fix: Add parent dirs to mtree

[rparme]

Nested files/folders in image layers result in InvalidImage(MissingParentDirectory: Parent directory does not exist for file when deploying on AWS if the parent folders aren't listed in the layer archive mtree.

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Changes are visible to end-users: no

Test plan

• Manually built an image with aws_py_lambda with internal and external dependencies, pushed to ECR and deployed on AWS Lambda. Successfully ran code using internal and external dependencies.
• Successfully built, deploy and tested //examples/python_lambda:tarball
  

• Manual testing; please provide instructions so we can reproduce:

bazel run //examples/python_lambda:tarball
# Then push, deploy and run the image on AWS Lambda

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[hofbi]

Looking at this comment and your the code you are adding, is this something we could simplify by using some rules from https://github.com/bazel-contrib/tar.bzl/blob/main/docs/mtree.md?

[rparme]

What part are you looking to simplify exactly?
The mtree_spec rule simply creates an mtree file for the files passed in srcs, it won't create entries for parent dirs of these files. mtree_mutate has many properties but none that would help either except having a whole different awk_script.

[hofbi]

Didn't look too much into the details. I just saw this comment and would have guessed that this could be implemented already somewhere else. Nevermind.

[alexeagle]

I agree we should try to de-duplicate these if we can.

[rparme]

Sorry I didn't realize this is related to the comment.
What about making _mtree_line public in @tar.bzl//tar:mtree.bzl, similarly to what is done for s3_sync in rules_aws ?

[alexeagle]

Yeah that's the obvious answer. However I suspect there's a somewhat more substantial code sharing possible here, since https://github.com/aspect-build/rules_py/blob/main/py/private/py_image_layer.bzl was created after this rule is sketched out. @thesayyn can confirm - or if you have a few minutes to compare the implementations, maybe it's obvious how to do it.