Add 'squash and rebase' feature to CE

app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue

-/*
-The squash-before-merge button is EE only, but it's located right in the middle
-of the readyToMerge state component template.
-
-If we didn't declare this component in CE, we'd need to maintain a separate copy
-of the readyToMergeState template in EE, which is pretty big and likely to change.
-
-Instead, in CE, we declare the component, but it's hidden and is configured to do nothing.
-In EE, the configuration extends this object to add a functioning squash-before-merge
-button.
-*/
-
 <script>
-  export default {};
+import Icon from '~/vue_shared/components/icon.vue';
+import eventHub from '~/vue_merge_request_widget/event_hub';
+import tooltip from '~/vue_shared/directives/tooltip';
+
+export default {
+  components: {
+    Icon,
+  },
+  directives: {
+    tooltip,
+  },
+  props: {
+    mr: {
+      type: Object,
+      required: true,
+    },
+    isMergeButtonDisabled: {
+      type: Boolean,
+      required: true,
+    },
+  },
+  data() {
+    return {
+      squashBeforeMerge: this.mr.squash,
+    };
+  },
+  methods: {
+    updateSquashModel() {
+      eventHub.$emit('MRWidgetUpdateSquash', this.squashBeforeMerge);
+    },
+  },
+};
 </script>
+
+<template>
+  <div class="accept-control inline">
+    <label class="merge-param-checkbox">
+      <input
+        type="checkbox"
+        name="squash"
+        class="qa-squash-checkbox"
+        :disabled="isMergeButtonDisabled"
+        v-model="squashBeforeMerge"
+        @change="updateSquashModel"
+      />
+      {{ __('Squash commits') }}
+    </label>
+    <a
+      :href="mr.squashBeforeMergeHelpPath"
+      data-title="About this feature"
+      data-placement="bottom"
+      target="_blank"
+      rel="noopener noreferrer nofollow"
+      data-container="body"
+      v-tooltip
+    >
+      <icon
+        name="question-o"
+      />
+    </a>
+  </div>
+</template>

app/assets/javascripts/vue_merge_request_widget/components/states/ready_to_merge.vue

@@ -6,11 +6,13 @@ import MergeRequest from '../../../merge_request';
 import Flash from '../../../flash';
 import statusIcon from '../mr_widget_status_icon.vue';
 import eventHub from '../../event_hub';
+import SquashBeforeMerge from './mr_widget_squash_before_merge.vue';
 
 export default {
   name: 'ReadyToMerge',
   components: {
     statusIcon,
+    'squash-before-merge': SquashBeforeMerge,
   },
   props: {
     mr: { type: Object, required: true },
@@ -105,6 +107,12 @@ export default {
       return this.mr.approvalsRequired ? !this.mr.isApproved : false;
     },
   },
+  created() {
+    eventHub.$on('MRWidgetUpdateSquash', this.handleUpdateSquash);
+  },
+  beforeDestroy() {
+    eventHub.$off('MRWidgetUpdateSquash', this.handleUpdateSquash);
+  },
   methods: {
     shouldShowMergeControls() {
       return this.mr.isMergeAllowed || this.shouldShowMergeWhenPipelineSucceedsText;
@@ -132,13 +140,9 @@ export default {
         commit_message: this.commitMessage,
         merge_when_pipeline_succeeds: this.setToMergeWhenPipelineSucceeds,
         should_remove_source_branch: this.removeSourceBranch === true,
+        squash: this.mr.squash,
       };
 
-      // Only truthy in EE extension of this component
-      if (this.setAdditionalParams) {
-        this.setAdditionalParams(options);
-      }
-
       this.isMakingRequest = true;
       this.service.merge(options)
         .then(res => res.data)
@@ -158,6 +162,9 @@ export default {
           new Flash('Something went wrong. Please try again.'); // eslint-disable-line
         });
     },
+    handleUpdateSquash(val) {
+      this.mr.squash = val;
+    },
     initiateMergePolling() {
       simplePoll((continuePolling, stopPolling) => {
         this.handleMergePolling(continuePolling, stopPolling);

app/assets/javascripts/vue_merge_request_widget/dependencies.js

@@ -26,7 +26,7 @@ export { default as ConflictsState } from './components/states/mr_widget_conflic
 export { default as NothingToMergeState } from './components/states/nothing_to_merge.vue';
 export { default as MissingBranchState } from './components/states/mr_widget_missing_branch.vue';
 export { default as NotAllowedState } from './components/states/mr_widget_not_allowed.vue';
-export { default as ReadyToMergeState } from 'ee/vue_merge_request_widget/components/states/mr_widget_ready_to_merge.vue';
+export { default as ReadyToMergeState } from './components/states/ready_to_merge.vue';
 export { default as ShaMismatchState } from './components/states/sha_mismatch.vue';
 export { default as UnresolvedDiscussionsState } from './components/states/unresolved_discussions.vue';
 export { default as PipelineBlockedState } from './components/states/mr_widget_pipeline_blocked.vue';
@@ -40,7 +40,7 @@ export { default as MRWidgetService } from 'ee/vue_merge_request_widget/services
 export { default as eventHub } from './event_hub';
 export { default as getStateKey } from 'ee/vue_merge_request_widget/stores/get_state_key';
 export { default as stateMaps } from 'ee/vue_merge_request_widget/stores/state_maps';
-export { default as SquashBeforeMerge } from 'ee/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue';
+export { default as SquashBeforeMerge } from './components/states/mr_widget_squash_before_merge.vue';
 export { default as notify } from '../lib/utils/notify';
 export { default as SourceBranchRemovalStatus } from './components/source_branch_removal_status.vue';
 

app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js

@@ -15,8 +15,10 @@ export default class MergeRequestStore {
     const currentUser = data.current_user;
     const pipelineStatus = data.pipeline ? data.pipeline.details.status : null;
 
-    // EE specific
     this.squash = data.squash;
+    this.squashBeforeMergeHelpPath = this.squashBeforeMergeHelpPath ||
+      data.squash_before_merge_help_path;
+    this.enableSquashBeforeMerge = this.enableSquashBeforeMerge || true;
 
     this.title = data.title;
     this.targetBranch = data.target_branch;

app/controllers/projects/merge_requests/application_controller.rb

@@ -26,6 +26,7 @@ class Projects::MergeRequests::ApplicationController < Projects::ApplicationCont
       :source_branch,
       :source_project_id,
       :state_event,
+      :squash,
       :target_branch,
       :target_project_id,
       :task_num,

app/controllers/projects/merge_requests_controller.rb

@@ -257,7 +257,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
   end
 
   def merge_params_attributes
-    [:should_remove_source_branch, :commit_message]
+    [:should_remove_source_branch, :commit_message, :squash]
   end
 
   def merge_when_pipeline_succeeds_active?

