Merge branch 'jprovazn-rebase' into 'master'

Backport 'Rebase' feature from EE to CE

Closes #40301

See merge request gitlab-org/gitlab-ce!16071

19 files changed, 284 insertions, 3 deletions

diff --git a/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_rebase.vue b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_rebase.vue
new file mode 100644
index 00000000000..09276ba2769
--- /dev/null
+++ b/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_rebase.vue
@@ -0,0 +1,133 @@
+<script>
+  import simplePoll from '../../../lib/utils/simple_poll';
+  import eventHub from '../../event_hub';
+  import statusIcon from '../mr_widget_status_icon';
+  import loadingIcon from '../../../vue_shared/components/loading_icon.vue';
+  import Flash from '../../../flash';
+
+  export default {
+    name: 'MRWidgetRebase',
+    props: {
+      mr: {
+        type: Object,
+        required: true,
+      },
+      service: {
+        type: Object,
+        required: true,
+      },
+    },
+    components: {
+      statusIcon,
+      loadingIcon,
+    },
+    data() {
+      return {
+        isMakingRequest: false,
+        rebasingError: null,
+      };
+    },
+    computed: {
+      status() {
+        if (this.mr.rebaseInProgress || this.isMakingRequest) {
+          return 'loading';
+        }
+        if (!this.mr.canPushToSourceBranch && !this.mr.rebaseInProgress) {
+          return 'warning';
+        }
+        return 'success';
+      },
+      showDisabledButton() {
+        return ['failed', 'loading'].includes(this.status);
+      },
+    },
+    methods: {
+      rebase() {
+        this.isMakingRequest = true;
+        this.rebasingError = null;
+
+        this.service.rebase()
+          .then(() => {
+            simplePoll(this.checkRebaseStatus);
+          })
+          .catch((error) => {
+            this.rebasingError = error.merge_error;
+            this.isMakingRequest = false;
+            Flash('Something went wrong. Please try again.');
+          });
+      },
+      checkRebaseStatus(continuePolling, stopPolling) {
+        this.service.poll()
+          .then(res => res.data)
+          .then((res) => {
+            if (res.rebase_in_progress) {
+              continuePolling();
+            } else {
+              this.isMakingRequest = false;
+
+              if (res.merge_error && res.merge_error.length) {
+                this.rebasingError = res.merge_error;
+                Flash('Something went wrong. Please try again.');
+              }
+
+              eventHub.$emit('MRWidgetUpdateRequested');
+              stopPolling();
+            }
+          })
+          .catch(() => {
+            this.isMakingRequest = false;
+            Flash('Something went wrong. Please try again.');
+            stopPolling();
+          });
+      },
+    },
+  };
+</script>
+<template>
+  <div class="mr-widget-body media">
+    <status-icon
+      :status="status"
+      :show-disabled-button="showDisabledButton"
+      />
+
+    <div class="rebase-state-find-class-convention media media-body space-children">
+      <template v-if="mr.rebaseInProgress || isMakingRequest">
+        <span class="bold">
+          Rebase in progress
+        </span>
+      </template>
+      <template v-if="!mr.rebaseInProgress && !mr.canPushToSourceBranch">
+        <span class="bold">
+          Fast-forward merge is not possible.
+          Rebase the source branch onto
+          <span class="label-branch">{{mr.targetBranch}}</span>
+          to allow this merge request to be merged.
+        </span>
+      </template>
+      <template v-if="!mr.rebaseInProgress && mr.canPushToSourceBranch && !isMakingRequest">
+        <div class="accept-merge-holder clearfix js-toggle-container accept-action media space-children">
+          <button
+            type="button"
+            class="btn btn-sm btn-reopen btn-success"
+            :disabled="isMakingRequest"
+            @click="rebase">
+            <loading-icon v-if="isMakingRequest" />
+            Rebase
+          </button>
+          <span
+            v-if="!rebasingError"
+            class="bold">
+            Fast-forward merge is not possible.
+            Rebase the source branch onto the target branch or merge target
+            branch into source branch to allow this merge request to be merged.
+          </span>
+          <span
+            v-else
+            class="bold danger">
+            {{rebasingError}}
+          </span>
+        </div>
+      </template>
+    </div>
+  </div>
+</template>
diff --git a/app/assets/javascripts/vue_merge_request_widget/dependencies.js b/app/assets/javascripts/vue_merge_request_widget/dependencies.js
index 5bd8b99420a..940f3d9b2d0 100644
--- a/app/assets/javascripts/vue_merge_request_widget/dependencies.js
+++ b/app/assets/javascripts/vue_merge_request_widget/dependencies.js
@@ -32,6 +32,7 @@ export { default as UnresolvedDiscussionsState } from './components/states/mr_wi
 export { default as PipelineBlockedState } from './components/states/mr_widget_pipeline_blocked';
 export { default as PipelineFailedState } from './components/states/mr_widget_pipeline_failed';
 export { default as MergeWhenPipelineSucceedsState } from './components/states/mr_widget_merge_when_pipeline_succeeds';
+export { default as RebaseState } from './components/states/mr_widget_rebase.vue';
 export { default as AutoMergeFailed } from './components/states/mr_widget_auto_merge_failed';
 export { default as CheckingState } from './components/states/mr_widget_checking';
 export { default as MRWidgetStore } from './stores/mr_widget_store';
diff --git a/app/assets/javascripts/vue_merge_request_widget/mr_widget_options.js b/app/assets/javascripts/vue_merge_request_widget/mr_widget_options.js
index fdae06200de..2075f8e4fec 100644
--- a/app/assets/javascripts/vue_merge_request_widget/mr_widget_options.js
+++ b/app/assets/javascripts/vue_merge_request_widget/mr_widget_options.js
@@ -10,6 +10,7 @@ import {
   MergedState,
   ClosedState,
   MergingState,
+  RebaseState,
   WipState,
   ArchivedState,
   ConflictsState,
@@ -79,6 +80,7 @@ export default {
         ciEnvironmentsStatusPath: store.ciEnvironmentsStatusPath,
         statusPath: store.statusPath,
         mergeActionsContentPath: store.mergeActionsContentPath,
+        rebasePath: store.rebasePath,
       };
       return new MRWidgetService(endpoints);
     },
@@ -232,6 +234,7 @@ export default {
     'mr-widget-pipeline-failed': PipelineFailedState,
     'mr-widget-merge-when-pipeline-succeeds': MergeWhenPipelineSucceedsState,
     'mr-widget-auto-merge-failed': AutoMergeFailed,
+    'mr-widget-rebase': RebaseState,
   },
   template: `
     <div class="mr-state-widget prepend-top-default">
diff --git a/app/assets/javascripts/vue_merge_request_widget/services/mr_widget_service.js b/app/assets/javascripts/vue_merge_request_widget/services/mr_widget_service.js
index 7c0bbdd403f..fecbfec2214 100644
--- a/app/assets/javascripts/vue_merge_request_widget/services/mr_widget_service.js
+++ b/app/assets/javascripts/vue_merge_request_widget/services/mr_widget_service.js
@@ -37,6 +37,10 @@ export default class MRWidgetService {
     return axios.get(this.endpoints.mergeActionsContentPath);
   }
 
