Add error code to project export command status log

If the tar command fails without any output, it would be useful to
have the error code. This commit adds the status code to the message.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/351155

Changelog: changed

lib/gitlab/import_export/command_line_util.rb

@@ -81,12 +81,16 @@ module Gitlab
 
         return true if status == 0
 
+        output = output&.strip
+        message = "command exited with error code #{status}"
+        message += ": #{output}" if output.present?
+
         if @shared.respond_to?(:error)
-          @shared.error(Gitlab::ImportExport::Error.new(output.to_s))
+          @shared.error(Gitlab::ImportExport::Error.new(message))
 
           false
         else
-          raise Gitlab::ImportExport::Error, 'System call failed'
+          raise Gitlab::ImportExport::Error, message
         end
       end
       # rubocop:enable Gitlab/ModuleWithInstanceVariables

spec/lib/gitlab/import_export/command_line_util_spec.rb

@@ -97,7 +97,7 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil do
           include Gitlab::ImportExport::CommandLineUtil
         end.new
 
-        expect { klass.tar_cf(archive: 'test', dir: 'test') }.to raise_error(Gitlab::ImportExport::Error, 'System call failed')
+        expect { klass.tar_cf(archive: 'test', dir: 'test') }.to raise_error(Gitlab::ImportExport::Error, 'command exited with error code 1: Error')
       end
     end
   end
@@ -125,14 +125,31 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil do
     end
 
     context 'when something goes wrong' do
-      it 'raises an error' do
+      before do
         expect(Gitlab::Popen).to receive(:popen).and_return(['Error', 1])
+      end
 
+      it 'raises an error' do
         klass = Class.new do
           include Gitlab::ImportExport::CommandLineUtil
         end.new
 
-        expect { klass.untar_xf(archive: 'test', dir: 'test') }.to raise_error(Gitlab::ImportExport::Error, 'System call failed')
+        expect { klass.untar_xf(archive: 'test', dir: 'test') }.to raise_error(Gitlab::ImportExport::Error, 'command exited with error code 1: Error')
+      end
+
+      it 'returns false and includes error status' do
+        klass = Class.new do
+          include Gitlab::ImportExport::CommandLineUtil
+
+          attr_accessor :shared
+
+          def initialize
+            @shared = Gitlab::ImportExport::Shared.new(nil)
+          end
+        end.new
+
+        expect(klass.tar_czf(archive: 'test', dir: 'test')).to eq(false)
+        expect(klass.shared.errors).to eq(['command exited with error code 1: Error'])
       end
     end
   end