Merge branch '43263-git-push-option-to-create-mr' into 'master'

Git push options to create a merge request, set target_branch and set merge when pipeline succeeds

Closes #53198 and #43263

See merge request gitlab-org/gitlab-ce!26752

app/services/ci/create_pipeline_service.rb

@@ -37,7 +37,7 @@ module Ci
         variables_attributes: params[:variables_attributes],
         project: project,
         current_user: current_user,
-        push_options: params[:push_options],
+        push_options: params[:push_options] || {},
         chat_data: params[:chat_data],
         **extra_options(options))
 

app/services/git/base_hooks_service.rb

@@ -79,7 +79,7 @@ module Git
         limited_commits,
         event_message,
         commits_count: commits_count,
-        push_options: params[:push_options] || []
+        push_options: params[:push_options] || {}
       )
 
       # Dependent code may modify the push data, so return a duplicate each time

app/services/merge_requests/push_options_handler_service.rb

+# frozen_string_literal: true
+
+module MergeRequests
+  class PushOptionsHandlerService
+    LIMIT = 10
+
+    attr_reader :branches, :changes_by_branch, :current_user, :errors,
+                :project, :push_options, :target_project
+
+    def initialize(project, current_user, changes, push_options)
+      @project = project
+      @target_project = @project.default_merge_request_target
+      @current_user = current_user
+      @branches = get_branches(changes)
+      @push_options = push_options
+      @errors = []
+    end
+
+    def execute
+      validate_service
+      return self if errors.present?
+
+      branches.each do |branch|
+        execute_for_branch(branch)
+      rescue Gitlab::Access::AccessDeniedError
+        errors << 'User access was denied'
+      rescue StandardError => e
+        Gitlab::AppLogger.error(e)
+        errors << 'An unknown error occurred'
+      end
+
+      self
+    end
+
+    private
+
+    def get_branches(raw_changes)
+      Gitlab::ChangesList.new(raw_changes).map do |changes|
+        next unless Gitlab::Git.branch_ref?(changes[:ref])
+
+        # Deleted branch
+        next if Gitlab::Git.blank_ref?(changes[:newrev])
+
+        # Default branch
+        branch_name = Gitlab::Git.branch_name(changes[:ref])
+        next if branch_name == target_project.default_branch
+
+        branch_name
+      end.compact.uniq
+    end
+
+    def validate_service
+      errors << 'User is required' if current_user.nil?
+
+      unless target_project.merge_requests_enabled?
+        errors << "Merge requests are not enabled for project #{target_project.full_path}"
+      end
+
+      if branches.size > LIMIT
+        errors << "Too many branches pushed (#{branches.size} were pushed, limit is #{LIMIT})"
+      end
+
+      if push_options[:target] && !target_project.repository.branch_exists?(push_options[:target])
+        errors << "Branch #{push_options[:target]} does not exist"
+      end
+    end
+
+    # Returns a Hash of branch => MergeRequest
+    def merge_requests
+      @merge_requests ||= MergeRequest.from_project(target_project)
+                                      .opened
+                                      .from_source_branches(branches)
+                                      .index_by(&:source_branch)
+    end
+
+    def execute_for_branch(branch)
+      merge_request = merge_requests[branch]
+
+      if merge_request
+        update!(merge_request)
+      else
+        create!(branch)
+      end
+    end
+
+    def create!(branch)
+      unless push_options[:create]
+        errors << "A merge_request.create push option is required to create a merge request for branch #{branch}"
+        return
+      end
+
+      # Use BuildService to assign the standard attributes of a merge request
+      merge_request = ::MergeRequests::BuildService.new(
+        project,
+        current_user,
+        create_params(branch)
+      ).execute
+
+      unless merge_request.errors.present?
+        merge_request = ::MergeRequests::CreateService.new(
+          project,
+          current_user,
+          merge_request.attributes
+        ).execute
+      end
+
+      collect_errors_from_merge_request(merge_request) unless merge_request.persisted?
+    end
+
+    def update!(merge_request)
+      merge_request = ::MergeRequests::UpdateService.new(
+        target_project,
+        current_user,
+        update_params
+      ).execute(merge_request)
+
+      collect_errors_from_merge_request(merge_request) unless merge_request.valid?
+    end
+
+    def create_params(branch)
+      params = {
+        assignee: current_user,
+        source_branch: branch,
+        source_project: project,
+        target_branch: push_options[:target] || target_project.default_branch,
+        target_project: target_project
+      }
+
+      if push_options.key?(:merge_when_pipeline_succeeds)
+        params.merge!(
+          merge_when_pipeline_succeeds: push_options[:merge_when_pipeline_succeeds],
+          merge_user: current_user
+        )
+      end
+
+      params
+    end
+
+    def update_params
+      params = {}
+
+      if push_options.key?(:merge_when_pipeline_succeeds)
+        params.merge!(
+          merge_when_pipeline_succeeds: push_options[:merge_when_pipeline_succeeds],
+          merge_user: current_user
+        )
+      end
+
+      if push_options.key?(:target)
+        params[:target_branch] = push_options[:target]
+      end
+
+      params
+    end
+
+    def collect_errors_from_merge_request(merge_request)
+      merge_request.errors.full_messages.each do |error|
+        errors << error
+      end
+    end
+  end
+end

