Make squashing optional

[picsel2]

Description

This PR adds an imput parameter "squash" allowing optional layer squashing when building from scratch.

Related Issue(s)

Closes #138

Checklist

• This PR includes a documentation change
• This PR does not need a documentation change

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• This PR includes test changes
• This PR's changes are already tested

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• This change is not user-facing
• This change is a patch change
• This change is a minor change
• This change is a major (breaking) change

Changes made

• Introduction of input argument squash (defaulting to true)
• Set --squash argument conditionally for the buildah config command line

[bcrochet]

This to me is a bad default for this option. A default like this should mimic the existing behavior, and not a new behavior.

[picsel2]

I am a bit confused here. The existing behaviour (at least when I opened this PR) is to squash all layers, see #138

[bcrochet]

I see your point. That is indeed the existing behavior.

I would argue then that not squashing is a better default in general. :)