app/helpers/merge_requests_helper.rb

@@ -137,8 +137,9 @@ module MergeRequestsHelper
     {
       merge_when_pipeline_succeeds: true,
       should_remove_source_branch: true,
-      sha: merge_request.diff_head_sha
-    }.merge(merge_params_ee(merge_request))
+      sha: merge_request.diff_head_sha,
+      squash: merge_request.squash
+    }
   end
 
   def tab_link_for(merge_request, tab, options = {}, &block)
@@ -189,8 +190,4 @@ module MergeRequestsHelper
       current_user.fork_of(project)
     end
   end
-
-  def merge_params_ee(merge_request)
-    { squash: merge_request.squash }
-  end
 end

app/models/merge_request.rb

@@ -1173,4 +1173,11 @@ class MergeRequest < ActiveRecord::Base
     maintainer_push_possible? &&
       Ability.allowed?(user, :push_code, source_project)
   end
+
+  def squash_in_progress?
+    # The source project can be deleted
+    return false unless source_project
+
+    source_project.repository.squash_in_progress?(id)
+  end
 end

app/models/repository.rb

@@ -1014,6 +1014,14 @@ class Repository
     blob.data
   end
 
+  def squash(user, merge_request)
+    raw.squash(user, merge_request.id, branch: merge_request.target_branch,
+                                       start_sha: merge_request.diff_start_sha,
+                                       end_sha: merge_request.diff_head_sha,
+                                       author: merge_request.author,
+                                       message: merge_request.title)
+  end
+
   private
 
   # TODO Generice finder, later split this on finders by Ref or Oid

app/serializers/merge_request_widget_entity.rb

@@ -12,6 +12,7 @@ class MergeRequestWidgetEntity < IssuableEntity
   expose :merge_when_pipeline_succeeds
   expose :source_branch
   expose :source_project_id
+  expose :squash
   expose :target_branch
   expose :target_project_id
   expose :allow_maintainer_to_push
@@ -23,7 +24,6 @@ class MergeRequestWidgetEntity < IssuableEntity
 
   # EE-specific
   expose :approvals_before_merge
-  expose :squash
 
   expose :rebase_commit_sha
   expose :rebase_in_progress?, as: :rebase_in_progress

app/services/merge_requests/merge_service.rb

@@ -36,6 +36,19 @@ module MergeRequests
       handle_merge_error(log_message: e.message, save_message_on_model: true)
     end
 
+    def source
+      return merge_request.diff_head_sha unless merge_request.squash
+
+      squash_result = ::MergeRequests::SquashService.new(project, current_user, params).execute(merge_request)
+
+      case squash_result[:status]
+      when :success
+        squash_result[:squash_sha]
+      when :error
+        raise ::MergeRequests::MergeService::MergeError, squash_result[:message]
+      end
+    end
+
     private
 
     def error_check!
@@ -118,9 +131,5 @@ module MergeRequests
     def merge_request_info
       merge_request.to_reference(full: true)
     end
-
-    def source
-      @source ||= @merge_request.diff_head_sha
-    end
   end
 end

ee/app/services/merge_requests/squash_service.rb → app/services/merge_requests/squash_service.rb

-require 'securerandom'
-
 module MergeRequests
   class SquashService < MergeRequests::WorkingCopyBaseService
     def execute(merge_request)
@@ -10,14 +8,10 @@ module MergeRequests
     end
 
     def squash
-      if merge_request.commits_count <= 1
+      if merge_request.commits_count < 2
         return success(squash_sha: merge_request.diff_head_sha)
       end
 
-      unless project.feature_available?(:merge_request_squash)
-        return error('License does not allow squashing')
-      end
-
       if merge_request.squash_in_progress?
         return error('Squash task canceled: another squash is already in progress.')
       end

app/views/projects/merge_requests/show.html.haml

@@ -20,13 +20,12 @@
       window.gl = window.gl || {};
       window.gl.mrWidgetData = #{serialize_issuable(@merge_request, serializer: 'widget')}
 
+      window.gl.mrWidgetData.squash_before_merge_help_path = '#{help_page_path("user/project/merge_requests/squash_and_merge")}';
+
       // Append static, server-generated data not included in merge request entity (EE-Only)
       // Object.assign would be useful here, but it blows up Phantom.js in tests
       window.gl.mrWidgetData.is_geo_secondary_node = '#{Gitlab::Geo.secondary?}' === 'true';
       window.gl.mrWidgetData.geo_secondary_help_path = '#{help_page_path("/gitlab-geo/configuration.md")}';
-      window.gl.mrWidgetData.enable_squash_before_merge = '#{@merge_request.project.feature_available?(:merge_request_squash)}' === 'true';
-      window.gl.mrWidgetData.squash_before_merge_help_path = '#{help_page_path("user/project/merge_requests/squash_and_merge")}';
-
       window.gl.mrWidgetData.sast_help_path = '#{help_page_path("user/project/merge_requests/sast")}';
       window.gl.mrWidgetData.sast_container_help_path = '#{help_page_path("user/project/merge_requests/container_scanning")}';
       window.gl.mrWidgetData.dast_help_path = '#{help_page_path("user/project/merge_requests/dast")}';

app/views/shared/issuable/form/_merge_params.html.haml

@@ -12,4 +12,11 @@
           = check_box_tag 'merge_request[force_remove_source_branch]', '1', issuable.force_remove_source_branch?
           Remove source branch when merge request is accepted.
 
-= render 'shared/issuable/form/ee/squash_merge_param', issuable: issuable
+.form-group
+  .col-sm-10.col-sm-offset-2
+    .checkbox
+      = label_tag 'merge_request[squash]' do
+        = hidden_field_tag 'merge_request[squash]', '0', id: nil
+        = check_box_tag 'merge_request[squash]', '1', issuable.squash
+        Squash commits when merge request is accepted.
+        = link_to 'About this feature', help_page_path('user/project/merge_requests/squash_and_merge')

changelogs/unreleased/blackst0ne-squash-and-merge-in-gitlab-core-ce.yml

+---
+title: Add `Squash and merge` to GitLab Core (CE)
+merge_request: 18956
+author: "@blackst0ne"
+type: added

db/migrate/20180515005612_add_squash_to_merge_requests.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddSquashToMergeRequests < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+  disable_ddl_transaction!
+
+  DOWNTIME = false
+
+  def up
+    unless column_exists?(:merge_requests, :squash)
+      add_column_with_default :merge_requests, :squash, :boolean, default: false, allow_null: false
+    end
+  end
+
+  def down
+    remove_column :merge_requests, :squash if column_exists?(:merge_requests, :squash)
+  end
+end

