API: Ability to cherry-pick a commit

changelogs/unreleased/api-cherry-pick.yml

+---
+title: 'API: Ability to cherry pick a commit'
+merge_request: 8047
+author: Robert Schilling

doc/api/commits.md

@@ -183,6 +183,44 @@ Example response:
 }
 ```
+## Cherry pick a commit
+
+> [Introduced][ce-8047] in GitLab 8.15.
+
+Cherry picks a commit to a given branch.
+
+```
+POST /projects/:id/repository/commits/:sha/cherry_pick
+```
+
+Parameters:
+
+| Attribute | Type | Required | Description |
+| --------- | ---- | -------- | ----------- |
+| `id`      | integer/string | yes | The ID of a project or NAMESPACE/PROJECT_NAME owned by the authenticated user
+| `sha` | string | yes | The commit hash  |
+| `branch` | string | yes | The name of the branch  |
+
+```bash
+curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" --form "branch=master" "https://gitlab.example.com/api/v3/projects/5/repository/commits/master/cherry_pick"
+```
+
+Example response:
+
+```json
+{
+  "id": "8b090c1b79a14f2bd9e8a738f717824ff53aebad",
+  "short_id": "8b090c1b",
+  "title": "Feature added",
+  "author_name": "Dmitriy Zaporozhets",
+  "author_email": "dmitriy.zaporozhets@gmail.com",
+  "created_at": "2016-12-12T20:10:39.000+01:00",
+  "committer_name": "Administrator",
+  "committer_email": "admin@example.com",
+  "message": "Feature added\n\nSigned-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>\n"
+}
+```
+
 ## Get the diff of a commit
 Get the diff of a commit in a project.
@@ -438,3 +476,4 @@ Example response:
 ```
 [ce-6096]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6096 "Multi-file commit"
+[ce-8047]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8047

lib/api/commits.rb

 require 'mime/types'
 module API
-  # Projects commits API
   class Commits < Grape::API
     include PaginationParams
@@ -121,6 +120,41 @@ module API
         present paginate(notes), with: Entities::CommitNote
       end
+      desc 'Cherry pick commit into a branch' do
+        detail 'This feature was introduced in GitLab 8.15'
+        success Entities::RepoCommit
+      end
+      params do
+        requires :sha, type: String, desc: 'A commit sha to be cherry picked'
+        requires :branch, type: String, desc: 'The name of the branch'
+      end
+      post ':id/repository/commits/:sha/cherry_pick' do
+        authorize! :push_code, user_project
+
+        commit = user_project.commit(params[:sha])
+        not_found!('Commit') unless commit
+
+        branch = user_project.repository.find_branch(params[:branch])
+        not_found!('Branch') unless branch
+
+        commit_params = {
+          commit: commit,
+          create_merge_request: false,
+          source_project: user_project,
+          source_branch: commit.cherry_pick_branch_name,
+          target_branch: params[:branch]
+        }
+
+        result = ::Commits::CherryPickService.new(user_project, current_user, commit_params).execute
+
+        if result[:status] == :success
+          branch = user_project.repository.find_branch(params[:branch])
+          present user_project.repository.commit(branch.dereferenced_target), with: Entities::RepoCommit
+        else
+          render_api_error!(result[:message], 400)
+        end
+      end
+
       desc 'Post comment to commit' do
         success Entities::CommitNote
       end

spec/requests/api/commits_spec.rb

@@ -456,6 +456,76 @@ describe API::Commits, api: true  do
     end
   end
+  describe 'POST :id/repository/commits/:sha/cherry_pick' do
+    let(:master_pickable_commit)  { project.commit('7d3b0f7cff5f37573aea97cebfd5692ea1689924') }
+
+    context 'authorized user' do
+      it 'cherry picks a commit' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user), branch: 'master'
+
+        expect(response).to have_http_status(201)
+        expect(json_response['title']).to eq(master_pickable_commit.title)
+        expect(json_response['message']).to eq(master_pickable_commit.message)
+        expect(json_response['author_name']).to eq(master_pickable_commit.author_name)
+        expect(json_response['committer_name']).to eq(user.name)
+      end
+
+      it 'returns 400 if commit is already included in the target branch' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user), branch: 'markdown'
+
+        expect(response).to have_http_status(400)
+        expect(json_response['message']).to eq('Sorry, we cannot cherry-pick this commit automatically.
+                     It may have already been cherry-pick, or a more recent commit may have updated some of its content.')
+      end
+
+      it 'returns 400 if you are not allowed to push to the target branch' do
+        project.team << [user2, :developer]
+        protected_branch = create(:protected_branch, project: project, name: 'feature')
+
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user2), branch: 'feature'
+
+        expect(response).to have_http_status(400)
+        expect(json_response['message']).to eq('You are not allowed to push into this branch')
+      end
+
+      it 'returns 400 for missing parameters' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user)
+
+        expect(response).to have_http_status(400)
+        expect(json_response['error']).to eq('branch is missing')
+      end
+
+      it 'returns 404 if commit is not found' do
+        post api("/projects/#{project.id}/repository/commits/abcd0123/cherry_pick", user), branch: 'master'
+
+        expect(response).to have_http_status(404)
+        expect(json_response['message']).to eq('404 Commit Not Found')
+      end
+
+      it 'returns 404 if branch is not found' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user), branch: 'foo'
+
+        expect(response).to have_http_status(404)
+        expect(json_response['message']).to eq('404 Branch Not Found')
+      end
+
+      it 'returns 400 for missing parameters' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick", user)
+
+        expect(response).to have_http_status(400)
+        expect(json_response['error']).to eq('branch is missing')
+      end
+    end
+
+    context 'unauthorized user' do
+      it 'does not cherry pick the commit' do
+        post api("/projects/#{project.id}/repository/commits/#{master_pickable_commit.id}/cherry_pick"), branch: 'master'
+
+        expect(response).to have_http_status(401)
+      end
+    end
+  end
+
   describe 'Post comment to commit' do
     context 'authorized user' do
       it 'returns comment' do