Merge branch 'jc/do-not-let-random-file-interfere-with-completion-tests' into maint

Scripts to test bash completion was inherently flaky as it was
affected by whatever random things the user may have on $PATH.

* jc/do-not-let-random-file-interfere-with-completion-tests:
  t9902: protect test from stray build artifacts

diff --cc contrib/completion/git-completion.bash
Simple merge