store gpg return directory locally

lib/gitlab/gpg.rb

@@ -44,19 +44,23 @@ module Gitlab
 
     def using_tmp_keychain
       Dir.mktmpdir do |dir|
-        @original_dirs ||= [GPGME::Engine.dirinfo('homedir')]
-        @original_dirs.push(dir)
+        previous_dir = current_home_dir
 
         GPGME::Engine.home_dir = dir
 
         return_value = yield
 
-        @original_dirs.pop
-
-        GPGME::Engine.home_dir = @original_dirs[-1]
+        GPGME::Engine.home_dir = previous_dir
 
         return_value
       end
     end
+
+    # 1. Returns the custom home directory if one has been set by calling
+    #    `GPGME::Engine.home_dir=`
+    # 2. Returns the default home directory otherwise
+    def current_home_dir
+      GPGME::Engine.info.first.home_dir || GPGME::Engine.dirinfo('homedir')
+    end
   end
 end

spec/lib/gitlab/gpg_spec.rb

@@ -43,6 +43,28 @@ describe Gitlab::Gpg do
       ).to eq []
     end
   end
+
+  describe '.current_home_dir' do
+    let(:default_home_dir) { GPGME::Engine.dirinfo('homedir') }
+
+    it 'returns the default value when no explicit home dir has been set' do
+      expect(described_class.current_home_dir).to eq default_home_dir
+    end
+
+    it 'returns the explicitely set home dir' do
+      GPGME::Engine.home_dir = '/tmp/gpg'
+
+      expect(described_class.current_home_dir).to eq '/tmp/gpg'
+
+      GPGME::Engine.home_dir = GPGME::Engine.dirinfo('homedir')
+    end
+
+    it 'returns the default value when explicitely setting the home dir to nil' do
+      GPGME::Engine.home_dir = nil
+
+      expect(described_class.current_home_dir).to eq default_home_dir
+    end
+  end
 end
 
 describe Gitlab::Gpg::CurrentKeyChain do