Squashed commit of the following:

commit 04b06a2293fa12660a9c213a9db27fe90b83248b
Merge: d580841d4ed a445aa0a
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Mon Dec 3 10:51:55 2018 +0900

    Merge branch 'master-ce' into fix-mr-widget-unrelated-deployment-status

commit d580841d4ed944f01e6417fa77842826843b6a04
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Fri Nov 30 18:11:04 2018 +0900

    Add environment to all_models.yml

commit 689fbe2699a3adf10804312e680fa336e4560eaf
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Fri Nov 30 17:00:35 2018 +0900

    Proper way to get uniq relationship

commit c0733c6ecd535a6a1b6243080a2226836890f479
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Fri Nov 30 16:20:40 2018 +0900

    Revert build change

commit 19dc55a8fe6e0fa575858d51144516b7fb0120de
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Fri Nov 30 16:19:18 2018 +0900

    Add uniq option

commit 0a6995f311c09b453fd0aecff2f6052de38efc27
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Fri Nov 30 16:14:30 2018 +0900

    Drop persisted_environment

commit 3f68fc783b0ee0d66e03de6d979616c4c4892118
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Wed Nov 28 13:59:04 2018 +0900

    Return empty array if pipeline is nil

commit 73801c5c3d06339e38dce7461a71285bcdbb8f45
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Tue Nov 27 16:34:47 2018 +0900

    Add changelog

commit d461699abf2835cc51949a5138e829628209dd6d
Author: Shinya Maeda <shinya@gitlab.com>
Date:   Tue Nov 27 16:32:20 2018 +0900

    Squashed commit of the following:

    commit 77ab5259605e217a39b04d2cea6204277e42d2b5
    Merge: 7ac1ed50612 2ee8c40f
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Tue Nov 27 16:31:07 2018 +0900

        Merge branch 'master-ce' into fix-mr-widget-unrelated-deployment-status

    commit 7ac1ed50612620df6408220b0a7cfcb626a04c48
    Merge: 49ba5c5aeff b55aeca2
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Mon Nov 26 20:01:43 2018 +0900

        Merge branch 'master-ce' into fix-mr-widget-unrelated-deployment-status

    commit 49ba5c5aeff3efee7b7498d443372021c3f4f8b5
    Merge: aa3fd0ff9e8 fbbe5ccd
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Mon Nov 26 15:27:36 2018 +0900

        Merge branch 'master-ce' into fix-mr-widget-unrelated-deployment-status

    commit aa3fd0ff9e8a418a233ebaa60b38c081cab50099
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Tue Nov 20 18:28:53 2018 +0900

        Fix static analysis

    commit 7afe5f37003869a73dbb297229f8533f78b82684
    Merge: e65b9580ff4 8a581d53
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Tue Nov 20 18:27:33 2018 +0900

        Merge branch 'master-ce' into fix-mr-widget-unrelated-deployment-status

    commit e65b9580ff422359113e1a4e37c212f7b13aba4d
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Mon Nov 19 17:59:48 2018 +0900

        Ignore deployments from project import/export

    commit 9eb4ddab8415c1ef61a3c646bdc4602bcf4ebe24
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Mon Nov 19 16:26:00 2018 +0900

        Add memoization

    commit 57f0bea3aaaa07b75d18e52068c532277350cda0
    Author: Shinya Maeda <shinya@gitlab.com>
    Date:   Mon Nov 19 16:21:39 2018 +0900

        Fix unrelated deployment status in MR widget

app/models/ci/pipeline.rb

@@ -26,6 +26,8 @@ module Ci
     has_many :builds, foreign_key: :commit_id, inverse_of: :pipeline
     has_many :trigger_requests, dependent: :destroy, foreign_key: :commit_id # rubocop:disable Cop/ActiveRecordDependent
     has_many :variables, class_name: 'Ci::PipelineVariable'
+    has_many :deployments, through: :builds
+    has_many :environments, -> { distinct }, through: :deployments
 
     # Merge requests for which the current pipeline is running against
     # the merge request's latest commit.
@@ -523,10 +525,6 @@ module Ci
       yaml_errors.present?
     end
 
-    def environments
-      builds.where.not(environment: nil).success.pluck(:environment).uniq
-    end
-
     # Manually set the notes for a Ci::Pipeline
     # There is no ActiveRecord relation between Ci::Pipeline and notes
     # as they are related to a commit sha. This method helps importing

app/models/environment_status.rb

@@ -12,13 +12,13 @@ class EnvironmentStatus
   delegate :deployed_at, to: :deployment, allow_nil: true
 
   def self.for_merge_request(mr, user)
-    build_environments_status(mr, user, mr.diff_head_sha)
+    build_environments_status(mr, user, mr.actual_head_pipeline)
   end
 
   def self.after_merge_request(mr, user)
     return [] unless mr.merged?
 
