Backport changes from EE squashsquash

Backport changes from the EE-only squash implementation, which would
otherwise conflict when merge CE into EE.

<https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1024>

13 files changed, 75 insertions, 28 deletions

diff --git a/app/assets/stylesheets/pages/merge_requests.scss b/app/assets/stylesheets/pages/merge_requests.scss
index ab68b360f93..0c013915a63 100644
--- a/app/assets/stylesheets/pages/merge_requests.scss
+++ b/app/assets/stylesheets/pages/merge_requests.scss
@@ -56,15 +56,24 @@
       &.right {
         float: right;
         padding-right: 0;
+      }
 
-        a {
-          color: $gl-text-color;
-        }
+      .modify-merge-commit-link {
+        color: $gl-text-color;
       }
 
-      .remove_source_checkbox {
+      .merge-param-checkbox {
         margin: 0;
       }
+
+      a .fa-question-circle {
+        color: $gl-text-color-secondary;
+
+        &:hover,
+        &:focus {
+          color: $link-hover-color;
+        }
+      }
     }
   }
 
diff --git a/app/helpers/merge_requests_helper.rb b/app/helpers/merge_requests_helper.rb
index 8c2c4e8833b..83ff898e68a 100644
--- a/app/helpers/merge_requests_helper.rb
+++ b/app/helpers/merge_requests_helper.rb
@@ -143,4 +143,16 @@ module MergeRequestsHelper
   def different_base?(version1, version2)
     version1 && version2 && version1.base_commit_sha != version2.base_commit_sha
   end
+
+  def merge_params(merge_request)
+    {
+      merge_when_build_succeeds: true,
+      should_remove_source_branch: true,
+      sha: merge_request.diff_head_sha
+    }.merge(merge_params_ee(merge_request))
+  end
+
+  def merge_params_ee(merge_request)
+    {}
+  end
 end
diff --git a/app/models/repository.rb b/app/models/repository.rb
index d77b7692d75..bd8f34e4cad 100644
--- a/app/models/repository.rb
+++ b/app/models/repository.rb
@@ -932,9 +932,9 @@ class Repository
     end
   end
 
-  def merge(user, merge_request, options = {})
+  def merge(user, source, merge_request, options = {})
     our_commit = rugged.branches[merge_request.target_branch].target
-    their_commit = rugged.lookup(merge_request.diff_head_sha)
+    their_commit = rugged.lookup(source)
 
     raise "Invalid merge target" if our_commit.nil?
     raise "Invalid merge source" if their_commit.nil?
diff --git a/app/services/merge_requests/merge_service.rb b/app/services/merge_requests/merge_service.rb
index ab9056a3250..5ca6fec962d 100644
--- a/app/services/merge_requests/merge_service.rb
+++ b/app/services/merge_requests/merge_service.rb
@@ -6,13 +6,17 @@ module MergeRequests
   # Executed when you do merge via GitLab UI
   #
   class MergeService < MergeRequests::BaseService
-    attr_reader :merge_request
+    attr_reader :merge_request, :source
 
     def execute(merge_request)
       @merge_request = merge_request
 
       return log_merge_error('Merge request is not mergeable', true) unless @merge_request.mergeable?
 
+      @source = find_merge_source
+
+      return log_merge_error('No source for merge', true) unless @source
+
       merge_request.in_locked_state do
         if commit
           after_merge
@@ -34,7 +38,7 @@ module MergeRequests
         committer: committer
       }
 
-      commit_id = repository.merge(current_user, merge_request, options)
+      commit_id = repository.merge(current_user, source, merge_request, options)
 
       if commit_id
         merge_request.update(merge_commit_sha: commit_id)
@@ -73,9 +77,11 @@ module MergeRequests
     end
 
     def merge_request_info
-      project = merge_request.project
+      merge_request.to_reference(full: true)
+    end
 
-      "#{project.to_reference}#{merge_request.to_reference}"
+    def find_merge_source
+      merge_request.diff_head_sha
     end
   end
 end
diff --git a/app/views/projects/merge_requests/widget/open/_accept.html.haml b/app/views/projects/merge_requests/widget/open/_accept.html.haml
index 7809e9c8c72..39cb0ca9cdc 100644
--- a/app/views/projects/merge_requests/widget/open/_accept.html.haml
+++ b/app/views/projects/merge_requests/widget/open/_accept.html.haml
@@ -35,10 +35,10 @@
           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.right
+      .accept-control
         = link_to "#", class: "modify-merge-commit-link js-toggle-button" do
           = icon('edit')
           Modify commit message
diff --git a/app/views/projects/merge_requests/widget/open/_merge_when_build_succeeds.html.haml b/app/views/projects/merge_requests/widget/open/_merge_when_build_succeeds.html.haml
index f70cd09c5f4..304b0afcf93 100644
--- a/app/views/projects/merge_requests/widget/open/_merge_when_build_succeeds.html.haml
+++ b/app/views/projects/merge_requests/widget/open/_merge_when_build_succeeds.html.haml
@@ -19,7 +19,7 @@
   - if remove_source_branch_button || user_can_cancel_automatic_merge
     .clearfix.prepend-top-10
       - if remove_source_branch_button
-        = link_to merge_namespace_project_merge_request_path(@merge_request.target_project.namespace, @merge_request.target_project, @merge_request, merge_when_build_succeeds: true, should_remove_source_branch: true, sha: @merge_request.diff_head_sha), remote: true, method: :post, class: "btn btn-grouped btn-primary btn-sm remove_source_branch" do
+        = link_to merge_namespace_project_merge_request_path(@merge_request.target_project.namespace, @merge_request.target_project, @merge_request, merge_params(@merge_request)), remote: true, method: :post, class: "btn btn-grouped btn-primary btn-sm remove_source_branch" do
           = icon('times')
           Remove Source Branch When Merged
 
