Adds option to overwrite a diverged branch when mirroring

changelogs/unreleased-ee/4723-add-option-to-overwrite-diverged-branches-when-pull-mirroring.yml

+---
+title: Add option to overwrite diverged branches for pull mirrors
+merge_request: 4559
+author:
+type: added

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180213131630) do
+ActiveRecord::Schema.define(version: 20180215143644) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1913,6 +1913,7 @@ ActiveRecord::Schema.define(version: 20180213131630) do
     t.boolean "only_mirror_protected_branches"
     t.boolean "pull_mirror_available_overridden"
     t.integer "jobs_cache_index"
+    t.boolean "mirror_overwrites_diverged_branches"
   end
 
   add_index "projects", ["ci_id"], name: "index_projects_on_ci_id", using: :btree

doc/workflow/repository_mirroring.md

@@ -102,6 +102,15 @@ You can choose to only pull the protected branches from your remote repository t
 
 To use this option go to your project's repository settings page under pull mirror.
 
+### Overwrite diverged branches
+
+>[Introduced][ee-4559] in GitLab Enterprise Edition 10.6.
+
+You can choose to always update your local branch with the remote version even 
+if your local version has diverged from the remote.
+
+To use this option go to your project's repository settings page under pull mirror.
+
 ### Hard failure
 
 >[Introduced][ee-3117] in GitLab Enterprise Edition 10.2.

ee/app/controllers/projects/mirrors_controller.rb

@@ -81,6 +81,7 @@ class Projects::MirrorsController < Projects::ApplicationController
       :mirror_user_id,
       :mirror_trigger_builds,
       :only_mirror_protected_branches,
+      :mirror_overwrites_diverged_branches,
 
       import_data_attributes: %i[
         id

ee/app/serializers/project_mirror_entity.rb

@@ -5,6 +5,8 @@ class ProjectMirrorEntity < Grape::Entity
   expose :username_only_import_url
   expose :mirror_user_id
   expose :mirror_trigger_builds
+  expose :only_mirror_protected_branches
+  expose :mirror_overwrites_diverged_branches
 
   expose :import_data_attributes do |project|
     import_data = project.import_data

ee/app/services/projects/update_mirror_service.rb

@@ -45,10 +45,7 @@ module Projects
         elsif local_branch.dereferenced_target == upstream_branch.dereferenced_target
           # Already up to date
         elsif repository.diverged_from_upstream?(name)
-          # Cannot be updated
-          if name == project.default_branch
-            errors << "The default branch (#{project.default_branch}) has diverged from its upstream counterpart and could not be updated automatically."
-          end
+          handle_diverged_branch(upstream_branch, local_branch, name, errors)
         else
           begin
             repository.ff_merge(current_user, upstream_branch.dereferenced_target, name)
@@ -95,6 +92,20 @@ module Projects
       fetch_result
     end
 
+    def handle_diverged_branch(upstream, local, branch_name, errors)
+      if project.mirror_overwrites_diverged_branches?
+        newrev = upstream.dereferenced_target.sha
+        oldrev = local.dereferenced_target.sha
+
+        repository.update_branch(current_user, branch_name, newrev, oldrev)
+      elsif branch_name == project.default_branch
+        # Cannot be updated
+        errors << "The default branch (#{project.default_branch}) has diverged from its upstream counterpart and could not be updated automatically."
+      else
+        # We ignore diverged branches other than the default branch
+      end
+    end
+
     # In Git is possible to tag blob objects, and those blob objects don't point to a Git commit so those tags
     # have no target.
     def repository_tags_with_target

ee/app/views/projects/mirrors/_pull.html.haml

@@ -47,6 +47,15 @@
           = f.label :only_mirror_protected_branches, class: 'label-light'
           = link_to icon('question-circle'), help_page_path('user/project/protected_branches')
 
+      .form-group
+        = f.check_box :mirror_overwrites_diverged_branches, class: 'pull-left'
+        .prepend-left-20
+          = f.label :mirror_overwrites_diverged_branches, "Overwrite diverged branches", class: 'label-light'
+          .help-block
+            If disabled, a diverged local branch will not be automatically updated with commits from its remote counterpart,
+            to prevent local data loss. If the default branch (#{@project.default_branch}) has diverged and cannot be updated,
+            mirroring will fail. Other diverged branches are silently ignored.
+
       - if @project.builds_enabled?
         = render "shared/mirror_trigger_builds_setting", f: f
 

ee/db/migrate/20180215143644_add_mirror_overwrites_diverged_branches_to_project.rb

+class AddMirrorOverwritesDivergedBranchesToProject < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def change
+    add_column :projects, :mirror_overwrites_diverged_branches, :boolean
+  end
+end