+  rebase() {
+    return axios.post(this.endpoints.rebasePath);
+  }
+
   static stopEnvironment(url) {
     return axios.post(url);
   }
diff --git a/app/assets/javascripts/vue_merge_request_widget/stores/get_state_key.js b/app/assets/javascripts/vue_merge_request_widget/stores/get_state_key.js
index 2bace3311c8..f7f0c1b6cb7 100644
--- a/app/assets/javascripts/vue_merge_request_widget/stores/get_state_key.js
+++ b/app/assets/javascripts/vue_merge_request_widget/stores/get_state_key.js
@@ -25,6 +25,8 @@ export default function deviseState(data) {
     return this.mergeError ? stateKey.autoMergeFailed : stateKey.mergeWhenPipelineSucceeds;
   } else if (!this.canMerge) {
     return stateKey.notAllowedToMerge;
+  } else if (this.shouldBeRebased) {
+    return stateKey.rebase;
   } else if (this.canBeMerged) {
     return stateKey.readyToMerge;
   }
diff --git a/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js b/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js
index 474c17ec133..ed004b3bb08 100644
--- a/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js
+++ b/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js
@@ -26,6 +26,7 @@ export default class MergeRequestStore {
     this.divergedCommitsCount = data.diverged_commits_count;
     this.pipeline = data.pipeline || {};
     this.deployments = this.deployments || data.deployments || [];
+    this.initRebase(data);
 