-    build_environments_status(mr, user, mr.merge_commit_sha)
+    build_environments_status(mr, user, mr.merge_pipeline)
   end
 
   def initialize(environment, merge_request, sha)
@@ -61,13 +61,13 @@ class EnvironmentStatus
     }
   end
 
-  def self.build_environments_status(mr, user, sha)
-    Environment.where(project_id: [mr.source_project_id, mr.target_project_id])
-               .available
-               .with_deployment(sha).map do |environment|
+  def self.build_environments_status(mr, user, pipeline)
+    return [] unless pipeline
+
+    pipeline.environments.available.map do |environment|
       next unless Ability.allowed?(user, :read_environment, environment)
 
-      EnvironmentStatus.new(environment, mr, sha)
+      EnvironmentStatus.new(environment, mr, pipeline.sha)
     end.compact
   end
   private_class_method :build_environments_status

changelogs/unreleased/fix-mr-widget-unrelated-deployment-status.yml

+---
+title: Fix unrelated deployment status in MR widget
+merge_request: 23175
+author:
+type: fixed

spec/features/merge_request/user_sees_deployment_widget_spec.rb

@@ -29,6 +29,22 @@ describe 'Merge request > User sees deployment widget', :js do
         expect(page).to have_content("Deployed to #{environment.name}")
         expect(find('.js-deploy-time')['data-original-title']).to eq(deployment.created_at.to_time.in_time_zone.to_s(:medium))
       end
+
+      context 'when a user created a new merge request with the same SHA' do
+        let(:pipeline2) { create(:ci_pipeline_without_jobs, sha: sha, project: project, ref: 'new-patch-1') }
+        let(:build2) { create(:ci_build, :success, pipeline: pipeline2) }
+        let(:environment2) { create(:environment, project: project) }
+        let!(:deployment2) { create(:deployment, environment: environment2, sha: sha, ref: 'new-patch-1', deployable: build2) }
+
+        it 'displays one environment which is related to the pipeline' do
+          visit project_merge_request_path(project, merge_request)
+          wait_for_requests
+
+          expect(page).to have_selector('.js-deployment-info', count: 1)
+          expect(page).to have_content("#{environment.name}")
+          expect(page).not_to have_content("#{environment2.name}")
+        end
+      end
     end
 
     context 'when deployment failed' do

spec/lib/gitlab/import_export/all_models.yml

@@ -121,6 +121,8 @@ pipelines:
 - artifacts
 - pipeline_schedule
 - merge_requests
+- deployments
+- environments
 pipeline_variables:
 - pipeline
 stages:

spec/models/environment_status_spec.rb

@@ -92,16 +92,12 @@ describe EnvironmentStatus do
   end
 
   describe '.build_environments_status' do
-    subject { described_class.send(:build_environments_status, merge_request, user, sha) }
+    subject { described_class.send(:build_environments_status, merge_request, user, pipeline) }
 
     let!(:build) { create(:ci_build, :deploy_to_production, pipeline: pipeline) }
     let(:environment) { build.deployment.environment }
     let(:user) { project.owner }
 
-    before do
-      build.deployment&.update!(sha: sha)
-    end
-
     context 'when environment is created on a forked project' do
       let(:project) { create(:project, :repository) }
       let(:forked) { fork_project(project, user, repository: true) }
@@ -160,6 +156,39 @@ describe EnvironmentStatus do
           expect(subject.count).to eq(0)
         end
       end
+
+      context 'when multiple deployments with the same SHA in different environments' do
+        let(:pipeline2) { create(:ci_pipeline, sha: sha, project: project) }
+        let!(:build2) { create(:ci_build, :start_review_app, pipeline: pipeline2) }
+
+        it 'returns deployments related to the head pipeline' do
+          expect(subject.count).to eq(1)
+          expect(subject[0].environment).to eq(environment)
+          expect(subject[0].merge_request).to eq(merge_request)
+          expect(subject[0].sha).to eq(sha)
+        end
+      end
+
+      context 'when multiple deployments in the same pipeline for the same environments' do
+        let!(:build2) { create(:ci_build, :deploy_to_production, pipeline: pipeline) }
+
+        it 'returns unique entries' do
+          expect(subject.count).to eq(1)
+          expect(subject[0].environment).to eq(environment)
+          expect(subject[0].merge_request).to eq(merge_request)
+          expect(subject[0].sha).to eq(sha)
+        end
+      end
+
+      context 'when environment is stopped' do
+        before do
+          environment.stop!
+        end
+
+        it 'does not return environment status' do
+          expect(subject.count).to eq(0)
+        end
+      end
     end
   end
 end