Squash fails due to "Sparse checkout leaves no entry on working directory"

https://gitlab.com/gitlab-org/gitlab-ee/issues/4960#note_59416224 failed not due to encoding issues but to:

Sparse checkout leaves no entry on working directory

From: https://log.gitlap.com/goto/cbcde22a7f3c6d0a46bd402caba435d5

/cc: @smcgivern