Prefixes removed branches name with PR number when importing PR from GH

lib/gitlab/github_import/branch_formatter.rb

@@ -7,10 +7,6 @@ module Gitlab
         branch_exists? && commit_exists?
       end
 
-      def name
-        ref
-      end
-
       def valid?
         repo.present?
       end

lib/gitlab/github_import/pull_request_formatter.rb

 module Gitlab
   module GithubImport
     class PullRequestFormatter < BaseFormatter
-      delegate :exists?, :name, :project, :repo, :sha, to: :source_branch, prefix: true
-      delegate :exists?, :name, :project, :repo, :sha, to: :target_branch, prefix: true
+      delegate :exists?, :project, :ref, :repo, :sha, to: :source_branch, prefix: true
+      delegate :exists?, :project, :ref, :repo, :sha, to: :target_branch, prefix: true
 
       def attributes
         {
@@ -40,10 +40,22 @@ module Gitlab
         @source_branch ||= BranchFormatter.new(project, raw_data.head)
       end
 
+      def source_branch_name
+        @source_branch_name ||= begin
+          source_branch_exists? ? source_branch_ref : "pull/#{number}/#{source_branch_ref}"
+        end
+      end
+
       def target_branch
         @target_branch ||= BranchFormatter.new(project, raw_data.base)
       end
 
+      def target_branch_name
+        @target_branch_name ||= begin
+          target_branch_exists? ? target_branch_ref : "pull/#{number}/#{target_branch_ref}"
+        end
+      end
+
       private
 
       def assigned?

spec/lib/gitlab/github_import/branch_formatter_spec.rb

@@ -32,14 +32,6 @@ describe Gitlab::GithubImport::BranchFormatter, lib: true do
     end
   end
 
-  describe '#name' do
-    it 'returns raw ref' do
-      branch = described_class.new(project, double(raw))
-
-      expect(branch.name).to eq 'feature'
-    end
-  end
-
   describe '#repo' do
     it 'returns raw repo' do
       branch = described_class.new(project, double(raw))

spec/lib/gitlab/github_import/pull_request_formatter_spec.rb

@@ -9,6 +9,7 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
   let(:source_branch) { double(ref: 'feature', repo: source_repo, sha: source_sha) }
   let(:target_repo) { repository }
   let(:target_branch) { double(ref: 'master', repo: target_repo, sha: target_sha) }
+  let(:removed_branch) { double(ref: 'removed-branch', repo: source_repo, sha: '2e5d3239642f9161dcbbc4b70a211a68e5e45e2b') }
   let(:octocat) { double(id: 123456, login: 'octocat') }
   let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
   let(:updated_at) { DateTime.strptime('2011-01-27T19:01:12Z') }
@@ -165,6 +166,42 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
     end
   end
 
+  describe '#source_branch_name' do
+    context 'when source branch exists' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns branch ref' do
+        expect(pull_request.source_branch_name).to eq 'feature'
+      end
+    end
+
+    context 'when source branch does not exist' do
+      let(:raw_data) { double(base_data.merge(head: removed_branch)) }
+
+      it 'prefixes branch name with pull request number' do
+        expect(pull_request.source_branch_name).to eq 'pull/1347/removed-branch'
+      end
+    end
+  end
+
+  describe '#target_branch_name' do
+    context 'when source branch exists' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns branch ref' do
+        expect(pull_request.target_branch_name).to eq 'master'
+      end
+    end
+
+    context 'when target branch does not exist' do
+      let(:raw_data) { double(base_data.merge(base: removed_branch)) }
+
+      it 'prefixes branch name with pull request number' do
+        expect(pull_request.target_branch_name).to eq 'pull/1347/removed-branch'
+      end
+    end
+  end
+
   describe '#valid?' do
     context 'when source, and target repos are not a fork' do
       let(:raw_data) { double(base_data) }