db/schema.rb

@@ -1617,7 +1617,6 @@ ActiveRecord::Schema.define(version: 20180521171529) do
     t.text "title_html"
     t.text "description_html"
     t.integer "time_estimate"
-    t.boolean "squash", default: false, null: false
     t.integer "cached_markdown_version"
     t.datetime "last_edited_at"
     t.integer "last_edited_by_id"
@@ -1626,6 +1625,7 @@ ActiveRecord::Schema.define(version: 20180521171529) do
     t.boolean "discussion_locked"
     t.integer "latest_merge_request_diff_id"
     t.boolean "allow_maintainer_to_push"
+    t.boolean "squash", default: false, null: false
   end
 
   add_index "merge_requests", ["assignee_id"], name: "index_merge_requests_on_assignee_id", using: :btree

doc/api/merge_requests.md

@@ -107,6 +107,7 @@ Parameters:
     "changes_count": "1",
     "should_remove_source_branch": true,
     "force_remove_source_branch": false,
+    "squash": false,
     "web_url": "http://example.com/example/example/merge_requests/1",
     "time_stats": {
       "time_estimate": 0,
@@ -535,21 +536,20 @@ Creates a new merge request.
 POST /projects/:id/merge_requests
 ```
 
-| Attribute              | Type    | Required | Description                                                                     |
-| ---------              | ----    | -------- | -----------                                                                     |
-| `id`                   | integer/string  | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
-| `source_branch`        | string  | yes      | The source branch                                                               |
-| `target_branch`        | string  | yes      | The target branch                                                               |
-| `title`                | string  | yes      | Title of MR                                                                     |
-| `assignee_id`          | integer | no       | Assignee user ID                                                                |
-| `description`          | string  | no       | Description of MR                                                               |
-| `target_project_id`    | integer | no       | The target project (numeric id)                                                 |
-| `labels`               | string  | no       | Labels for MR as a comma-separated list                                         |
-| `milestone_id`         | integer | no       | The global ID of a milestone                                                           |
-| `remove_source_branch` | boolean | no       | Flag indicating if a merge request should remove the source branch when merging |
-| `approvals_before_merge` | integer| no | Number of approvals required before this can be merged (see below) |
-| `squash` | boolean| no | Squash commits into a single commit when merging |
-| `allow_maintainer_to_push` | boolean | no       | Whether or not a maintainer of the target project can push to the source branch  |
+| Attribute                  | Type    | Required | Description                                                                     |
+| ---------                  | ----    | -------- | -----------                                                                     |
+| `id`                       | integer/string  | yes      | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `source_branch`            | string  | yes      | The source branch                                                               |
+| `target_branch`            | string  | yes      | The target branch                                                               |
+| `title`                    | string  | yes      | Title of MR                                                                     |
+| `assignee_id`              | integer | no       | Assignee user ID                                                                |
+| `description`              | string  | no       | Description of MR                                                               |
+| `target_project_id`        | integer | no       | The target project (numeric id)                                                 |
+| `labels`                   | string  | no       | Labels for MR as a comma-separated list                                         |
+| `milestone_id`             | integer | no       | The ID of a milestone                                                           |
+| `remove_source_branch`     | boolean | no       | Flag indicating if a merge request should remove the source branch when merging |
+| `allow_maintainer_to_push` | boolean | no       | Whether or not a maintainer of the target project can push to the source branch |
+| `squash`                   | boolean | no       | Squash commits into a single commit when merging                                |
 
 If `approvals_before_merge` is not provided, it inherits the value from the
 target project. If it is provided, then the following conditions must hold in
@@ -634,21 +634,21 @@ Updates an existing merge request. You can change the target branch, title, or e
 PUT /projects/:id/merge_requests/:merge_request_iid
 ```
 
-| Attribute              | Type    | Required | Description                                                                     |
-| ---------              | ----    | -------- | -----------                                                                     |
-| `id`                   | integer/string | yes  | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
-| `merge_request_iid`    | integer | yes      | The ID of a merge request                                                       |
-| `target_branch`        | string  | no       | The target branch                                                               |
-| `title`                | string  | no       | Title of MR                                                                     |
-| `assignee_id`          | integer | no       | The ID of the user to assign the merge request to. Set to `0` or provide an empty value to unassign all assignees.  |
-| `milestone_id`         | integer | no       | The global ID of a milestone to assign the merge request to. Set to `0` or provide an empty value to unassign a milestone.|
-| `labels`               | string  | no       | Comma-separated label names for a merge request. Set to an empty string to unassign all labels.                    |
-| `description`          | string  | no       | Description of MR                                                               |
-| `state_event`          | string  | no       | New state (close/reopen)                                                        |
-| `remove_source_branch` | boolean | no       | Flag indicating if a merge request should remove the source branch when merging |
-| `squash` | boolean| no | Squash commits into a single commit when merging |
-| `discussion_locked`    | boolean | no       | Flag indicating if the merge request's discussion is locked. If the discussion is locked only project members can add, edit or resolve comments. |
-| `allow_maintainer_to_push` | boolean | no       | Whether or not a maintainer of the target project can push to the source branch  |
+| Attribute                  | Type    | Required | Description                                                                     |
+| ---------                  | ----    | -------- | -----------                                                                     |
+| `id`                       | integer/string | yes  | The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user |
+| `merge_request_iid`        | integer | yes      | The ID of a merge request                                                       |
+| `target_branch`            | string  | no       | The target branch                                                               |
+| `title`                    | string  | no       | Title of MR                                                                     |
+| `assignee_id`              | integer | no       | The ID of the user to assign the merge request to. Set to `0` or provide an empty value to unassign all assignees.  |
+| `milestone_id`             | integer | no       | The ID of a milestone to assign the merge request to. Set to `0` or provide an empty value to unassign a milestone.|
+| `labels`                   | string  | no       | Comma-separated label names for a merge request. Set to an empty string to unassign all labels.                    |
+| `description`              | string  | no       | Description of MR                                                               |
+| `state_event`              | string  | no       | New state (close/reopen)                                                        |
+| `remove_source_branch`     | boolean | no       | Flag indicating if a merge request should remove the source branch when merging |
+| `squash`                   | boolean | no       | Squash commits into a single commit when merging |
+| `discussion_locked`        | boolean | no       | Flag indicating if the merge request's discussion is locked. If the discussion is locked only project members can add, edit or resolve comments. |
+| `allow_maintainer_to_push` | boolean | no       | Whether or not a maintainer of the target project can push to the source branch |
 
 Must include at least one non-required attribute from above.
 