app/workers/post_receive.rb

@@ -3,7 +3,7 @@
 class PostReceive
   include ApplicationWorker
 
-  def perform(gl_repository, identifier, changes, push_options = [])
+  def perform(gl_repository, identifier, changes, push_options = {})
     project, repo_type = Gitlab::GlRepository.parse(gl_repository)
 
     if project.nil?

changelogs/unreleased/43263-git-push-option-to-create-mr.yml

+---
+title: Allow merge requests to be created via git push options
+merge_request: 26752
+author:
+type: added

changelogs/unreleased/53198-git-push-option-merge-when-pipeline-succeeds.yml

+---
+title: Allow merge requests to be set to merge when pipeline succeeds via git push
+  options
+merge_request: 26842
+author:
+type: added

doc/user/project/merge_requests/index.md

@@ -219,6 +219,64 @@ apply the patches. The target branch can be specified using the
 [`/target_branch` quick action](../quick_actions.md). If the source
 branch already exists, the patches will be applied on top of it.
 
+## Git push options
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26752) in GitLab 11.10.
+
+NOTE: **Note:**
+Git push options are only available with Git 2.10 or newer.
+
+GitLab supports using
+[Git push options](https://git-scm.com/docs/git-push#Documentation/git-push.txt--oltoptiongt)
+to perform the following actions against merge requests at the same time
+as pushing changes:
+
+- Create a new merge request for the pushed branch.
+- Set the target of the merge request to a particular branch.
+- Set the merge request to merge when its pipeline succeeds.
+
+### Create a new merge request using git push options
+
+To create a new merge request for a branch, use the
+`merge_request.create` push option:
+
+```sh
+git push -o merge_request.create
+```
+
+### Set the target branch of a merge request using git push options
+
+To update an existing merge request's target branch, use the
+`merge_request.target=<branch_name>` push option:
+
+```sh
+git push -o merge_request.target=branch_name
+```
+
+You can also create a merge request and set its target branch at the
+same time using a `-o` flag per push option:
+
+```sh
+git push -o merge_request.create -o merge_request.target=branch_name
+```
+
+### Set merge when pipeline succeeds using git push options
+
+To set an existing merge request to
+[merge when its pipeline succeeds](merge_when_pipeline_succeeds.md), use
+the `merge_request.merge_when_pipeline_succeeds` push option:
+
+```sh
+git push -o merge_request.merge_when_pipeline_succeeds
+```
+
+You can also create a merge request and set it to merge when its
+pipeline succeeds at the same time using a `-o` flag per push option:
+
+```sh
+git push -o merge_request.create -o merge_request.merge_when_pipeline_succeeds
+```
+
 ## Find the merge request that introduced a change
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/2383) in GitLab 10.5.

lib/api/helpers/internal_helpers.rb

@@ -43,6 +43,28 @@ module API
         ::MergeRequests::GetUrlsService.new(project).execute(params[:changes])
       end
 
+      def process_mr_push_options(push_options, project, user, changes)
+        output = {}
+
+        service = ::MergeRequests::PushOptionsHandlerService.new(
+          project,
+          user,
+          changes,
+          push_options
+        ).execute
+
+        if service.errors.present?
+          output[:warnings] = push_options_warning(service.errors.join("\n\n"))
+        end
+
+        output
+      end
+
+      def push_options_warning(warning)
+        options = Array.wrap(params[:push_options]).map { |p| "'#{p}'" }.join(' ')
+        "Error encountered with push options #{options}: #{warning}"
+      end
+
       def redis_ping
         result = Gitlab::Redis::SharedState.with { |redis| redis.ping }
 

lib/api/internal.rb

@@ -256,19 +256,27 @@ module API
       post '/post_receive' do
         status 200
 
