Retrieve Git-specific env in Gitlab::Git::Repository#rugged

Signed-off-by: Rémy Coutable <remy@rymai.me>

lib/gitlab/git/repository.rb

@@ -8,6 +8,10 @@ module Gitlab
     class Repository
       include Gitlab::Git::Popen
+      ALLOWED_OBJECT_DIRECTORIES_VARIABLES = %w[
+        GIT_OBJECT_DIRECTORY
+        GIT_ALTERNATE_OBJECT_DIRECTORIES
+      ].freeze
       SEARCH_CONTEXT_LINES = 3
       NoRepository = Class.new(StandardError)
@@ -58,7 +62,7 @@ module Gitlab
       end
       def rugged
-        @rugged ||= Rugged::Repository.new(path)
+        @rugged ||= Rugged::Repository.new(path, alternates: alternate_object_directories)
       rescue Rugged::RepositoryError, Rugged::OSError
         raise NoRepository.new('no repository for such path')
       end
@@ -978,6 +982,10 @@ module Gitlab
       private
+      def alternate_object_directories
+        Gitlab::Git::Env.all.values_at(*ALLOWED_OBJECT_DIRECTORIES_VARIABLES).compact
+      end
+
       # Get the content of a blob for a given commit.  If the blob is a commit
       # (for submodules) then return the blob's OID.
       def blob_content(commit, blob_name)

spec/lib/gitlab/git/repository_spec.rb

@@ -40,6 +40,36 @@ describe Gitlab::Git::Repository, seed_helper: true do
     end
   end
+  describe "#rugged" do
+    context 'with no Git env stored' do
+      before do
+        expect(Gitlab::Git::Env).to receive(:all).and_return({})
+      end
+
+      it "whitelist some variables and pass them via the alternates keyword argument" do
+        expect(Rugged::Repository).to receive(:new).with(repository.path, alternates: [])
+
+        repository.rugged
+      end
+    end
+
+    context 'with some Git env stored' do
+      before do
+        expect(Gitlab::Git::Env).to receive(:all).and_return({
+          'GIT_OBJECT_DIRECTORY' => 'foo',
+          'GIT_ALTERNATE_OBJECT_DIRECTORIES' => 'bar',
+          'GIT_OTHER' => 'another_env'
+        })
+      end
+
+      it "whitelist some variables and pass them via the alternates keyword argument" do
+        expect(Rugged::Repository).to receive(:new).with(repository.path, alternates: %w[foo bar])
+
+        repository.rugged
+      end
+    end
+  end
+
   describe "#discover_default_branch" do
     let(:master) { 'master' }
     let(:feature) { 'feature' }