     if (data.issues_links) {
       const links = data.issues_links;
@@ -124,6 +125,13 @@ export default class MergeRequestStore {
     return this.state === stateKey.nothingToMerge;
   }
 
+  initRebase(data) {
+    this.canPushToSourceBranch = data.can_push_to_source_branch;
+    this.rebaseInProgress = data.rebase_in_progress;
+    this.approvalsLeft = !data.approved;
+    this.rebasePath = data.rebase_path;
+  }
+
   static buildMetrics(metrics) {
     if (!metrics) {
       return {};
diff --git a/app/assets/javascripts/vue_merge_request_widget/stores/state_maps.js b/app/assets/javascripts/vue_merge_request_widget/stores/state_maps.js
index de980c175fb..29d5bd4a1da 100644
--- a/app/assets/javascripts/vue_merge_request_widget/stores/state_maps.js
+++ b/app/assets/javascripts/vue_merge_request_widget/stores/state_maps.js
@@ -17,6 +17,7 @@ const stateToComponentMap = {
   failedToMerge: 'mr-widget-failed-to-merge',
   autoMergeFailed: 'mr-widget-auto-merge-failed',
   shaMismatch: 'mr-widget-sha-mismatch',
+  rebase: 'mr-widget-rebase',
 };
 
 const statesToShowHelpWidget = [
@@ -29,6 +30,7 @@ const statesToShowHelpWidget = [
   'pipelineFailed',
   'pipelineBlocked',
   'autoMergeFailed',
+  'rebase',
 ];
 
 export const stateKey = {
@@ -46,6 +48,7 @@ export const stateKey = {
   mergeWhenPipelineSucceeds: 'mergeWhenPipelineSucceeds',
   notAllowedToMerge: 'notAllowedToMerge',
   readyToMerge: 'readyToMerge',
+  rebase: 'rebase',
 };
 
 export default {
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 6b59c8461a3..2e8a738b6d9 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -10,6 +10,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
   before_action :authorize_update_issuable!, only: [:close, :edit, :update, :remove_wip, :sort]
   before_action :set_issuables_index, only: [:index]
   before_action :authenticate_user!, only: [:assign_related_issues]
+  before_action :check_user_can_push_to_source_branch!, only: [:rebase]
 
   def index
     @merge_requests = @issuables
@@ -223,6 +224,12 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     render json: environments
   end
 
+  def rebase
+    RebaseWorker.perform_async(@merge_request.id, current_user.id)
+
+    render nothing: true, status: 200
+  end
+
   protected
 
   alias_method :subscribable_resource, :merge_request
@@ -322,4 +329,14 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     @finder_type = MergeRequestsFinder
     super
   end
+
+  def check_user_can_push_to_source_branch!
+    return access_denied! unless @merge_request.source_branch_exists?
+
+    access_check = ::Gitlab::UserAccess
+      .new(current_user, project: @merge_request.source_project)
+      .can_push_to_branch?(@merge_request.source_branch)
+
+    access_denied! unless access_check
+  end
 end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index c39789b047d..ef58816937c 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -156,6 +156,13 @@ class MergeRequest < ActiveRecord::Base
     '!'
   end
 
+  def rebase_in_progress?
+    # The source project can be deleted
+    return false unless source_project
+
+    source_project.repository.rebase_in_progress?(id)
+  end
+
   # Use this method whenever you need to make sure the head_pipeline is synced with the
   # branch head commit, for example checking if a merge request can be merged.
   # For more information check: https://gitlab.com/gitlab-org/gitlab-ce/issues/40004
@@ -607,7 +614,7 @@ class MergeRequest < ActiveRecord::Base
 
     check_if_can_be_merged
 
-    can_be_merged?
+    can_be_merged? && !should_be_rebased?
   end
 
   def mergeable_state?(skip_ci_check: false)
diff --git a/app/models/repository.rb b/app/models/repository.rb
index b1fd981965c..4bedcbfb6a2 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -1099,6 +1099,13 @@ class Repository
     @project.repository_storage_path
   end
 
