fix: resolve issue around copying root

[aaron-prindle]

Changes taken from @kvaps PR here: #1724. Re-submitting here as that PR required rebasing and was no longer active there. Original description added below:

Fixes #960

Description

This PR updates otiai10/copy module from v1.0.2 to v1.6.0.
Adds option to not copying ignored paths for CopyFileOrSymlink which solves two problems at once:

• Allows copying root (/)
• Avoid leaking docker credentials using COPY command while building the image.

It might need rebase after merging #1725.
This branch includes both fixes: kvaps:fix-copying-root-and-ownership; compiled docker images:

ghcr.io/kvaps/kaniko-executor:v1.6.0-fix
ghcr.io/kvaps/kaniko-executor:v1.6.0-fix-debug
ghcr.io/kvaps/kaniko-warmer:v1.6.0-fix

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• Includes unit tests
• Adds integration tests if needed.

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Reviewer Notes

• The code flow looks good.
• Unit tests and or integration tests added.

Release Notes

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

- Add additional check for ignored files on COPY
- Support copying root (`/`) of image

Additional ideas here related to this:
#960 (comment)

[lc-guy]

This branch still has issues for me.

Without the fix:

INFO[0166] Saving file . for later use                  
error building image: could not save file: copying file: read /dev/autofs: invalid argument

With the fix:

INFO[0159] Saving file . for later use                  
error building image: could not save file: copying ownership: chown /kaniko/0/__cacert_entrypoint.sh: no such file or directory

[lc-guy]

Now that #2863 has been merged, the above issue with files in /kaniko has been fixed. Would it be possible to look into merging this (@aaron-prindle)?

[dobicinaitis]

I just encountered the same issue with multi-stage builds that use layer squashing via the COPY --from=final / / method.
Was pleased to find that there's already a fix for this, but it appears that the PR has become inactive. @aaron-prindle is there a possibility that the changes could be rebased and merged for the next release?