@@ -1227,7 +1227,7 @@ Example response:
     "changes_count": "1",
     "should_remove_source_branch": true,
     "force_remove_source_branch": false,
-    "squash": true,
+    "squash": false,
     "web_url": "http://example.com/example/example/merge_requests/1"
   },
   "target_url": "https://gitlab.example.com/gitlab-org/gitlab-ci/merge_requests/7",

doc/user/project/merge_requests/index.md

@@ -29,6 +29,7 @@ With GitLab merge requests, you can:
 - Enable [semi-linear history merge requests](#semi-linear-history-merge-requests) as another security layer to guarantee the pipeline is passing in the target branch
 - [Create new merge requests by email](#create-new-merge-requests-by-email)
 - Allow maintainers of the target project to push directly to the fork by [allowing edits from maintainers](maintainer_access.md)
+- [Squash and merge](squash_and_merge.md) for a cleaner commit history
 
 With **[GitLab Enterprise Edition][ee]**, you can also:
 

doc/user/project/merge_requests/squash_and_merge.md

-# Squash and merge **[STARTER]**
+# Squash and merge
 
-> [Introduced][ee-1024] in [GitLab Starter][ee] 8.17.
+> [Introduced][ee-1024] in [GitLab Starter][ee] 8.17, and in [GitLab CE][ce] [11.0][ce-18956].
 
 Combine all commits of your merge request into one and retain a clean history.
 
@@ -18,11 +18,11 @@ Into a single commit on merge:
 
 ![A squashed commit followed by a merge commit][squashed-commit]
 
-The squashed commit's commit message is the merge request title. And note that 
+The squashed commit's commit message is the merge request title. And note that
 the squashed commit is still followed by a merge commit, as the merge
 method for this example repository uses a merge commit. Squashing also works
 with the fast-forward merge strategy, see
-[squashing and fast-forward merge](#squashing-and-fast-forward-merge) for more
+[squashing and fast-forward merge](#squash-and-fast-forward-merge) for more
 details.
 
 ## Use cases
@@ -30,7 +30,7 @@ details.
 When working on a feature branch, you sometimes want to commit your current
 progress, but don't really care about the commit messages. Those 'work in
 progress commits' don't necessarily contain important information and as such
-you'd rather not include them in your target branch. 
+you'd rather not include them in your target branch.
 
 With squash and merge, when the merge request is ready to be merged,
 all you have to do is enable squashing before you press merge to join
@@ -69,10 +69,12 @@ so a merge request may need to be rebased before squashing, even though
 squashing can itself be considered equivalent to rebasing.
 
 [ee-1024]: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1024
+[ce-18956]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18956
 [mr-commits]: img/squash_mr_commits.png
 [squashed-commit]: img/squash_squashed_commit.png
 [squash-edit-form]: img/squash_edit_form.png
 [squash-mr-widget]: img/squash_mr_widget.png
 [ff-merge]: fast_forward_merge.md#enabling-fast-forward-merges
+[ce]: https://about.gitlab.com/products/
 [ee]: https://about.gitlab.com/products/
 [revert]: revert_changes.md

ee/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_ready_to_merge.vue

-<script>
-import eventHub from '~/vue_merge_request_widget/event_hub';
-import ReadyToMergeState from '~/vue_merge_request_widget/components/states/ready_to_merge.vue';
-import SquashBeforeMerge from './mr_widget_squash_before_merge.vue';
-
-export default {
-  name: 'ReadyToMerge',
-  components: {
-    SquashBeforeMerge,
-  },
-  extends: ReadyToMergeState,
-  data() {
-    return {
-      additionalParams: {
-        squash: this.mr.squash,
-      },
-    };
-  },
-  created() {
-    eventHub.$on('MRWidgetUpdateSquash', val => {
-      this.additionalParams.squash = val;
-    });
-  },
-  methods: {
-    // called in CE super component before form submission
-    setAdditionalParams(options) {
-      if (this.additionalParams) {
-        Object.assign(options, this.additionalParams);
-      }
-    },
-  },
-};
-</script>

ee/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue

-<script>
-import eventHub from '~/vue_merge_request_widget/event_hub';
-import CESquashBeforeMerge from '~/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue';
-
-export default {
-  extends: CESquashBeforeMerge,
-  props: {
-    mr: {
-      type: Object,
-      required: true,
-    },
-    isMergeButtonDisabled: {
-      type: Boolean,
-      required: true,
-    },
-  },
-  data() {
-    return {
-      squashBeforeMerge: this.mr.squash,
-    };
-  },
-  methods: {
-    updateSquashModel() {
-      eventHub.$emit('MRWidgetUpdateSquash', this.squashBeforeMerge);
-    },
-  },
-};
-</script>
-
-<template>
-  <div class="accept-control inline">
-    <label class="merge-param-checkbox">
-      <input
-        type="checkbox"
-        name="squash"
-        class="qa-squash-checkbox"
-        :disabled="isMergeButtonDisabled"
-        v-model="squashBeforeMerge"
-        @change="updateSquashModel"
-      />
-      Squash commits
-    </label>
-    <a
-      :href="mr.squashBeforeMergeHelpPath"
-      data-title="About this feature"
-      data-toggle="tooltip"
-      data-placement="bottom"
-      target="_blank"
-      rel="noopener noreferrer nofollow"
-      data-container="body"
-    >
-      <i
-        class="fa fa-question-circle"
-        aria-hidden="true"
-      >
-      </i>
-    </a>
-  </div>
-</template>

ee/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js

@@ -26,18 +26,11 @@ export default class MergeRequestStore extends CEMergeRequestStore {
 
   setData(data) {
     this.initGeo(data);
-    this.initSquashBeforeMerge(data);
     this.initApprovals(data);
 
     super.setData(data);
   }
 
-  initSquashBeforeMerge(data) {
-    this.squashBeforeMergeHelpPath =
-      this.squashBeforeMergeHelpPath || data.squash_before_merge_help_path;
-    this.enableSquashBeforeMerge = this.enableSquashBeforeMerge || data.enable_squash_before_merge;
-  }
-
   initGeo(data) {
     this.isGeoSecondaryNode = this.isGeoSecondaryNode || data.is_geo_secondary_node;
     this.geoSecondaryHelpPath = this.geoSecondaryHelpPath || data.geo_secondary_help_path;

ee/app/controllers/ee/projects/merge_requests/application_controller.rb

@@ -25,7 +25,6 @@ module EE
             :approver_group_ids,
             :approver_ids
           )
-          attrs << :squash if project.feature_available?(:merge_request_squash)
 
           attrs
         end

ee/app/controllers/ee/projects/merge_requests_controller.rb

@@ -64,13 +64,6 @@ module EE
           end
         end
       end
-
-      def merge_params_attributes
-        attrs = super
-        attrs << :squash if project.feature_available?(:merge_request_squash)
-
-        attrs
-      end
     end
   end
 end

ee/app/models/ee/merge_request.rb

@@ -48,18 +48,6 @@ module EE
       delegate :expose_dast_data?, to: :head_pipeline, allow_nil: true
     end
 