+        output = {} # Messages to gitlab-shell
+        user = identify(params[:identifier])
+        project = Gitlab::GlRepository.parse(params[:gl_repository]).first
+        push_options = Gitlab::PushOptions.new(params[:push_options])
+
         PostReceive.perform_async(params[:gl_repository], params[:identifier],
-          params[:changes], params[:push_options].to_a)
+          params[:changes], push_options.as_json)
+
+        if Feature.enabled?(:mr_push_options, default_enabled: true)
+          mr_options = push_options.get(:merge_request)
+          output.merge!(process_mr_push_options(mr_options, project, user, params[:changes])) if mr_options.present?
+        end
+
         broadcast_message = BroadcastMessage.current&.last&.message
         reference_counter_decreased = Gitlab::ReferenceCounter.new(params[:gl_repository]).decrease
 
-        output = {
-          merge_request_urls: merge_request_urls,
+        output.merge!(
           broadcast_message: broadcast_message,
-          reference_counter_decreased: reference_counter_decreased
-        }
-
-        project = Gitlab::GlRepository.parse(params[:gl_repository]).first
-        user = identify(params[:identifier])
+          reference_counter_decreased: reference_counter_decreased,
+          merge_request_urls: merge_request_urls
+        )
 
         # A user is not guaranteed to be returned; an orphaned write deploy
         # key could be used

lib/gitlab/ci/pipeline/chain/skip.rb

@@ -8,7 +8,6 @@ module Gitlab
           include ::Gitlab::Utils::StrongMemoize
 
           SKIP_PATTERN = /\[(ci[ _-]skip|skip[ _-]ci)\]/i
-          SKIP_PUSH_OPTION = 'ci.skip'
 
           def perform!
             if skipped?
@@ -35,7 +34,8 @@ module Gitlab
           end
 
           def push_option_skips_ci?
-            !!(@command.push_options&.include?(SKIP_PUSH_OPTION))
+            @command.push_options.present? &&
+              @command.push_options.deep_symbolize_keys.dig(:ci, :skip).present?
           end
         end
       end

lib/gitlab/data_builder/push.rb

@@ -32,10 +32,7 @@ module Gitlab
             }
           ],
           total_commits_count: 1,
-          push_options: [
-            "ci.skip",
-            "custom option"
-          ]
+          push_options: { ci: { skip: true } }
         }.freeze
 
       # Produce a hash of post-receive data
@@ -57,11 +54,11 @@ module Gitlab
       #   },
       #   commits: Array,
       #   total_commits_count: Fixnum,
-      #   push_options: Array
+      #   push_options: Hash
       # }
       #
       # rubocop:disable Metrics/ParameterLists
-      def build(project, user, oldrev, newrev, ref, commits = [], message = nil, commits_count: nil, push_options: [])
+      def build(project, user, oldrev, newrev, ref, commits = [], message = nil, commits_count: nil, push_options: {})
         commits = Array(commits)
 
         # Total commits count

lib/gitlab/git_post_receive.rb

@@ -5,7 +5,7 @@ module Gitlab
     include Gitlab::Identifier
     attr_reader :project, :identifier, :changes, :push_options
 
-    def initialize(project, identifier, changes, push_options)
+    def initialize(project, identifier, changes, push_options = {})
       @project = project
       @identifier = identifier
       @changes = deserialize_changes(changes)

