Merge branch '29541-fix-github-importer-deleted-fork' into 'master'

Fix GitHub importer for PRs of deleted forked repositories

Closes #29541

See merge request !9992

2 files changed, 30 insertions, 11 deletions

diff --git a/lib/gitlab/github_import/branch_formatter.rb b/lib/gitlab/github_import/branch_formatter.rb
index 0a8d05b5fe1..e7c6d2d5346 100644
--- a/lib/gitlab/github_import/branch_formatter.rb
+++ b/lib/gitlab/github_import/branch_formatter.rb
@@ -11,6 +11,14 @@ module Gitlab
         sha.present? && ref.present?
       end
 
+      def user
+        raw_data.user&.login || 'unknown'
+      end
+
+      def short_sha
+        Commit.truncate_sha(sha)
+      end
+
       private
 
       def branch_exists?
diff --git a/lib/gitlab/github_import/pull_request_formatter.rb b/lib/gitlab/github_import/pull_request_formatter.rb
index 28812fd0cb9..6d57ac335eb 100644
--- a/lib/gitlab/github_import/pull_request_formatter.rb
+++ b/lib/gitlab/github_import/pull_request_formatter.rb
@@ -1,8 +1,8 @@
 module Gitlab
   module GithubImport
     class PullRequestFormatter < IssuableFormatter
-      delegate :exists?, :project, :ref, :repo, :sha, to: :source_branch, prefix: true
-      delegate :exists?, :project, :ref, :repo, :sha, to: :target_branch, prefix: true
+      delegate :user, :project, :ref, :repo, :sha, to: :source_branch, prefix: true
+      delegate :user, :exists?, :project, :ref, :repo, :sha, :short_sha, to: :target_branch, prefix: true
 
       def attributes
         {
@@ -37,13 +37,20 @@ module Gitlab
       end
 
       def source_branch_name
-        @source_branch_name ||= begin
-          if cross_project?
-            "pull/#{number}/#{source_branch_repo.full_name}/#{source_branch_ref}"
+        @source_branch_name ||=
+          if cross_project? || !source_branch_exists?
+            source_branch_name_prefixed
           else
-            source_branch_exists? ? source_branch_ref : "pull/#{number}/#{source_branch_ref}"
+            source_branch_ref
           end
-        end
+      end
+
+      def source_branch_name_prefixed
+        "gh-#{target_branch_short_sha}/#{number}/#{source_branch_user}/#{source_branch_ref}"
+      end
+
+      def source_branch_exists?
+        !cross_project? && source_branch.exists?
       end
 
       def target_branch
@@ -51,13 +58,17 @@ module Gitlab
       end
 
       def target_branch_name
-        @target_branch_name ||= begin
-          target_branch_exists? ? target_branch_ref : "pull/#{number}/#{target_branch_ref}"
-        end
+        @target_branch_name ||= target_branch_exists? ? target_branch_ref : target_branch_name_prefixed
+      end
+
+      def target_branch_name_prefixed
+        "gl-#{target_branch_short_sha}/#{number}/#{target_branch_user}/#{target_branch_ref}"
       end
 
       def cross_project?
-        source_branch.repo.id != target_branch.repo.id
+        return true if source_branch_repo.nil?
+
+        source_branch_repo.id != target_branch_repo.id
       end
 
       private