exclude .git on stashBack (#4854)

This change allows usage of `stashNoDefaultExcludes` parameter,
as otherwise I think it it impossible to stash back the .git repository.

It should not affect anything if `stashNoDefaultExcludes` is not used.

resources/default_pipeline_environment.yml

@@ -237,7 +237,7 @@ steps:
       workspace: '**/*'
     stashExcludes:
       workspace: 'nohup.out'
-      stashBack: '**/node_modules/**,nohup.out'
+      stashBack: '**/node_modules/**,nohup.out,.git/**'
   dubExecute:
     dockerImage: 'dlang2/dmd-ubuntu:latest'
   githubPublishRelease: