Add squash option to MR UI

app/assets/stylesheets/pages/merge_requests.scss

@@ -62,7 +62,7 @@
         }
       }
 
-      .remove_source_checkbox {
+      .merge-param-checkbox {
         margin: 0;
       }
     }

app/controllers/projects/merge_requests_controller.rb

@@ -338,7 +338,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       return
     end
 
-    @merge_request.update(merge_error: nil)
+    @merge_request.update(merge_error: nil, squash: merge_params[:squash])
 
     if params[:merge_when_build_succeeds].present?
       unless @merge_request.head_pipeline
@@ -699,6 +699,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       approvals_before_merge
       approver_group_ids
       approver_ids
+      squash
     ]
   end
 
@@ -716,7 +717,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def merge_params
-    params.permit(:should_remove_source_branch, :commit_message)
+    params.permit(:should_remove_source_branch, :commit_message, :squash)
   end
 
   # Make sure merge requests created before 8.0

app/views/projects/merge_requests/widget/open/_accept.html.haml

@@ -35,9 +35,14 @@
           The source branch will be removed.
       - elsif @merge_request.can_remove_source_branch?(current_user)
         .accept-control.checkbox
-          = label_tag :should_remove_source_branch, class: "remove_source_checkbox" do
+          = label_tag :should_remove_source_branch, class: "merge-param-checkbox" do
             = check_box_tag :should_remove_source_branch
             Remove source branch
+      .accept-control.checkbox
+        = label_tag :squash, class: 'merge-param-checkbox' do
+          = hidden_field_tag :squash, '0', id: nil
+          = check_box_tag :squash, '1', @merge_request.squash
+          Squash commits
 
       .accept-control.right
         - if @project.merge_requests_ff_only_enabled

app/views/projects/merge_requests/widget/open/_merge_when_build_succeeds.html.haml

@@ -7,10 +7,12 @@
 %div
   %p
     = succeed '.' do
+      The changes will be
+      - if @merge_request.squash
+        squashed and
       - if @project.merge_requests_ff_only_enabled
-        The changes will be fast-forward merged into
-      - else
-        The changes will be merged into
+        fast-forward
+      merged into
       %span.label-branch= @merge_request.target_branch
     - if @merge_request.remove_source_branch?
       The source branch will be removed.

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

@@ -28,3 +28,12 @@
           = hidden_field_tag 'merge_request[force_remove_source_branch]', '0', id: nil
           = check_box_tag 'merge_request[force_remove_source_branch]', '1', issuable.force_remove_source_branch?
           Remove source branch when merge request is accepted.
+
+- if issuable.new_record?
+  .form-group
+    .col-sm-10.col-sm-offset-2
+      .checkbox
+        = label_tag 'merge_request[squash]' do
+          = check_box_tag 'merge_request[squash]', nil
+          Squash commits on merge. The commit message for the last commit will
+          be used.

db/migrate/20161230123835_add_squash_to_merge_requests.rb

+class AddSquashToMergeRequests < 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
+  end
+
+  def down
+    remove_column :merge_requests, :squash
+  end
+end

db/schema.rb

@@ -782,6 +782,7 @@ ActiveRecord::Schema.define(version: 20170121130655) do
     t.text "title_html"
     t.text "description_html"
     t.integer "time_estimate"
+    t.boolean "squash", default: false, null: false
   end
 
   add_index "merge_requests", ["assignee_id"], name: "index_merge_requests_on_assignee_id", using: :btree

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -492,6 +492,7 @@ describe Projects::MergeRequestsController do
         namespace_id: project.namespace.path,
         project_id: project.path,
         id: merge_request.iid,
+        squash: false,
         format: 'raw'
       }
     end
@@ -529,8 +530,26 @@ 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
+
+      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 1' 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
 
       it 'returns :success' do

spec/lib/gitlab/import_export/safe_model_attributes.yml

@@ -154,6 +154,7 @@ MergeRequest:
 - approvals_before_merge
 - rebase_commit_sha
 - time_estimate
+- squash
 MergeRequestDiff:
 - id
 - state