copier: RemoveAll possibly-directories

[nalind]

What type of PR is this?

/kind bug

What this PR does / why we need it:

When we attempt to remove a directory to make way for a non-directory as part of extracting content, use RemoveAll() instead of Remove().

How to verify it

Added to a unit test!

Which issue(s) this PR fixes:

Fixes #3655

Special notes for your reviewer:

Does this PR introduce a user-facing change?

None

[rhatdan]

LGTM
@flouthoc @giuseppe @vrothberg @umohnani8 @TomSweeneyRedHat PTAL

[flouthoc]

LGTM

[giuseppe]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: flouthoc, giuseppe, nalind

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[vrothberg]

Thanks, Nalin! That got me further but COPY --from=fedora / / is now failing with:

[...] error creating "/var/spool/mail": stat /var/spool/mail: too many levels of symbolic link

[nalind]

I can't reproduce that here with the Dockerfile from #3655. What's the digest of the fedora image you're copying from? Perhaps it's different from the latest I just pulled on amd64?

[vrothberg]

Apologies, I used a braindump with another base image. It works with busybox but fails with alpine:

from alpine           
copy --from=fedora / /