-    def squash_in_progress?
-      # The source project can be deleted
-      return false unless source_project
-
-      source_project.repository.squash_in_progress?(id)
-    end
-
-    def squash
-      super && project.feature_available?(:merge_request_squash)
-    end
-    alias_method :squash?, :squash
-
     def supports_weight?
       false
     end

ee/app/models/ee/repository.rb

@@ -25,13 +25,5 @@ module EE
       expire_branch_cache if exists?
       expire_content_cache
     end
-
-    def squash(user, merge_request)
-      raw.squash(user, merge_request.id, branch: merge_request.target_branch,
-                                         start_sha: merge_request.diff_start_sha,
-                                         end_sha: merge_request.diff_head_sha,
-                                         author: merge_request.author,
-                                         message: merge_request.title)
-    end
   end
 end

ee/app/models/license.rb

@@ -21,7 +21,6 @@ class License < ActiveRecord::Base
     ldap_group_sync
     member_lock
     merge_request_approvers
-    merge_request_squash
     multiple_ldap_servers
     multiple_issue_assignees
     multiple_project_issue_boards
@@ -94,7 +93,6 @@ class License < ActiveRecord::Base
     issue_weights
     jenkins_integration
     merge_request_approvers
-    merge_request_squash
     multiple_issue_assignees
     multiple_project_issue_boards
     multiple_group_issue_boards

ee/app/services/ee/merge_requests/merge_service.rb

@@ -10,19 +10,6 @@ module EE
         super
       end
 
-      def source
-        return merge_request.diff_head_sha unless merge_request.squash
-
-        squash_result = ::MergeRequests::SquashService.new(project, current_user, params).execute(merge_request)
-
-        case squash_result[:status]
-        when :success
-          squash_result[:squash_sha]
-        when :error
-          raise ::MergeRequests::MergeService::MergeError, squash_result[:message]
-        end
-      end
-
       def hooks_validation_pass?(merge_request)
         # handle_merge_error needs this. We should move that to a separate
         # object instead of relying on the order of method calls.

ee/app/views/shared/issuable/form/ee/_squash_merge_param.html.haml

-- issuable = local_assigns.fetch(:issuable)
-
-- if issuable.project.feature_available?(:merge_request_squash)
-  .form-group.row
-    .col-sm-10.offset-sm-2
-      = label_tag 'merge_request[squash]' do
-        = hidden_field_tag 'merge_request[squash]', '0', id: nil
-        = check_box_tag 'merge_request[squash]', '1', issuable.squash
-        Squash commits when merge request is accepted.
-        = link_to 'About this feature', help_page_path('user/project/merge_requests/squash_and_merge')
-- elsif show_promotions? && show_callout?('promote_squash_commits_dismissed')
-  .form-group.row
-    .col-sm-10.offset-sm-2
-      = render 'shared/promotions/promote_squash_commits'

ee/app/views/shared/promotions/_promote_squash_commits.html.haml

-.user-callout.promotion-callout.prepend-top-10#promote_squash_commits{ data: { uid: 'promote_squash_commits_dismissed' } }
-  .bordered-box.content-block
-    %button.btn.btn-default.close.js-close-callout{ type: 'button', 'aria-label' => 'Dismiss merge request promotion' }
-      = icon('times', class: 'dismiss-icon', 'aria-hidden' => 'true')
-    .user-callout-copy
-      %h4
-        - if Gitlab::CurrentSettings.should_check_namespace_plan?
-          Upgrade your plan to improve Merge Requests with Squash Commit.
-        - else
-          Improve Merge Requests with Squash Commit and GitLab Enterprise Edition.
-      %p
-        Squashing lets you tidy up the commit history of a branch when accepting a merge request. It applies all of the changes in the merge request as a single commit, and then merges that commit using the merge method set for the project.
-        = link_to 'Read more', help_page_path('user/project/merge_requests/squash_and_merge.html'), target: '_blank'
-
-      = render 'shared/promotions/promotion_link_project'

ee/db/migrate/20161230123835_add_squash_to_merge_requests.rb → ee/db/migrate/20161230123835_add_squash_to_merge_requests_ee.rb

 # rubocop:disable Migration/AddColumnWithDefaultToLargeTable
 # rubocop:disable Migration/UpdateLargeTable
-class AddSquashToMergeRequests < ActiveRecord::Migration
+class AddSquashToMergeRequestsEE < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
   disable_ddl_transaction!
 
   DOWNTIME = false
 
   def up
-    add_column_with_default :merge_requests, :squash, :boolean, default: false, allow_null: false
+    unless column_exists?(:merge_requests, :squash)
+      add_column_with_default :merge_requests, :squash, :boolean, default: false, allow_null: false
+    end
   end
 
   def down
-    remove_column :merge_requests, :squash
+    remove_column :merge_requests, :squash if column_exists?(:merge_requests, :squash)
   end
 end

ee/lib/ee/api/entities.rb

@@ -62,7 +62,6 @@ module EE
 
         prepended do
           expose :approvals_before_merge
-          expose :squash, if: ->(mr, _) { mr.project.feature_available?(:merge_request_squash) }
         end
       end
 

ee/lib/ee/api/merge_requests.rb

@@ -3,29 +3,10 @@ module EE
     module MergeRequests
       extend ActiveSupport::Concern
 
-      class_methods do
-        def update_params_at_least_one_of
-          super.push(*%i[
-            squash
-          ])
-        end
-      end
-
       prepended do
         helpers do
-          params :merge_params_ee do
-            optional :squash, type: Grape::API::Boolean, desc: 'When true, the commits will be squashed into a single commit on merge'
-          end
-
           params :optional_params_ee do
             optional :approvals_before_merge, type: Integer, desc: 'Number of approvals required before this can be merged'
-            use :merge_params_ee
-          end
-
-          def update_merge_request_ee(merge_request)
-            if params[:squash] && merge_request.project.feature_available?(:merge_request_squash)
-              merge_request.update(squash: params[:squash])
-            end
           end
         end
 

ee/spec/controllers/projects/merge_requests_controller_spec.rb

@@ -315,49 +315,6 @@ describe Projects::MergeRequestsController do
     end
   end
 
-  describe 'POST merge' do
-    let(:base_params) do
-      {
-        namespace_id: project.namespace,
-        project_id: project,
-        id: merge_request.iid,
-        squash: false,
-        format: 'json'
-      }
-    end
-
-    context 'when the sha parameter matches the source SHA' do
-      def merge_with_sha(params = {})
-        post :merge, base_params.merge(sha: merge_request.diff_head_sha).merge(params)
-      end
-
-      context 'when squash is passed as 1' do
-        it 'updates the squash attribute on the MR to true' do
-          merge_request.update(squash: false)
-          merge_with_sha(squash: '1')
-
-          expect(merge_request.reload.squash).to be_truthy
-        end
-
-        it 'merges even when squash is unavailable' do
-          stub_licensed_features(merge_request_squash: false)
-          merge_with_sha(squash: '1')
-
-          expect(merge_request.reload.squash).to be_falsey
-        end
-      end
-
-      context 'when squash is passed as 0' do
-        it 'updates the squash attribute on the MR to false' do
-          merge_request.update(squash: true)
-          merge_with_sha(squash: '0')
-
-          expect(merge_request.reload.squash).to be_falsey
-        end
-      end
-    end
-  end
-
   describe 'POST #rebase' do
     def post_rebase
       post :rebase, namespace_id: project.namespace, project_id: project, id: merge_request