+  def rebase(user, merge_request)
+    raw.rebase(user, merge_request.id, branch: merge_request.source_branch,
+                                       branch_sha: merge_request.source_branch_sha,
+                                       remote_repository: merge_request.target_project.repository.raw,
+                                       remote_branch: merge_request.target_branch)
+  end
+
   private
 
   # TODO Generice finder, later split this on finders by Ref or Oid
diff --git a/app/presenters/merge_request_presenter.rb b/app/presenters/merge_request_presenter.rb
index ab4c87c0169..c6806b7cc26 100644
--- a/app/presenters/merge_request_presenter.rb
+++ b/app/presenters/merge_request_presenter.rb
@@ -76,6 +76,12 @@ class MergeRequestPresenter < Gitlab::View::Presenter::Delegated
     end
   end
 
+  def rebase_path
+    if !rebase_in_progress? && should_be_rebased? && user_can_push_to_source_branch?
+      rebase_project_merge_request_path(project, merge_request)
+    end
+  end
+
   def target_branch_tree_path
     if target_branch_exists?
       project_tree_path(project, target_branch)
@@ -152,6 +158,10 @@ class MergeRequestPresenter < Gitlab::View::Presenter::Delegated
     user_can_collaborate_with_project? && can_be_cherry_picked?
   end
 
+  def can_push_to_source_branch?
+    source_branch_exists? && user_can_push_to_source_branch?
+  end
+
   private
 
   def conflicts
@@ -174,6 +184,14 @@ class MergeRequestPresenter < Gitlab::View::Presenter::Delegated
     end.sort.to_sentence
   end
 
+  def user_can_push_to_source_branch?
+    return false unless source_branch_exists?
+
+    ::Gitlab::UserAccess
+      .new(current_user, project: source_project)
+      .can_push_to_branch?(source_branch)
+  end
+
   def user_can_collaborate_with_project?
     can?(current_user, :push_code, project) ||
       (current_user && current_user.already_forked?(project))
diff --git a/app/serializers/merge_request_basic_entity.rb b/app/serializers/merge_request_basic_entity.rb
index d54a6516aed..e4aec977f01 100644
--- a/app/serializers/merge_request_basic_entity.rb
+++ b/app/serializers/merge_request_basic_entity.rb
@@ -4,4 +4,5 @@ class MergeRequestBasicEntity < IssuableSidebarEntity
   expose :merge_error
   expose :state
   expose :source_branch_exists?, as: :source_branch_exists
+  expose :rebase_in_progress?, as: :rebase_in_progress
 end
diff --git a/app/serializers/merge_request_widget_entity.rb b/app/serializers/merge_request_widget_entity.rb
index e905e6876c2..48cd2317f46 100644
--- a/app/serializers/merge_request_widget_entity.rb
+++ b/app/serializers/merge_request_widget_entity.rb
@@ -23,6 +23,16 @@ class MergeRequestWidgetEntity < IssuableEntity
     MergeRequestMetricsEntity.new(metrics).as_json
   end
 
+  expose :rebase_commit_sha
+  expose :rebase_in_progress?, as: :rebase_in_progress
+
+  expose :can_push_to_source_branch do |merge_request|
+    presenter(merge_request).can_push_to_source_branch?
+  end
+  expose :rebase_path do |merge_request|
+    presenter(merge_request).rebase_path
+  end
+
   # User entities
   expose :merge_user, using: UserEntity
 