lib/gitlab/push_options.rb

+# frozen_string_literal: true
+
+module Gitlab
+  class PushOptions
+    VALID_OPTIONS = HashWithIndifferentAccess.new({
+      merge_request: {
+        keys: [:create, :merge_when_pipeline_succeeds, :target]
+      },
+      ci: {
+        keys: [:skip]
+      }
+    }).freeze
+
+    NAMESPACE_ALIASES = HashWithIndifferentAccess.new({
+      mr: :merge_request
+    }).freeze
+
+    OPTION_MATCHER = /(?<namespace>[^\.]+)\.(?<key>[^=]+)=?(?<value>.*)/
+
+    attr_reader :options
+
+    def initialize(options = [])
+      @options = parse_options(options)
+    end
+
+    def get(*args)
+      options.dig(*args)
+    end
+
+    # Allow #to_json serialization
+    def as_json(*_args)
+      options
+    end
+
+    private
+
+    def parse_options(raw_options)
+      options = HashWithIndifferentAccess.new
+
+      Array.wrap(raw_options).each do |option|
+        namespace, key, value = parse_option(option)
+
+        next if [namespace, key].any?(&:nil?)
+
+        options[namespace] ||= HashWithIndifferentAccess.new
+        options[namespace][key] = value
+      end
+
+      options
+    end
+
+    def parse_option(option)
+      parts = OPTION_MATCHER.match(option)
+      return unless parts
+
+      namespace, key, value = parts.values_at(:namespace, :key, :value).map(&:strip)
+      namespace = NAMESPACE_ALIASES[namespace] if NAMESPACE_ALIASES[namespace]
+      value = value.presence || true
+
+      return unless valid_option?(namespace, key)
+
+      [namespace, key, value]
+    end
+
+    def valid_option?(namespace, key)
+      keys = VALID_OPTIONS.dig(namespace, :keys)
+      keys && keys.include?(key.to_sym)
+    end
+  end
+end

spec/lib/gitlab/push_options_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::PushOptions do
+  describe 'namespace and key validation' do
+    it 'ignores unrecognised namespaces' do
+      options = described_class.new(['invalid.key=value'])
+
+      expect(options.get(:invalid)).to eq(nil)
+    end
+
+    it 'ignores unrecognised keys' do
+      options = described_class.new(['merge_request.key=value'])
+
+      expect(options.get(:merge_request)).to eq(nil)
+    end
+
+    it 'ignores blank keys' do
+      options = described_class.new(['merge_request'])
+
+      expect(options.get(:merge_request)).to eq(nil)
+    end
+
+    it 'parses recognised namespace and key pairs' do
+      options = described_class.new(['merge_request.target=value'])
+
+      expect(options.get(:merge_request)).to include({
+        target: 'value'
+      })
+    end
+  end
+
+  describe '#get' do
+    it 'can emulate Hash#dig' do
+      options = described_class.new(['merge_request.target=value'])
+
+      expect(options.get(:merge_request, :target)).to eq('value')
+    end
+  end
+
+  describe '#as_json' do
+    it 'returns all options' do
+      options = described_class.new(['merge_request.target=value'])
+
+      expect(options.as_json).to include(
+        merge_request: {
+          target: 'value'
+        }
+      )
+    end
+  end
+
+  it 'can parse multiple push options' do
+    options = described_class.new([
+      'merge_request.create',
+      'merge_request.target=value'
+    ])
+
+    expect(options.get(:merge_request)).to include({
+      create: true,
+      target: 'value'
+    })
+    expect(options.get(:merge_request, :create)).to eq(true)
+    expect(options.get(:merge_request, :target)).to eq('value')
+  end
+
+  it 'stores options internally as a HashWithIndifferentAccess' do
+    options = described_class.new([
+      'merge_request.create'
+    ])
+
+    expect(options.get('merge_request', 'create')).to eq(true)
+    expect(options.get(:merge_request, :create)).to eq(true)
+  end
+
+  it 'selects the last option when options contain duplicate namespace and key pairs' do
+    options = described_class.new([
+      'merge_request.target=value1',
+      'merge_request.target=value2'
+    ])
+
+    expect(options.get(:merge_request, :target)).to eq('value2')
+  end
+
+  it 'defaults values to true' do
+    options = described_class.new(['merge_request.create'])
+
+    expect(options.get(:merge_request, :create)).to eq(true)
+  end
+
+  it 'expands aliases' do
+    options = described_class.new(['mr.target=value'])
+
+    expect(options.get(:merge_request, :target)).to eq('value')
+  end
+
+  it 'forgives broken push options' do
+    options = described_class.new(['merge_request . target = value'])
+
+    expect(options.get(:merge_request, :target)).to eq('value')
+  end
+end

spec/requests/api/internal_spec.rb

@@ -888,8 +888,10 @@ describe API::Internal do
       }
     end
 
+    let(:branch_name) { 'feature' }
+
     let(:changes) do
-      "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/new_branch"
+      "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{branch_name}"
     end
 
     let(:push_options) do
@@ -905,9 +907,9 @@ describe API::Internal do
 
     it 'enqueues a PostReceive worker job' do
       expect(PostReceive).to receive(:perform_async)
-        .with(gl_repository, identifier, changes, push_options)
+        .with(gl_repository, identifier, changes, { ci: { skip: true } })
 