ee/spec/features/promotion_spec.rb

@@ -161,34 +161,6 @@ describe 'Promotions', :js do
     end
   end
 
-  describe 'for squash commits', :js do
-    before do
-      allow(License).to receive(:current).and_return(nil)
-      stub_application_setting(check_namespace_plan: false)
-
-      project.add_master(user)
-      sign_in(user)
-    end
-
-    it 'should appear in new MR page' do
-      visit project_new_merge_request_path(project, merge_request: { target_branch: 'master', source_branch: 'feature' })
-
-      expect(find('#promote_squash_commits')).to have_content 'Improve Merge Requests with Squash Commit and GitLab Enterprise Edition.'
-    end
-
-    it 'does not show when cookie is set' do
-      visit project_new_merge_request_path(project, merge_request: { target_branch: 'master', source_branch: 'feature' })
-
-      within('#promote_squash_commits') do
-        find('.close').click
-      end
-
-      visit project_new_merge_request_path(project, merge_request: { target_branch: 'master', source_branch: 'feature' })
-
-      expect(page).not_to have_selector('#promote_squash_commits')
-    end
-  end
-
   describe 'for burndown charts', :js do
     before do
       stub_application_setting(check_namespace_plan: true)

ee/spec/models/merge_request_spec.rb

@@ -14,85 +14,6 @@ describe MergeRequest do
     it { is_expected.to have_many(:approved_by_users) }
   end
 
-  describe '#squash_in_progress?' do
-    shared_examples 'checking whether a squash is in progress' do
-      let(:repo_path) { subject.source_project.repository.path }
-      let(:squash_path) { File.join(repo_path, "gitlab-worktree", "squash-#{subject.id}") }
-
-      before do
-        system(*%W(#{Gitlab.config.git.bin_path} -C #{repo_path} worktree add --detach #{squash_path} master))
-      end
-
-      it 'returns true when there is a current squash directory' do
-        expect(subject.squash_in_progress?).to be_truthy
-      end
-
-      it 'returns false when there is no squash directory' do
-        FileUtils.rm_rf(squash_path)
-
-        expect(subject.squash_in_progress?).to be_falsey
-      end
-
-      it 'returns false when the squash directory has expired' do
-        time = 20.minutes.ago.to_time
-        File.utime(time, time, squash_path)
-
-        expect(subject.squash_in_progress?).to be_falsey
-      end
-
-      it 'returns false when the source project has been removed' do
-        allow(subject).to receive(:source_project).and_return(nil)
-
-        expect(subject.squash_in_progress?).to be_falsey
-      end
-    end
-
-    context 'when Gitaly squash_in_progress is enabled' do
-      it_behaves_like 'checking whether a squash is in progress'
-    end
-
-    context 'when Gitaly squash_in_progress is disabled', :disable_gitaly do
-      it_behaves_like 'checking whether a squash is in progress'
-    end
-  end
-
-  describe '#squash?' do
-    let(:merge_request) { build(:merge_request, squash: squash) }
-    subject { merge_request.squash? }
-
-    context 'unlicensed' do
-      before do
-        stub_licensed_features(merge_request_squash: false)
-      end
-
-      context 'disabled in database' do
-        let(:squash) { false }
-
-        it { is_expected.to be_falsy }
-      end
-
-      context 'enabled in database' do
-        let(:squash) { true }
-
-        it { is_expected.to be_falsy }
-      end
-    end
-
-    context 'licensed' do
-      context 'disabled in database' do
-        let(:squash) { false }
-
-        it { is_expected.to be_falsy }
-      end
-
-      context 'licensed' do
-        let(:squash) { true }
-
-        it { is_expected.to be_truthy }
-      end
-    end
-  end
-
   describe '#approvals_before_merge' do
     where(:license_value, :db_value, :expected) do
       true  | 5   | 5

