Use owner for git actions during designs copy

When moving an issue we copy the design collection. Copying the design
collection involves adding commits to the design repository. Some users
have permission to move the issue (`:admin_issue` on the target
project), but not permission to push to the design repository of that
project and are being denied by
`GitAccessDesign#check_can_create_design!`.

Instead we now use the `Project#default_owner` to perform all of the git
actions instead of the `current_user`.

We still record the correct `Version#author` of the design in PostgreSQL
and still check the user can `:admin_issue` the target issue before
performing the copy.

https://gitlab.com/gitlab-org/gitlab/-/issues/263102

app/services/design_management/copy_design_collection/copy_service.rb

@@ -14,6 +14,9 @@ module DesignManagement
         @target_repository = @target_project.design_repository
         @target_design_collection = @target_issue.design_collection
         @temporary_branch = "CopyDesignCollectionService_#{SecureRandom.hex}"
+        # The user who triggered the copy may not have permissions to push
+        # to the design repository.
+        @git_user = @target_project.default_owner
 
         @designs = DesignManagement::Design.unscoped.where(issue: issue).order(:id).load
         @versions = DesignManagement::Version.unscoped.where(issue: issue).order(:id).includes(:designs).load
@@ -54,9 +57,9 @@ module DesignManagement
 
       private
 
-      attr_reader :designs, :event_enum_map, :sha_attribute, :shas, :temporary_branch,
-                  :target_design_collection, :target_issue, :target_repository,
-                  :target_project, :versions
+      attr_reader :designs, :event_enum_map, :git_user, :sha_attribute, :shas,
+                  :temporary_branch, :target_design_collection, :target_issue,
+                  :target_repository, :target_project, :versions
 
       alias_method :merge_branch, :target_branch
 
@@ -96,7 +99,7 @@ module DesignManagement
       # create `master` first by adding a file to it.
       def create_master_branch!
         target_repository.create_file(
-          current_user,
+          git_user,
           ".CopyDesignCollectionService_#{Time.now.to_i}",
           '.gitlab',
           message: "Commit to create #{merge_branch} branch in CopyDesignCollectionService",
@@ -106,7 +109,7 @@ module DesignManagement
 
       def create_temporary_branch!
         target_repository.add_branch(
-          current_user,
+          git_user,
           temporary_branch,
           target_repository.root_ref
         )
@@ -115,7 +118,7 @@ module DesignManagement
       def remove_temporary_branch!
         return unless target_repository.branch_exists?(temporary_branch)
 
-        target_repository.rm_branch(current_user, temporary_branch)
+        target_repository.rm_branch(git_user, temporary_branch)
       end
 
       # Merge the temporary branch containing the commits to `master`
@@ -124,7 +127,7 @@ module DesignManagement
         source_sha = shas.last
 
         target_repository.raw.merge(
-          current_user,
+          git_user,
           source_sha,
           merge_branch,
           'CopyDesignCollectionService finalize merge'
@@ -155,7 +158,7 @@ module DesignManagement
           end
 
           sha = target_repository.multi_action(
-            current_user,
+            git_user,
             branch_name: temporary_branch,
             message: commit_message(version),
             actions: gitaly_actions

changelogs/unreleased/263102-bugfix-use-project-owner-to-perform-git-actions-during-design-copy.yml

+---
+title: Perform git actions with a user with elevated git permissions during a design
+  copy
+merge_request: 44662
+author:
+type: fixed

spec/services/issues/move_service_spec.rb

@@ -205,6 +205,7 @@ RSpec.describe Issues::MoveService do
       end
 
       context 'issue with a design', :clean_gitlab_redis_shared_state do
+        let_it_be(:new_project) { create(:project) }
         let!(:design) { create(:design, :with_lfs_file, issue: old_issue) }
         let!(:note) { create(:diff_note_on_design, noteable: design, issue: old_issue, project: old_issue.project) }
         let(:subject) { move_service.execute(old_issue, new_project) }