-      post api("/internal/post_receive"), params: valid_params
+      post api('/internal/post_receive'), params: valid_params
     end
 
     it 'decreases the reference counter and returns the result' do
@@ -915,17 +917,17 @@ describe API::Internal do
         .and_return(reference_counter)
       expect(reference_counter).to receive(:decrease).and_return(true)
 
-      post api("/internal/post_receive"), params: valid_params
+      post api('/internal/post_receive'), params: valid_params
 
       expect(json_response['reference_counter_decreased']).to be(true)
     end
 
     it 'returns link to create new merge request' do
-      post api("/internal/post_receive"), params: valid_params
+      post api('/internal/post_receive'), params: valid_params
 
       expect(json_response['merge_request_urls']).to match [{
-        "branch_name" => "new_branch",
-        "url" => "http://#{Gitlab.config.gitlab.host}/#{project.namespace.name}/#{project.path}/merge_requests/new?merge_request%5Bsource_branch%5D=new_branch",
+        "branch_name" => branch_name,
+        "url" => "http://#{Gitlab.config.gitlab.host}/#{project.namespace.name}/#{project.path}/merge_requests/new?merge_request%5Bsource_branch%5D=#{branch_name}",
         "new_merge_request" => true
       }]
     end
@@ -933,16 +935,87 @@ describe API::Internal do
     it 'returns empty array if printing_merge_request_link_enabled is false' do
       project.update!(printing_merge_request_link_enabled: false)
 
-      post api("/internal/post_receive"), params: valid_params
+      post api('/internal/post_receive'), params: valid_params
 
       expect(json_response['merge_request_urls']).to eq([])
     end
 
+    it 'does not invoke MergeRequests::PushOptionsHandlerService' do
+      expect(MergeRequests::PushOptionsHandlerService).not_to receive(:new)
+
+      post api('/internal/post_receive'), params: valid_params
+    end
+
+    context 'when there are merge_request push options' do
+      before do
+        valid_params[:push_options] = ['merge_request.create']
+      end
+
+      it 'invokes MergeRequests::PushOptionsHandlerService' do
+        expect(MergeRequests::PushOptionsHandlerService).to receive(:new)
+
+        post api('/internal/post_receive'), params: valid_params
+      end
+
+      it 'creates a new merge request' do
+        expect do
+          post api('/internal/post_receive'), params: valid_params
+        end.to change { MergeRequest.count }.by(1)
+      end
+
+      it 'links to the newly created merge request' do
+        post api('/internal/post_receive'), params: valid_params
+
+        expect(json_response['merge_request_urls']).to match [{
+          'branch_name' => branch_name,
+          'url' => "http://#{Gitlab.config.gitlab.host}/#{project.namespace.name}/#{project.path}/merge_requests/1",
+          'new_merge_request' => false
+        }]
+      end
+
+      it 'adds errors on the service instance to warnings' do
+        expect_any_instance_of(
+          MergeRequests::PushOptionsHandlerService
+        ).to receive(:errors).at_least(:once).and_return(['my error'])
+
+        post api('/internal/post_receive'), params: valid_params
+
+        expect(json_response['warnings']).to eq('Error encountered with push options \'merge_request.create\': my error')
+      end
+
+      it 'adds ActiveRecord errors on invalid MergeRequest records to warnings' do
+        invalid_merge_request = MergeRequest.new
+        invalid_merge_request.errors.add(:base, 'my error')
+
+        expect_any_instance_of(
+          MergeRequests::CreateService
+        ).to receive(:execute).and_return(invalid_merge_request)
+
+        post api('/internal/post_receive'), params: valid_params
+
+        expect(json_response['warnings']).to eq('Error encountered with push options \'merge_request.create\': my error')
+      end
+
+      context 'when the feature is disabled' do
+        it 'does not invoke MergeRequests::PushOptionsHandlerService' do
+          Feature.disable(:mr_push_options)
+
+          expect(MergeRequests::PushOptionsHandlerService).to receive(:new)
+
+          expect do
+            post api('/internal/post_receive'), params: valid_params
+          end.not_to change { MergeRequest.count }
+
+          Feature.enable(:mr_push_options)
+        end
+      end
+    end
+
     context 'broadcast message exists' do
       let!(:broadcast_message) { create(:broadcast_message, starts_at: 1.day.ago, ends_at: 1.day.from_now ) }
 