ee/spec/services/merge_requests/squash_service_spec.rb

-require 'spec_helper'
-
-describe MergeRequests::SquashService do
-  let(:service) { described_class.new(project, user, {}) }
-  let(:user) { project.owner }
-  let(:project) { create(:project, :repository) }
-  let(:repository) { project.repository.raw }
-  let(:log_error) { "Failed to squash merge request #{merge_request.to_reference(full: true)}:" }
-  let(:squash_dir_path) do
-    File.join(Gitlab.config.shared.path, 'tmp/squash', repository.gl_repository, merge_request.id.to_s)
-  end
-  let(:merge_request_with_one_commit) do
-    create(:merge_request,
-           source_branch: 'feature', source_project: project,
-           target_branch: 'master', target_project: project)
-  end
-
-  let(:merge_request_with_only_new_files) do
-    create(:merge_request,
-           source_branch: 'video', source_project: project,
-           target_branch: 'master', target_project: project)
-  end
-
-  let(:merge_request_with_large_files) do
-    create(:merge_request,
-           source_branch: 'squash-large-files', source_project: project,
-           target_branch: 'master', target_project: project)
-  end
-
-  shared_examples 'the squash succeeds' do
-    it 'returns the squashed commit SHA' do
-      result = service.execute(merge_request)
-
-      expect(result).to match(status: :success, squash_sha: a_string_matching(/\h{40}/))
-      expect(result[:squash_sha]).not_to eq(merge_request.diff_head_sha)
-    end
-
-    it 'cleans up the temporary directory' do
-      service.execute(merge_request)
-
-      expect(File.exist?(squash_dir_path)).to be(false)
-    end
-
-    it 'does not keep the branch push event' do
-      expect { service.execute(merge_request) }.not_to change { Event.count }
-    end
-
-    context 'the squashed commit' do
-      let(:squash_sha) { service.execute(merge_request)[:squash_sha] }
-      let(:squash_commit) { project.repository.commit(squash_sha) }
-
-      it 'copies the author info and message from the merge request' do
-        expect(squash_commit.author_name).to eq(merge_request.author.name)
-        expect(squash_commit.author_email).to eq(merge_request.author.email)
-
-        # Commit messages have a trailing newline, but titles don't.
-        expect(squash_commit.message.chomp).to eq(merge_request.title)
-      end
-
-      it 'sets the current user as the committer' do
-        expect(squash_commit.committer_name).to eq(user.name.chomp('.'))
-        expect(squash_commit.committer_email).to eq(user.email)
-      end
-
-      it 'has the same diff as the merge request, but a different SHA' do
-        rugged = project.repository.rugged
-        mr_diff = rugged.diff(merge_request.diff_base_sha, merge_request.diff_head_sha)
-        squash_diff = rugged.diff(merge_request.diff_start_sha, squash_sha)
-
-        expect(squash_diff.patch.length).to eq(mr_diff.patch.length)
-        expect(squash_commit.sha).not_to eq(merge_request.diff_head_sha)
-      end
-    end
-  end
-
-  describe '#execute' do
-    context 'when there is only one commit in the merge request' do
-      it 'returns that commit SHA' do
-        result = service.execute(merge_request_with_one_commit)
-
-        expect(result).to match(status: :success, squash_sha: merge_request_with_one_commit.diff_head_sha)
-      end
-
-      it 'does not perform any git actions' do
-        expect(repository).not_to receive(:popen)
-
-        service.execute(merge_request_with_one_commit)
-      end
-    end
-
-    context 'when squashing only new files' do
-      let(:merge_request) { merge_request_with_only_new_files }
-
-      include_examples 'the squash succeeds'
-    end
-
-    context 'when squashing with files too large to display' do
-      let(:merge_request) { merge_request_with_large_files }
-
-      include_examples 'the squash succeeds'
-    end
-
-    context 'squashing is unlicensed' do
-      before do
-        stub_licensed_features(merge_request_squash: false)
-      end
-
-      subject { service.execute(merge_request_with_only_new_files) }
-
-      it { is_expected.to match(status: :error, message: a_string_including('License')) }
-    end
-
-    context 'git errors' do
-      let(:merge_request) { merge_request_with_only_new_files }
-      let(:error) { 'A test error' }
-
-      context 'with gitaly enabled' do
-        before do
-          allow(repository.gitaly_operation_client).to receive(:user_squash)
-            .and_raise(Gitlab::Git::Repository::GitError, error)
-        end
-
-        it 'logs the stage and output' do
-          expect(service).to receive(:log_error).with(log_error)
-          expect(service).to receive(:log_error).with(error)
-
-          service.execute(merge_request)
-        end
-
-        it 'returns an error' do
-          expect(service.execute(merge_request)).to match(status: :error,
-                                                          message: a_string_including('squash'))
-        end
-      end
-
-      context 'with Gitaly disabled', :skip_gitaly_mock do
-        stages = {
-          'add worktree for squash' => 'worktree',
-          'configure sparse checkout' => 'config',
-          'get files in diff' => 'diff --name-only',
-          'check out target branch' => 'checkout',
-          'apply patch' => 'diff --binary',
-          'commit squashed changes' => 'commit',
-          'get SHA of squashed commit' => 'rev-parse'
-        }
-
-        stages.each do |stage, command|
-          context "when the #{stage} stage fails" do
-            before do
-              git_command = a_collection_containing_exactly(
-                a_string_starting_with("#{Gitlab.config.git.bin_path} #{command}")
-              ).or(
-                a_collection_starting_with([Gitlab.config.git.bin_path] + command.split)
-              )
-
-              allow(repository).to receive(:popen).and_return(['', 0])
-              allow(repository).to receive(:popen).with(git_command, anything, anything, anything).and_return([error, 1])
-            end
-
-            it 'logs the stage and output' do
-              expect(service).to receive(:log_error).with(log_error)
-              expect(service).to receive(:log_error).with(error)
-
-              service.execute(merge_request)
-            end
-
-            it 'returns an error' do
-              expect(service.execute(merge_request)).to match(status: :error,
-                                                              message: a_string_including('squash'))
-            end
-
-            it 'cleans up the temporary directory' do
-              expect(File.exist?(squash_dir_path)).to be(false)
-
-              service.execute(merge_request)
-            end
-          end
-        end
-      end
-    end
-
-    context 'when any other exception is thrown' do
-      let(:merge_request) { merge_request_with_only_new_files }
-      let(:error) { 'A test error' }
-
-      before do
-        allow(merge_request).to receive(:commits_count).and_raise(error)
-      end
-
-      it 'logs the MR reference and exception' do
-        expect(service).to receive(:log_error).with(a_string_including("#{project.full_path}#{merge_request.to_reference}"))
-        expect(service).to receive(:log_error).with(error)
-
-        service.execute(merge_request)
-      end
-
-      it 'returns an error' do
-        expect(service.execute(merge_request)).to match(status: :error,
-                                                        message: a_string_including('squash'))
-      end
-
-      it 'cleans up the temporary directory' do
-        service.execute(merge_request)
-
-        expect(File.exist?(squash_dir_path)).to be(false)
-      end
-    end
-  end
-end

lib/api/entities.rb

@@ -570,6 +570,8 @@ module API
       expose :time_stats, using: 'API::Entities::IssuableTimeStats' do |merge_request|
         merge_request
       end
+
+      expose :squash
     end
 
     class MergeRequest < MergeRequestBasic

lib/api/merge_requests.rb

@@ -10,12 +10,6 @@ module API
     helpers do
       params :optional_params_ee do
       end
-
-      params :merge_params_ee do
-      end
-
-      def update_merge_request_ee(merge_request)
-      end
     end
 
     def self.update_params_at_least_one_of
@@ -29,6 +23,7 @@ module API
         target_branch
         title
         discussion_locked
+        squash
       ]
     end
 
@@ -148,6 +143,7 @@ module API
           optional :labels, type: String, desc: 'Comma-separated list of label names'
           optional :remove_source_branch, type: Boolean, desc: 'Remove source branch when merging'
           optional :allow_maintainer_to_push, type: Boolean, desc: 'Whether a maintainer of the target project can push to the source project'
+          optional :squash, type: Grape::API::Boolean, desc: 'When true, the commits will be squashed into a single commit on merge'
 
           use :optional_params_ee
         end
@@ -310,8 +306,7 @@ module API
         optional :merge_when_pipeline_succeeds, type: Boolean,
                                                 desc: 'When true, this merge request will be merged when the pipeline succeeds'
         optional :sha, type: String, desc: 'When present, must have the HEAD SHA of the source branch'
-
-        use :merge_params_ee
+        optional :squash, type: Grape::API::Boolean, desc: 'When true, the commits will be squashed into a single commit on merge'
       end
       put ':id/merge_requests/:merge_request_iid/merge' do
         Gitlab::QueryLimiting.whitelist('https://gitlab.com/gitlab-org/gitlab-ce/issues/42317')
@@ -329,7 +324,7 @@ module API
 
         check_sha_param!(params, merge_request)
 
-        update_merge_request_ee(merge_request)
+        merge_request.update(squash: params[:squash]) if params[:squash]
 
         merge_params = {
           commit_message: params[:merge_commit_message],

lib/api/v3/entities.rb

@@ -139,7 +139,7 @@ module API
         expose :should_remove_source_branch?, as: :should_remove_source_branch
         expose :force_remove_source_branch?, as: :force_remove_source_branch
 