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index 0a4de709fcd..cb92b2e97a7 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -43,6 +43,8 @@
 
 = render 'shared/issuable/form/branch_chooser', issuable: issuable, form: form
 
+= render 'shared/issuable/form/merge_params', issuable: issuable
+
 - if @merge_request_for_resolving_discussions
   .form-group
     .col-sm-10.col-sm-offset-2
diff --git a/app/views/shared/issuable/form/_branch_chooser.html.haml b/app/views/shared/issuable/form/_branch_chooser.html.haml
index b757893ea04..2793e7bcff4 100644
--- a/app/views/shared/issuable/form/_branch_chooser.html.haml
+++ b/app/views/shared/issuable/form/_branch_chooser.html.haml
@@ -19,12 +19,3 @@
     - if issuable.new_record?
       &nbsp;
       = link_to 'Change branches', mr_change_branches_path(issuable)
-
-- if issuable.can_remove_source_branch?(current_user)
-  .form-group
-    .col-sm-10.col-sm-offset-2
-      .checkbox
-        = label_tag 'merge_request[force_remove_source_branch]' do
-          = 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.
diff --git a/app/views/shared/issuable/form/_merge_params.html.haml b/app/views/shared/issuable/form/_merge_params.html.haml
new file mode 100644
index 00000000000..03309722326
--- /dev/null
+++ b/app/views/shared/issuable/form/_merge_params.html.haml
@@ -0,0 +1,16 @@
+- issuable = local_assigns.fetch(:issuable)
+
+- return unless issuable.is_a?(MergeRequest)
+- return if issuable.closed_without_fork?
+
+-# This check is duplicated below, to avoid conflicts with EE.
+- return unless issuable.can_remove_source_branch?(current_user)
+
+.form-group
+  .col-sm-10.col-sm-offset-2
+    - if issuable.can_remove_source_branch?(current_user)
+      .checkbox
+        = label_tag 'merge_request[force_remove_source_branch]' do
+          = 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.
diff --git a/spec/lib/gitlab/diff/position_tracer_spec.rb b/spec/lib/gitlab/diff/position_tracer_spec.rb
index f5822fed37c..21781535793 100644
--- a/spec/lib/gitlab/diff/position_tracer_spec.rb
+++ b/spec/lib/gitlab/diff/position_tracer_spec.rb
@@ -1640,7 +1640,9 @@ describe Gitlab::Diff::PositionTracer, lib: true do
         }
 
         merge_request = create(:merge_request, source_branch: second_create_file_commit.sha, target_branch: branch_name, source_project: project)
-        repository.merge(current_user, merge_request, options)
+
+        repository.merge(current_user, merge_request.diff_head_sha, merge_request, options)
+
         project.commit(branch_name)
       end
 
diff --git a/spec/models/repository_spec.rb b/spec/models/repository_spec.rb
index 829b69093c9..775bdc91d70 100644
--- a/spec/models/repository_spec.rb
+++ b/spec/models/repository_spec.rb
@@ -15,7 +15,12 @@ describe Repository, models: true do
 
   let(:merge_commit) do
     merge_request = create(:merge_request, source_branch: 'feature', target_branch: 'master', source_project: project)
-    merge_commit_id = repository.merge(user, merge_request, commit_options)
+
+    merge_commit_id = repository.merge(user,
+                                       merge_request.diff_head_sha,
+                                       merge_request,
+                                       commit_options)
+
     repository.commit(merge_commit_id)
   end
 
@@ -1009,8 +1014,11 @@ describe Repository, models: true do
 
     it 'sets the `in_progress_merge_commit_sha` flag for the given merge request' do
       merge_request = create(:merge_request, source_branch: 'feature', target_branch: 'master', source_project: project)
-      merge_commit_id = repository.merge(user, merge_request, commit_options)
-      repository.commit(merge_commit_id)
+
+      merge_commit_id = repository.merge(user,
+                                         merge_request.diff_head_sha,
+                                         merge_request,
+                                         commit_options)
 
       expect(merge_request.in_progress_merge_commit_sha).to eq(merge_commit_id)
     end
diff --git a/spec/services/merge_requests/refresh_service_spec.rb b/spec/services/merge_requests/refresh_service_spec.rb
index 314ea670a71..2cc21acab7b 100644
--- a/spec/services/merge_requests/refresh_service_spec.rb
+++ b/spec/services/merge_requests/refresh_service_spec.rb
@@ -89,7 +89,7 @@ describe MergeRequests::RefreshService, services: true do
         # Merge master -> feature branch
         author = { email: 'test@gitlab.com', time: Time.now, name: "Me" }
         commit_options = { message: 'Test message', committer: author, author: author }
-        @project.repository.merge(@user, @merge_request, commit_options)
+        @project.repository.merge(@user, @merge_request.diff_head_sha, @merge_request, commit_options)
         commit = @project.repository.commit('feature')
         service.new(@project, @user).execute(@oldrev, commit.id, 'refs/heads/feature')
         reload_mrs
diff --git a/spec/support/test_env.rb b/spec/support/test_env.rb
index 90f1a9c8798..b87232a350b 100644
--- a/spec/support/test_env.rb
+++ b/spec/support/test_env.rb
@@ -36,7 +36,8 @@ module TestEnv
     'conflict-non-utf8'                  => 'd0a293c',
     'conflict-too-large'                 => '39fa04f',
     'deleted-image-test'                 => '6c17798',
-    'wip'                                => 'b9238ee'
+    'wip'                                => 'b9238ee',
+    'csv'                                => '3dd0896'
   }
 
   # gitlab-test-fork is a fork of gitlab-fork, but we don't necessarily