       it 'returns one broadcast message' do
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
         expect(json_response['broadcast_message']).to eq(broadcast_message.message)
@@ -951,7 +1024,7 @@ describe API::Internal do
 
     context 'broadcast message does not exist' do
       it 'returns empty string' do
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
         expect(json_response['broadcast_message']).to eq(nil)
@@ -962,7 +1035,7 @@ describe API::Internal do
       it 'returns empty string' do
         allow(BroadcastMessage).to receive(:current).and_return(nil)
 
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
         expect(json_response['broadcast_message']).to eq(nil)
@@ -974,7 +1047,7 @@ describe API::Internal do
         project_moved = Gitlab::Checks::ProjectMoved.new(project, user, 'http', 'foo/baz')
         project_moved.add_message
 
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
         expect(json_response["redirected_message"]).to be_present
@@ -987,7 +1060,7 @@ describe API::Internal do
         project_created = Gitlab::Checks::ProjectCreated.new(project, user, 'http')
         project_created.add_message
 
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
         expect(json_response["project_created_message"]).to be_present
@@ -999,7 +1072,7 @@ describe API::Internal do
       it 'does not try to notify that project moved' do
         allow_any_instance_of(Gitlab::Identifier).to receive(:identify).and_return(nil)
 
-        post api("/internal/post_receive"), params: valid_params
+        post api('/internal/post_receive'), params: valid_params
 
         expect(response).to have_gitlab_http_status(200)
       end

spec/services/ci/create_pipeline_service_spec.rb

@@ -418,8 +418,7 @@ describe Ci::CreatePipelineService do
 
     context 'when push options contain ci.skip' do
       let(:push_options) do
-        ['ci.skip',
-         'another push option']
+        { 'ci' => { 'skip' => true } }
       end
 