-        expose :squash, if: ->(mr, _) { mr.project.feature_available?(:merge_request_squash) }
+        expose :squash
 
         expose :web_url do |merge_request, options|
           Gitlab::UrlBuilder.build(merge_request)

lib/api/v3/merge_requests.rb

@@ -216,9 +216,7 @@ module API
               render_api_error!("SHA does not match HEAD of source branch: #{merge_request.diff_head_sha}", 409)
             end
 
-            if params[:squash] && merge_request.project.feature_available?(:merge_request_squash)
-              merge_request.update(squash: params[:squash])
-            end
+            merge_request.update(squash: params[:squash]) if params[:squash]
 
             merge_params = {
               commit_message: params[:merge_commit_message],

qa/qa/ee/page/merge_request/show.rb

@@ -8,19 +8,7 @@ module QA
               view 'app/assets/javascripts/vue_merge_request_widget/components/states/sha_mismatch.vue' do
                 element :head_mismatch, "The source branch HEAD has recently changed."
               end
-
-              view 'ee/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue' do
-                element :squash_checkbox
-              end
-            end
-          end
-
-          def mark_to_squash
-            wait(reload: true) do
-              has_css?(element_selector_css(:squash_checkbox))
             end
-
-            click_element :squash_checkbox
           end
         end
       end

qa/qa/page/merge_request/show.rb

@@ -18,6 +18,10 @@ module QA
           element :no_fast_forward_message, 'Fast-forward merge is not possible'
         end
 
+        view 'app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_squash_before_merge.vue' do
+          element :squash_checkbox
+        end
+
         def rebase!
           click_element :mr_rebase_button
 
@@ -43,6 +47,14 @@ module QA
             has_text?('The changes were merged into')
           end
         end
+
+        def mark_to_squash
+          wait(reload: true) do
+            has_css?(element_selector_css(:squash_checkbox))
+          end
+
+          click_element :squash_checkbox
+        end
       end
     end
   end

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -316,8 +316,8 @@ describe Projects::MergeRequestsController do
     end
 
     context 'when the sha parameter matches the source SHA' do
-      def merge_with_sha
-        post :merge, base_params.merge(sha: merge_request.diff_head_sha)
+      def merge_with_sha(params = {})
+        post :merge, base_params.merge(sha: merge_request.diff_head_sha).merge(params)
       end
 
       it 'returns :success' do
@@ -332,6 +332,24 @@ describe Projects::MergeRequestsController do
         merge_with_sha
       end
 
+      context 'when squash is passed as 1' do
+        it 'updates the squash attribute on the MR to true' do
+          merge_request.update(squash: false)
+          merge_with_sha(squash: '1')
+
+          expect(merge_request.reload.squash).to be_truthy
+        end
+      end
+
+      context 'when squash is passed as 0' do
+        it 'updates the squash attribute on the MR to false' do
+          merge_request.update(squash: true)
+          merge_with_sha(squash: '0')
+
+          expect(merge_request.reload.squash).to be_falsey
+        end
+      end
+
       context 'when the pipeline succeeds is passed' do
         let!(:head_pipeline) do
           create(:ci_empty_pipeline, project: project, sha: merge_request.diff_head_sha, ref: merge_request.source_branch, head_pipeline_of: merge_request)

ee/spec/features/merge_requests/squash_spec.rb → spec/features/merge_requests/user_squashes_merge_request_spec.rb

 require 'spec_helper'
 
-feature 'Squashing merge requests', :js do
+feature 'User squashes a merge request', :js do
   let(:user) { create(:user) }
   let(:project) { create(:project, :repository) }
   let(:source_branch) { 'csv' }
@@ -121,24 +121,4 @@ feature 'Squashing merge requests', :js do
       include_examples 'no squash'
     end
   end
-
-  context 'squash is unlicensed' do
-    let(:merge_request) { create(:merge_request, source_project: project, target_project: project, source_branch: source_branch, target_branch: 'master', squash: true) }
-
-    before do
-      stub_licensed_features(merge_request_squash: false)
-    end
-
-    it 'does not show squash option when creating MR' do
-      visit project_new_merge_request_path(project, merge_request: { target_branch: 'master', source_branch: source_branch })
-
-      expect(page).to have_no_field('merge_request[squash]')
-    end
-
-    it 'does not show squash option when viewing MR' do
-      visit project_merge_request_path(project, merge_request)
-
-      expect(page).to have_no_field('squash')
-    end
-  end
 end

spec/fixtures/api/schemas/entities/merge_request_widget.json

@@ -114,10 +114,10 @@
     "rebase_in_progress": { "type": "boolean" },
     "can_push_to_source_branch": { "type": "boolean" },
     "rebase_path": { "type": ["string", "null"] },
+    "squash": { "type": "boolean" },
 
     // EE-specific
     "approvals_before_merge": { "type": ["integer", "null"] },
-    "squash": { "type": "boolean" },
     "approved": { "type": "boolean" },
     "approvals_path": { "type": ["string", "null"] },
     "codeclimate": {

spec/models/merge_request_spec.rb

@@ -14,6 +14,65 @@ describe MergeRequest do
     it { is_expected.to have_many(:merge_request_diffs) }
   end
 
+  describe '#squash_in_progress?' do
+    shared_examples 'checking whether a squash is in progress' do
+      let(:repo_path) { subject.source_project.repository.path }
+      let(:squash_path) { File.join(repo_path, "gitlab-worktree", "squash-#{subject.id}") }
+
+      before do
+        system(*%W(#{Gitlab.config.git.bin_path} -C #{repo_path} worktree add --detach #{squash_path} master))
+      end
+
+      it 'returns true when there is a current squash directory' do
+        expect(subject.squash_in_progress?).to be_truthy
+      end
+
+      it 'returns false when there is no squash directory' do
+        FileUtils.rm_rf(squash_path)
+
+        expect(subject.squash_in_progress?).to be_falsey
+      end
+
+      it 'returns false when the squash directory has expired' do
+        time = 20.minutes.ago.to_time
+        File.utime(time, time, squash_path)
+
+        expect(subject.squash_in_progress?).to be_falsey
+      end
+
+      it 'returns false when the source project has been removed' do
+        allow(subject).to receive(:source_project).and_return(nil)
+
+        expect(subject.squash_in_progress?).to be_falsey
+      end
+    end
+
+    context 'when Gitaly squash_in_progress is enabled' do
+      it_behaves_like 'checking whether a squash is in progress'
+    end
+
+    context 'when Gitaly squash_in_progress is disabled', :disable_gitaly do
+      it_behaves_like 'checking whether a squash is in progress'
+    end
+  end
+
+  describe '#squash?' do
+    let(:merge_request) { build(:merge_request, squash: squash) }
+    subject { merge_request.squash? }
+
+    context 'disabled in database' do
+      let(:squash) { false }
+
+      it { is_expected.to be_falsy }
+    end
+
+    context 'enabled in database' do
+      let(:squash) { true }
+
+      it { is_expected.to be_truthy }
+    end
+  end
+
   describe 'modules' do
     subject { described_class }