2 files changed, 50 insertions, 10 deletions

diff --git a/lib/gitlab/github_import/pull_request_formatter.rb b/lib/gitlab/github_import/pull_request_formatter.rb
index 3b541a04d5c..9f8182f643e 100644
--- a/lib/gitlab/github_import/pull_request_formatter.rb
+++ b/lib/gitlab/github_import/pull_request_formatter.rb
@@ -30,11 +30,19 @@ module Gitlab
       end
 
       def source_branch_exists?
-        source_project.repository.branch_names.include?(source_branch)
+        source_project.repository.branch_exists?(source_ref)
       end
 
       def source_branch
-        raw_data.head.ref
+        @source_branch ||= if source_branch_exists?
+                             source_ref
+                           else
+                             "#{source_ref}-#{short_id(source_sha)}"
+                           end
+      end
+
+      def short_id(sha, length = 7)
+        sha.to_s[0..length]
       end
 
       def source_sha
@@ -42,11 +50,15 @@ module Gitlab
       end
 
       def target_branch_exists?
-        target_project.repository.branch_names.include?(target_branch)
+        target_project.repository.branch_exists?(target_ref)
       end
 
       def target_branch
-        raw_data.base.ref
+        @target_branch ||= if target_branch_exists?
+                             target_ref
+                           else
+                             "#{target_ref}-#{short_id(target_sha)}"
+                           end
       end
 
       def target_sha
@@ -99,6 +111,10 @@ module Gitlab
         raw_data.head.repo
       end
 
+      def source_ref
+        raw_data.head.ref
+      end
+
       def target_project
         project
       end
@@ -107,6 +123,10 @@ module Gitlab
         raw_data.base.repo
       end
 
+      def target_ref
+        raw_data.base.ref
+      end
+
       def state
         @state ||= case true
                    when raw_data.state == 'closed' && raw_data.merged_at.present?
diff --git a/spec/lib/gitlab/github_import/pull_request_formatter_spec.rb b/spec/lib/gitlab/github_import/pull_request_formatter_spec.rb
index 1d15d3d937e..adedc57719e 100644
--- a/spec/lib/gitlab/github_import/pull_request_formatter_spec.rb
+++ b/spec/lib/gitlab/github_import/pull_request_formatter_spec.rb
@@ -164,10 +164,20 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
   end
 
   describe '#source_branch' do
-    let(:raw_data) { double(base_data) }
+    context 'when source branch exists' do
+      let(:raw_data) { double(base_data) }
 
-    it 'returns head ref' do
-      expect(pull_request.source_branch).to eq 'feature'
+      it 'returns head ref' do
+        expect(pull_request.source_branch).to eq 'feature'
+      end
+    end
+
+    context 'when source branch does not exist' do
+      let(:raw_data) { double(base_data.merge(head: double(ref: 'removed-branch', sha: '2e5d3239642f9161dcbbc4b70a211a68e5e45e2b'))) }
+
+      it 'returns head ref' do
+        expect(pull_request.source_branch).to eq 'removed-branch-2e5d3239'
+      end
     end
   end
 
@@ -198,10 +208,20 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
   end
 
   describe '#target_branch' do
-    let(:raw_data) { double(base_data) }
+    context 'when target branch exists' do
+      let(:raw_data) { double(base_data) }
 
-    it 'returns base ref' do
-      expect(pull_request.target_branch).to eq 'master'
+      it 'returns base ref' do
+        expect(pull_request.target_branch).to eq 'master'
+      end
+    end
+
+    context 'when target branch does not exist' do
+      let(:raw_data) { double(base_data.merge(base: double(ref: 'removed-branch', sha: '8ffb3c15a5475e59ae909384297fede4badcb4c7'))) }
+
+      it 'returns head ref' do
+        expect(pull_request.target_branch).to eq 'removed-branch-8ffb3c15'
+      end
     end
   end