diff --git a/app/services/merge_requests/rebase_service.rb b/app/services/merge_requests/rebase_service.rb
new file mode 100644
index 00000000000..0d5a25fa28e
--- /dev/null
+++ b/app/services/merge_requests/rebase_service.rb
@@ -0,0 +1,30 @@
+module MergeRequests
+  class RebaseService < MergeRequests::WorkingCopyBaseService
+    def execute(merge_request)
+      @merge_request = merge_request
+
+      if rebase
+        success
+      else
+        error('Failed to rebase. Should be done manually')
+      end
+    end
+
+    def rebase
+      if merge_request.rebase_in_progress?
+        log_error('Rebase task canceled: Another rebase is already in progress', save_message_on_model: true)
+        return false
+      end
+
+      rebase_sha = repository.rebase(current_user, merge_request)
+
+      merge_request.update_attributes(rebase_commit_sha: rebase_sha)
+
+      true
+    rescue => e
+      log_error('Failed to rebase branch:')
+      log_error(e.message, save_message_on_model: true)
+      false
+    end
+  end
+end
diff --git a/app/services/merge_requests/working_copy_base_service.rb b/app/services/merge_requests/working_copy_base_service.rb
new file mode 100644
index 00000000000..186e05bf966
--- /dev/null
+++ b/app/services/merge_requests/working_copy_base_service.rb
@@ -0,0 +1,24 @@
+module MergeRequests
+  class WorkingCopyBaseService < MergeRequests::BaseService
+    attr_reader :merge_request
+
+    def source_project
+      @source_project ||= merge_request.source_project
+    end
+
+    def target_project
+      @target_project ||= merge_request.target_project
+    end
+
+    def log_error(message, save_message_on_model: false)
+      Gitlab::GitLogger.error("#{self.class.name} error (#{merge_request.to_reference(full: true)}): #{message}")
+
+      merge_request.update(merge_error: message) if save_message_on_model
+    end
+
+    # Don't try to print expensive instance variables.
+    def inspect
+      "#<#{self.class} #{merge_request.to_reference(full: true)}>"
+    end
+  end
+end
diff --git a/app/views/projects/_merge_request_fast_forward_settings.html.haml b/app/views/projects/_merge_request_fast_forward_settings.html.haml
index 9d357293a2f..8129c72feb2 100644
--- a/app/views/projects/_merge_request_fast_forward_settings.html.haml
+++ b/app/views/projects/_merge_request_fast_forward_settings.html.haml
@@ -10,4 +10,4 @@
       No merge commits are created and all merges are fast-forwarded, which means that merging is only allowed if the branch could be fast-forwarded.
     %br
     %span.descr
-      When fast-forward merge is not possible, the user must first rebase locally.
+      When fast-forward merge is not possible, the user is given the option to rebase.
diff --git a/app/views/projects/_merge_request_rebase_settings.html.haml b/app/views/projects/_merge_request_rebase_settings.html.haml
index c52e09573a6..54e0b73d24c 100644
--- a/app/views/projects/_merge_request_rebase_settings.html.haml
+++ b/app/views/projects/_merge_request_rebase_settings.html.haml
@@ -10,4 +10,4 @@
       This way you could make sure that if this merge request would build, after merging to target branch it would also build.
     %br
     %span.descr
-      When fast-forward merge is not possible, the user must first rebase locally.
+      When fast-forward merge is not possible, the user is given the option to rebase.
diff --git a/app/workers/all_queues.yml b/app/workers/all_queues.yml
index 268b7028fd9..fafd9e5ef00 100644
--- a/app/workers/all_queues.yml
+++ b/app/workers/all_queues.yml
@@ -89,6 +89,7 @@
 - project_service
 - propagate_service_template
 - reactive_caching
+- rebase
 - repository_fork
 - repository_import
 - storage_migrator
diff --git a/app/workers/rebase_worker.rb b/app/workers/rebase_worker.rb
new file mode 100644
index 00000000000..090987778a2
--- /dev/null
+++ b/app/workers/rebase_worker.rb
@@ -0,0 +1,12 @@
+class RebaseWorker
+  include ApplicationWorker
+
+  def perform(merge_request_id, current_user_id)
+    current_user = User.find(current_user_id)
+    merge_request = MergeRequest.find(merge_request_id)
+
+    MergeRequests::RebaseService
+      .new(merge_request.source_project, current_user)
+      .execute(merge_request)
+  end
+end