155: snapshotting preserves atime

[mzihlmann]

Fixes #155

Description

Unfortunately can't finish it on my side alone, everytime os.Open gets called we run into this issue. I don't see a way how i can monkeypatch it in go, so the only solution is to bring all dependencies to expose os as an interface, that will take some time.

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Describe any changes here so maintainer can include it in the release notes, or delete this block.

Examples of user facing changes:
- kaniko adds a new flag `--registry-repo` to override registry

[mzihlmann]

oh! buildkit doesnt preserve atime accross copy --from? let's have a look what the standard says.

[mzihlmann]

hmmm can't find reference to it, but it sort of make sense. snapshotting itself shouldnt alter atime, but if you create a copy its fine. let me check whether I can implement that behaviour here

[mzihlmann]

we can assume we have CAP_FOWNER, as per GoogleContainerTools/kaniko#778 (comment), so this feature should not break customer's setups and can be released without feature-flags. but it would be good to make this more explicit longterm.