Fix importing projects from GitHub Enterprise Edition

CHANGELOG-EE

 Please view this file on the master branch, on stable branches it's out of date.
 
+v 8.5.2
+  - Fix importing projects from GitHub Enterprise Edition.
+
 v 8.5.1
   - Fix adding pages domain to projects in groups
 

lib/gitlab/github_import/client.rb

@@ -42,11 +42,11 @@ module Gitlab
       private
 
       def config
-        Gitlab.config.omniauth.providers.find { |provider| provider.name == "github"}
+        Gitlab.config.omniauth.providers.find { |provider| provider.name == "github" }
       end
 
       def github_options
-        OmniAuth::Strategies::GitHub.default_options[:client_options].to_h.symbolize_keys
+        config["args"]["client_options"].deep_symbolize_keys
       end
     end
   end

spec/lib/gitlab/github_import/client_spec.rb

@@ -2,16 +2,34 @@ require 'spec_helper'
 
 describe Gitlab::GithubImport::Client, lib: true do
   let(:token) { '123456' }
-  let(:client) { Gitlab::GithubImport::Client.new(token) }
+  let(:github_provider) { OpenStruct.new(app_id: 'asd123', app_secret: 'asd123', name: 'github', args: { 'client_options' => {} }) }
+
+  subject(:client) { described_class.new(token) }
 
   before do
-    github_provider = OpenStruct.new(app_id: "asd123", app_secret: "asd123", name: "github", args: { "client_options" => {} })
     allow(Gitlab.config.omniauth).to receive(:providers).and_return([github_provider])
   end
 
-  it 'all OAuth2 client options are symbols' do
+  it 'convert OAuth2 client options to symbols' do
     client.client.options.keys.each do |key|
       expect(key).to be_kind_of(Symbol)
     end
   end
+
+  context 'when provider does not specity an API endpoint' do
+    it 'uses GitHub root API endpoint' do
+      expect(client.api.api_endpoint).to eq 'https://api.github.com/'
+    end
+  end
+
+  context 'when provider specify a custom API endpoint' do
+    before do
+      github_provider['args']['client_options']['site'] = 'https://github.company.com/'
+    end
+
+    it 'uses the custom API endpoint' do
+      expect(OmniAuth::Strategies::GitHub).not_to receive(:default_options)
+      expect(client.api.api_endpoint).to eq 'https://github.company.com/'
+    end
+  end
 end