Add container copy/cp command for host-container file transfer

[simone-panico]

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Motivation and Context

Closes #232.

Adds the container copy (aliased as cp) command to copy files between a running container and the local filesystem.

I saw #1023 and the feedback from @dcantah — the previous attempt relied on tar being installed inside the container.
This implementation takes the recommended approach:
file transfers go through the guest agent via the existing copyIn/copyOut methods on the core Containerization, with no dependency on container tooling.

Testing

• Tested locally
• Added/updated tests
• Added/updated docs

[JaewonHur]

Related to #232

[JaewonHur]

⏺ CopyOut/CopyIn Scenarios: Current vs Docker Behavior

Scenario 1: copy(in/out) src dst (src must exist)

• File, Directory → Non-existing:

  • Docker (desired): save as dst
  • Current: File is saved as dst, Directory is not supported.

• File → File

  • Docker (desired): replace dst
  • Current: replace dst

• Directory → File

  • Docker (desired): error
  • Current: Directory is not supported

• File, Directory → Directory

  • Docker (desired): save under dst
  • Current: File returns error, Directory is not supported.

Scenario 2: copy(in/out) src dst/ (dst must be a directory if existing)

• File → Non-existing:

  • Docker (desired): error no such directory
  • Current: dst is created and src file is saved under dst.

• Directory → Non-existing:

  • Docker (desired): save as dst
  • Current: Directory is not supported.

• File, Directory → Directory

  • Docker (desired): save under dst
  • Current: File is saved under dst. Directory is not supported.

Scenario 3: copy(in/out) src/ dst (src must be an existing directory)

• Directory → Non-existing:

  • Docker (desired): save as dst
  • Current: Directory is not supported.

• Directory → File

  • Docker (desired): error
  • Current: Directory is not supported.

• Directory → Directory

  • Docker (desired): save under dst
  • Current: Directory is not supported.

Scenario 4: copy(in/out) src/ dst/ (src must be an existing directory & dst must be a directory if existing)

• Directory → Non-existing:

  • Docker (desired): save as dst
  • Current: Directory is not supported.

• Directory → Directory

  • Docker (desired): save under dst
  • Current: Directory is not supported.

[JaewonHur]

Hi @simone-panico
Above I summarized the desired behavior and current behavior.

The bold italic phrases are what is different from desired behavior (i.e., docker) now, and can be addressed.

Below is general comments.

1. Copying directory is not supported yet, we need to handle it later.
2. If dst/, it would be better to check in command line if dst is directory if it exists.

[JaewonHur]

Hi @simone-panico
Could you try this PR with apple/containerization#474, which supports copying directories.

You may need to build this project with local containerization (BUILDING.md), and wire up SandboxService.

[dcantah]

@JaewonHur the change above does not allow copying directories. It adds a tar reader/writer that will be used to support this, but it's not in the change itself.

[simone-panico]

If you’re interested, I could try to create a Directory Copier within containerization. It would also be a great challenge for me

[simone-panico]

Hey @JaewonHur
No worries, and thank you for the Stat RPC. I've started looking into it but haven't finished yet. I'll get to it as soon as I can 😄

[JaewonHur]

@simone-panico Thank you!
You might want to change copyIn and copyOut methods of LinuxContianer in containerization to use stat RPC.

[simone-panico]

Hey @JaewonHur, sorry this took so long. I had to finish my finals.
I’ve now implemented the Stat RPC in apple/containerization#727 and updated this PR to use it for copyIn.
Every copy test is passing now: 70/70. 😄

[JaewonHur]

@simone-panico Not at all :) I really appreciate for all your hard work!

[JaewonHur]

@simone-panico Could you do make fmt and push again.

Once the containerization PR is merged, we should bump that in Package.swift, and able to merge this PR.

[simone-panico]

This one also doesn't seem to be signed correctly. Could you please sign this as well?

Should be correct now, right?

[JaewonHur]

Yes. Looks good.

[github-actions]

Code Coverage

Tier	Line Coverage
Unit	33.64%
Integration	19.94%
Combined	53.01%

[JaewonHur]

Hi! I tagged latest containerization to 0.32.2.

Here could you update scVersion in Package.swift to 0.32.2, then swift package update containerization?

The Package.resolved file should have only the containerization package updated (and the originHash at the top).

[JaewonHur]

@simone-panico Finally merged :) Thank you so much for your hard work and patience!

[jglogan]

@simone-panico Definitely, thanks for the patience and the effort you've put in. It's nice to have this feature in place!