Prefixes source branch name with short SHA to avoid collision

lib/gitlab/github_import/branch_formatter.rb

@@ -15,6 +15,10 @@ module Gitlab
         raw_data.user.login
       end
 
+      def short_sha(length = 7)
+        sha.to_s[0..length]
+      end
+
       private
 
       def branch_exists?

lib/gitlab/github_import/pull_request_formatter.rb

 module Gitlab
   module GithubImport
     class PullRequestFormatter < IssuableFormatter
-      delegate :user, :exists?, :project, :ref, :repo, :sha, to: :source_branch, prefix: true
-      delegate :user, :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
         {
@@ -39,17 +39,17 @@ module Gitlab
       def source_branch_name
         @source_branch_name ||= begin
           if cross_project?
-            if source_branch_repo
-              "pull/#{number}/#{source_branch_repo.full_name}/#{source_branch_ref}"
-            else
-              "pull/#{number}/#{source_branch_user}/#{source_branch_ref}"
-            end
+            source_branch_name_prefixed
           else
-            source_branch_exists? ? source_branch_ref : "pull/#{number}/#{source_branch_ref}"
+            source_branch_exists? ? source_branch_ref : source_branch_name_prefixed
           end
         end
       end
 
+      def source_branch_name_prefixed
+        "gh-#{target_branch_short_sha}/#{number}"
+      end
+
       def source_branch_exists?
         return false if cross_project?
 
@@ -62,10 +62,14 @@ module Gitlab
 
       def target_branch_name
         @target_branch_name ||= begin
-          target_branch_exists? ? target_branch_ref : "pull/#{number}/#{target_branch_ref}"
+          target_branch_exists? ? target_branch_ref : target_branch_name_prefixed
         end
       end
 
+      def target_branch_name_prefixed
+        "gl-#{target_branch_short_sha}/#{number}"
+      end
+
       def cross_project?
         return true if source_branch_repo.nil?
 

spec/lib/gitlab/github_import/pull_request_formatter_spec.rb

@@ -4,7 +4,9 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
   let(:client) { double }
   let(:project) { create(:project, :repository) }
   let(:source_sha) { create(:commit, project: project).id }
-  let(:target_sha) { create(:commit, project: project, git_commit: RepoHelpers.another_sample_commit).id }
+  let(:target_commit) { create(:commit, project: project, git_commit: RepoHelpers.another_sample_commit) }
+  let(:target_sha) { target_commit.id }
+  let(:target_short_sha) { target_commit.id.to_s[0..7] }
   let(:repository) { double(id: 1, fork: false) }
   let(:source_repo) { repository }
   let(:source_branch) { double(ref: 'branch-merged', repo: source_repo, sha: source_sha) }
@@ -204,24 +206,24 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
     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'
+      it 'prefixes branch name with to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347"
       end
     end
 
     context 'when source branch is from a fork' do
       let(:raw_data) { double(base_data.merge(head: forked_branch)) }
 
-      it 'prefixes branch name with pull request number and project with namespace to avoid collision' do
-        expect(pull_request.source_branch_name).to eq 'pull/1347/company/otherproject/master'
+      it 'prefixes branch name with to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347"
       end
     end
 
     context 'when source branch is from a deleted fork' do
       let(:raw_data) { double(base_data.merge(head: branch_deleted_repo)) }
 
-      it 'prefixes branch name with pull request number and user login to avoid collision' do
-        expect(pull_request.source_branch_name).to eq 'pull/1347/octocat/master'
+      it 'prefixes branch name with to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347"
       end
     end
   end
@@ -238,8 +240,8 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
     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'
+      it 'prefixes branch name with to avoid collision' do
+        expect(pull_request.target_branch_name).to eq 'gl-2e5d3239/1347'
       end
     end
   end