ee/spec/serializers/project_mirror_entity_spec.rb

@@ -20,6 +20,8 @@ describe ProjectMirrorEntity do
           username_only_import_url: project.username_only_import_url,
           mirror_user_id: project.mirror_user_id,
           mirror_trigger_builds: project.mirror_trigger_builds,
+          only_mirror_protected_branches: project.only_mirror_protected_branches,
+          mirror_overwrites_diverged_branches: project.mirror_overwrites_diverged_branches,
           import_data_attributes: {
             id: import_data.id,
             auth_method: 'password',
@@ -48,6 +50,8 @@ describe ProjectMirrorEntity do
           username_only_import_url: project.username_only_import_url,
           mirror_user_id: project.mirror_user_id,
           mirror_trigger_builds: project.mirror_trigger_builds,
+          only_mirror_protected_branches: project.only_mirror_protected_branches,
+          mirror_overwrites_diverged_branches: project.mirror_overwrites_diverged_branches,
           import_data_attributes: {
             id: import_data.id,
             auth_method: 'ssh_public_key',
@@ -75,6 +79,8 @@ describe ProjectMirrorEntity do
         username_only_import_url: nil,
         mirror_user_id: nil,
         mirror_trigger_builds: false,
+        only_mirror_protected_branches: true,
+        mirror_overwrites_diverged_branches: nil,
         import_data_attributes: nil,
         remote_mirrors_attributes: [
           {

ee/spec/services/projects/update_mirror_service_spec.rb

@@ -55,6 +55,8 @@ describe Projects::UpdateMirrorService do
     end
 
     describe "updating branches" do
+      subject { described_class.new(project, project.owner) }
+
       context 'when mirror only protected branches option is set' do
         let(:new_protected_branch_name) { 'new-branch' }
         let(:protected_branch_name) { 'existing-branch' }
@@ -69,7 +71,7 @@ describe Projects::UpdateMirrorService do
 
           stub_fetch_mirror(project)
 
-          described_class.new(project, project.owner).execute
+          subject.execute
 
           expect(project.repository.branch_names).to include(new_protected_branch_name)
         end
@@ -88,7 +90,7 @@ describe Projects::UpdateMirrorService do
 
           stub_fetch_mirror(project)
 
-          described_class.new(project, project.owner).execute
+          subject.execute
 
           expect(project.repository.find_branch(protected_branch_name).dereferenced_target)
             .to eq(project.repository.find_branch('master').dereferenced_target)
@@ -97,7 +99,7 @@ describe Projects::UpdateMirrorService do
         it "does not update unprotected branches" do
           stub_fetch_mirror(project)
 
-          described_class.new(project, project.owner).execute
+          subject.execute
 
           expect(project.repository.find_branch(protected_branch_name).dereferenced_target)
             .not_to eq(project.repository.find_branch('master').dereferenced_target)
@@ -107,7 +109,7 @@ describe Projects::UpdateMirrorService do
       it "creates new branches" do
         stub_fetch_mirror(project)
 
-        described_class.new(project, project.owner).execute
+        subject.execute
 
         expect(project.repository.branch_names).to include('new-branch')
       end
@@ -115,19 +117,49 @@ describe Projects::UpdateMirrorService do
       it "updates existing branches" do
         stub_fetch_mirror(project)
 
-        described_class.new(project, project.owner).execute
+        subject.execute
 
         expect(project.repository.find_branch('existing-branch').dereferenced_target)
           .to eq(project.repository.find_branch('master').dereferenced_target)
       end
 
-      it "doesn't update diverged branches" do
-        stub_fetch_mirror(project)
+      context 'with diverged branches' do
+        before do
+          stub_fetch_mirror(project)
+        end
 
-        described_class.new(project, project.owner).execute
+        context 'when mirror_overwrites_diverged_branches is true' do
+          it 'update diverged branches' do
+            project.mirror_overwrites_diverged_branches = true
 
-        expect(project.repository.find_branch('markdown').dereferenced_target)
-          .not_to eq(project.repository.find_branch('master').dereferenced_target)
+            subject.execute
+
+            expect(project.repository.find_branch('markdown').dereferenced_target)
+                .to eq(project.repository.find_branch('master').dereferenced_target)
+          end
+        end
+
+        context 'when mirror_overwrites_diverged_branches is false' do
+          it "doesn't update diverged branches" do
+            project.mirror_overwrites_diverged_branches = false
+
+            subject.execute
+
+            expect(project.repository.find_branch('markdown').dereferenced_target)
+                .not_to eq(project.repository.find_branch('master').dereferenced_target)
+          end
+        end
+
+        context 'when mirror_overwrites_diverged_branches is nil' do
+          it "doesn't update diverged branches" do
+            project.mirror_overwrites_diverged_branches = nil
+
+            subject.execute
+
+            expect(project.repository.find_branch('markdown').dereferenced_target)
+                .not_to eq(project.repository.find_branch('master').dereferenced_target)
+          end
+        end
       end
 
       describe 'when project is empty' do
@@ -139,7 +171,7 @@ describe Projects::UpdateMirrorService do
           allow(project).to receive(:fetch_mirror) { create_file(repository) }
           expect(CreateBranchService).not_to receive(:create_master_branch)
 
-          described_class.new(project, project.owner).execute
+          subject.execute
 
           expect(repository.branch_names).not_to include('master')
         end

lib/gitlab/git/repository.rb

@@ -939,6 +939,10 @@ module Gitlab
         nil
       end
 
+      def update_branch(user, branch_name, newrev, oldrev)
+        Gitlab::Git::OperationService.new(user, self).update_branch(branch_name, newrev, oldrev)
+      end
+
       AUTOCRLF_VALUES = {
         "true" => true,
         "false" => false,

lib/gitlab/import_export/import_export.yml

@@ -111,6 +111,7 @@ excluded_attributes:
     - :remote_mirror_available_overridden
     - :only_mirror_protected_branches
     - :pull_mirror_available_overridden
+    - :mirror_overwrites_diverged_branches
   snippets:
     - :expired_at
   merge_request_diff: