Allow finding project by alias

This uses the ProjectAlias model. If an alias matches
the project_name specified, the associated project
will then be returned.

ee/app/models/project_alias.rb

+# frozen_string_literal: true
+
+class ProjectAlias < ApplicationRecord
+  belongs_to :project
+
+  validates :project, presence: true
+  validates :name, presence: true, uniqueness: true
+end

ee/lib/ee/gitlab/repo_path.rb

+# frozen_string_literal: true
+
+module EE
+  module Gitlab
+    module RepoPath
+      module ClassMethods
+        def find_project(project_path)
+          if project_alias = ProjectAlias.find_by_name(project_path)
+            [project_alias.project, false]
+          else
+            super(project_path)
+          end
+        end
+      end
+    end
+  end
+end

ee/spec/factories/project_aliases.rb

+FactoryBot.define do
+  factory :project_alias do
+    project
+    name { FFaker::Name.unique.name.parameterize }
+  end
+end

ee/spec/lib/ee/gitlab/repo_path_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::RepoPath do
+  describe '.find_project' do
+    let(:project) { create(:project) }
+
+    context 'project_path matches a project alias' do
+      let(:project_alias) { create(:project_alias, project: project) }
+
+      it 'returns the project' do
+        expect(described_class.find_project(project_alias.name)).to eq([project, false])
+      end
+    end
+
+    context 'project_path does not match a project alias' do
+      context 'project path matches project full path' do
+        it 'returns the project' do
+          expect(described_class.find_project(project.full_path)).to eq([project, false])
+        end
+      end
+
+      context 'project path does not match an existing project full path' do
+        it 'returns nil' do
+          expect(described_class.find_project('some-project')).to eq([nil, nil])
+        end
+      end
+    end
+  end
+end

ee/spec/models/project_alias_spec.rb

+require 'spec_helper'
+
+describe ProjectAlias do
+  subject { build(:project_alias) }
+
+  it { is_expected.to belong_to(:project) }
+
+  it { is_expected.to validate_presence_of(:project) }
+  it { is_expected.to validate_presence_of(:name) }
+  it { is_expected.to validate_uniqueness_of(:name) }
+end

lib/gitlab/repo_path.rb

@@ -38,3 +38,5 @@ module Gitlab
     end
   end
 end
+
+Gitlab::RepoPath.singleton_class.prepend(EE::Gitlab::RepoPath::ClassMethods)