+      expect(response.status).to eq(404)
+    end
+  end
+
   describe 'GET /projects/:id/merge_request/:merge_request_id/changes' do
     it 'should return the change information of the merge_request' do
       get api("/projects/#{project.id}/merge_request/#{merge_request.id}/changes", user)