       it 'creates a pipline in the skipped state' do

spec/services/merge_requests/push_options_handler_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MergeRequests::PushOptionsHandlerService do
+  include ProjectForksHelper
+
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :public, :repository) }
+  let(:forked_project) { fork_project(project, user, repository: true) }
+  let(:service) { described_class.new(project, user, changes, push_options) }
+  let(:source_branch) { 'fix' }
+  let(:target_branch) { 'feature' }
+  let(:new_branch_changes) { "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+  let(:existing_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+  let(:deleted_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 #{Gitlab::Git::BLANK_SHA} refs/heads/#{source_branch}" }
+  let(:default_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{project.default_branch}" }
+
+  before do
+    project.add_developer(user)
+  end
+
+  shared_examples_for 'a service that can create a merge request' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'creates a merge request' do
+      expect { service.execute }.to change { MergeRequest.count }.by(1)
+    end
+
+    it 'sets the correct target branch' do
+      branch = push_options[:target] || project.default_branch
+
+      service.execute
+
+      expect(last_mr.target_branch).to eq(branch)
+    end
+
+    it 'assigns the MR to the user' do
+      service.execute
+
+      expect(last_mr.assignee).to eq(user)
+    end
+
+    context 'when project has been forked' do
+      let(:forked_project) { fork_project(project, user, repository: true) }
+      let(:service) { described_class.new(forked_project, user, changes, push_options) }
+
+      before do
+        allow(forked_project).to receive(:empty_repo?).and_return(false)
+      end
+
+      it 'sets the correct source project' do
+        service.execute
+
+        expect(last_mr.source_project).to eq(forked_project)
+      end
+
+      it 'sets the correct target project' do
+        service.execute
+
+        expect(last_mr.target_project).to eq(project)
+      end
+    end
+  end
+
+  shared_examples_for 'a service that can set the target of a merge request' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'sets the target_branch' do
+      service.execute
+
+      expect(last_mr.target_branch).to eq(target_branch)
+    end
+  end
+
+  shared_examples_for 'a service that can set the merge request to merge when pipeline succeeds' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'sets merge_when_pipeline_succeeds' do
+      service.execute
+
+      expect(last_mr.merge_when_pipeline_succeeds).to eq(true)
+    end
+
+    it 'sets merge_user to the user' do
+      service.execute
+
+      expect(last_mr.merge_user).to eq(user)
+    end
+  end
+
+  shared_examples_for 'a service that does not create a merge request' do
+    it do
+      expect { service.execute }.not_to change { MergeRequest.count }
+    end
+  end
+
+  shared_examples_for 'a service that does not update a merge request' do
+    it do
+      expect { service.execute }.not_to change { MergeRequest.maximum(:updated_at) }
+    end
+  end
+
+  shared_examples_for 'a service that does nothing' do
+    include_examples 'a service that does not create a merge request'
+    include_examples 'a service that does not update a merge request'
+  end
+
+  describe '`create` push option' do
+    let(:push_options) { { create: true } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that can create a merge request'
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that can create a merge request'
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe '`merge_when_pipeline_succeeds` push option' do
+    let(:push_options) { { merge_when_pipeline_succeeds: true } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, merge_when_pipeline_succeeds: true } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+      end
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, merge_when_pipeline_succeeds: true } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+      end
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+      it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe '`target` push option' do
+    let(:push_options) { { target: target_branch } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, target: target_branch } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the target of a merge request'
+      end
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, target: target_branch } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the target of a merge request'
+      end
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+      it_behaves_like 'a service that can set the target of a merge request'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe 'multiple pushed branches' do
+    let(:push_options) { { create: true } }
+    let(:changes) do
+      [
+        new_branch_changes,
+        "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/feature_conflict"
+      ]
+    end
+
+    it 'creates a merge request per branch' do
+      expect { service.execute }.to change { MergeRequest.count }.by(2)
+    end
+
+    context 'when there are too many pushed branches' do
+      let(:limit) { MergeRequests::PushOptionsHandlerService::LIMIT }
+      let(:changes) do
+        TestEnv::BRANCH_SHA.to_a[0..limit].map do |x|
+          "#{Gitlab::Git::BLANK_SHA} #{x.first} refs/heads/#{x.last}"
+        end
+      end
+
+      it 'records an error' do
+        service.execute
+
+        expect(service.errors).to eq(["Too many branches pushed (#{limit + 1} were pushed, limit is #{limit})"])
+      end
+    end
+  end
+
+  describe 'no push options' do
+    let(:push_options) { {} }
+    let(:changes) { new_branch_changes }
+
+    it_behaves_like 'a service that does nothing'
+  end
+
+  describe 'no user' do
+    let(:user) { nil }
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      service.execute
+
+      expect(service.errors).to eq(['User is required'])
+    end
+  end
+
+  describe 'unauthorized user' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      Members::DestroyService.new(user).execute(ProjectMember.find_by!(user_id: user.id))
+
+      service.execute
+
+      expect(service.errors).to eq(['User access was denied'])
+    end
+  end
+
+  describe 'handling unexpected exceptions' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+    let(:exception) { StandardError.new('My standard error') }
+
+    def run_service_with_exception
+      allow_any_instance_of(
+        MergeRequests::BuildService
+      ).to receive(:execute).and_raise(exception)
+
+      service.execute
+    end
+
+    it 'records an error' do
+      run_service_with_exception
+
+      expect(service.errors).to eq(['An unknown error occurred'])
+    end
+
+    it 'writes to Gitlab::AppLogger' do
+      expect(Gitlab::AppLogger).to receive(:error).with(exception)
+
+      run_service_with_exception
+    end
+  end
+
+  describe 'when target is not a valid branch name' do
+    let(:push_options) { { create: true, target: 'my-branch' } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      service.execute
+
+      expect(service.errors).to eq(['Branch my-branch does not exist'])
+    end
+  end
+
+  describe 'when MRs are not enabled' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      expect(project).to receive(:merge_requests_enabled?).and_return(false)
+
+      service.execute
+
+      expect(service.errors).to eq(["Merge requests are not enabled for project #{project.full_path}"])
+    end
+  end
+
+  describe 'when MR has ActiveRecord errors' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'adds the error to its errors property' do
+      invalid_merge_request = MergeRequest.new
+      invalid_merge_request.errors.add(:base, 'my error')
+
+      expect_any_instance_of(
+        MergeRequests::CreateService
+      ).to receive(:execute).and_return(invalid_merge_request)
+
+      service.execute
+
+      expect(service.errors).to eq(['my error'])
+    end
+  end
+end