1 files changed, 70 insertions, 0 deletions
diff --git a/app/graphql/mutations/projects/sync_fork.rb b/app/graphql/mutations/projects/sync_fork.rb
new file mode 100644
index 00000000000..4520f6388c5
--- /dev/null
+++ b/app/graphql/mutations/projects/sync_fork.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Projects
+    class SyncFork < BaseMutation
+      graphql_name 'ProjectSyncFork'
+
+      include FindsProject
+
+      argument :project_path, GraphQL::Types::ID,
+        required: true,
+        description: 'Full path of the project to initialize.'
+
+      argument :target_branch, GraphQL::Types::String,
+        required: true,
+        description: 'Ref of the fork to fetch into.'
+
+      field :details, Types::Projects::ForkDetailsType,
+        null: true,
+        description: 'Updated fork details.'
+
+      def resolve(project_path:, target_branch:)
+        project = authorized_find!(project_path, target_branch)
+
+        return respond(nil, ['Feature flag is disabled']) unless Feature.enabled?(:synchronize_fork,
+          project.fork_source)
+
+        return respond(nil, ['Target branch does not exist']) unless project.repository.branch_exists?(target_branch)
+
+        details_resolver = Resolvers::Projects::ForkDetailsResolver.new(object: project, context: context, field: nil)
+        details = details_resolver.resolve(ref: target_branch)
+
+        return respond(nil, ['This branch of this project cannot be updated from the upstream']) unless details
+
+        enqueue_sync_fork(project, target_branch, details)
+      end
+
+      def enqueue_sync_fork(project, target_branch, details)
+        return respond(details, []) if details.counts[:behind] == 0
+
+        if details.has_conflicts?
+          return respond(details, ['The synchronization cannot happen due to the merge conflict'])
+        end
+
+        return respond(details, ['This service has been called too many times.']) if rate_limit_throttled?(project)
+        return respond(details, ['Another fork sync is already in progress']) unless details.exclusive_lease.try_obtain
+
+        ::Projects::Forks::SyncWorker.perform_async(project.id, current_user.id, target_branch) # rubocop:disable CodeReuse/Worker
+
+        respond(details, [])
+      end
+
+      def rate_limit_throttled?(project)
+        Gitlab::ApplicationRateLimiter.throttled?(:project_fork_sync, scope: [project, current_user])
+      end
+
+      def respond(details, errors)
+        { details: details, errors: errors }
+      end
+
+      def authorized_find!(project_path, target_branch)
+        project = find_object(project_path)
+
+        return project if ::Gitlab::UserAccess.new(current_user, container: project).can_push_to_branch?(target_branch)
+
+        raise_resource_not_available_error!
+      end
+    end
+  end
+end