Add support for Containerfile

[bshephar]

This change adds a function to check for either a Dockerfile or Containerfile. If either exist, and the user hasn't explicitly provided the file to use, then we can default to the existing file.

Fixes #99

[bshephar]

First time working with Swift, be gentle. :)
I've left this on draft while I try to get the tests working locally.

[bshephar]

Removing this because the validation is happening in the new checkForDockerOrContainerfile() function. But maybe there is a more clean way to keep all of the validation happening here. Happy to take suggestions on that.

[amatzen]

For readability and responsibility determination, I would try to keep validation logic in the validate() function.

Perhaps by moving the defaultBuildFileNames constant from run() to a static attribute, and creating a fun checkBuildFileIsPresent(atPath: String) -> Bool that determines the file is present.

[bshephar]

Yeah, I agree. It would be much nicer to keep it here. I'll keep thinking about this one while we debate the merits of just switching the default to Containerfile over on the linked issue:
#99

[bshephar]

Ok, this builds and when I test the binary locally, it works to fix the issue I raised:

Testing on:

❯ sw_vers
ProductName:            macOS
ProductVersion:         26.0
BuildVersion:           25A5279m

Implicit Containerfile

❯ ./container build -t fedora:test .
Using Containerfile at: /Users/brendanshephard/Code/okd/fedora-work/Containerfile
[+] Building 5.7s (5/5) FINISHED
 => [resolver] fetching image...docker.io/library/fedora:latest                                                                                                                                                                                         0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                       0.0s
 => => transferring context: 2B                                                                                                                                                                                                                         0.0s
 => oci-layout://docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                0.0s
 => => resolve docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                  0.0s
 => CACHED [linux/arm64 1/2] RUN dnf in pre-commit zsh ripgrep g++ mtr openssh openssh-clients tmux neovim fzf git make gcc go rust nodejs unzip python3-pip -y  && useradd nvim  && useradd -s /usr/bin/zsh -G wheel bshephar                          0.0s
 => exporting to oci image format                                                                                                                                                                                                                       3.3s
 => => exporting layers                                                                                                                                                                                                                                 0.0s
 => => exporting manifest sha256:55e631e502e70ecf8e667b668d144e34951173fa3a2fb2534369e6d1390fe37f                                                                                                                                                       0.0s
 => => exporting config sha256:83a72694cf59b06bf33448a43935332ecca8dd3af17ac28d74ae26fcdca84408                                                                                                                                                         0.0s
 => => exporting manifest list sha256:e5ead77aaf12559ba34defdb6f1d7429431c8febc1daed40d564e78f67bb24a0                                                                                                                                                  0.0s
 => => sending tarball                                                                                                                                                                                                                                  3.3s
Successfully built fedora:test

Bad file:

❯ ./container build -t fedora:test -f blahfile
Error: Provided container build file does not exist: blahfile

Explicit Containerfile:

❯ ./container build -t fedora:test -f Containerfile
Using Containerfile at: /Users/brendanshephard/Code/okd/fedora-work/Containerfile
[+] Building 5.6s (5/5) FINISHED
 => [resolver] fetching image...docker.io/library/fedora:latest                                                                                                                                                                                         0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                       0.0s
 => => transferring context: 2B                                                                                                                                                                                                                         0.0s
 => oci-layout://docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                0.0s
 => => resolve docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                  0.0s
 => CACHED [linux/arm64 1/2] RUN dnf in pre-commit zsh ripgrep g++ mtr openssh openssh-clients tmux neovim fzf git make gcc go rust nodejs unzip python3-pip -y  && useradd nvim  && useradd -s /usr/bin/zsh -G wheel bshephar                          0.0s
 => exporting to oci image format                                                                                                                                                                                                                       3.3s
 => => exporting layers                                                                                                                                                                                                                                 0.0s
 => => exporting manifest sha256:55e631e502e70ecf8e667b668d144e34951173fa3a2fb2534369e6d1390fe37f                                                                                                                                                       0.0s
 => => exporting config sha256:83a72694cf59b06bf33448a43935332ecca8dd3af17ac28d74ae26fcdca84408                                                                                                                                                         0.0s
 => => exporting manifest list sha256:e5ead77aaf12559ba34defdb6f1d7429431c8febc1daed40d564e78f67bb24a0                                                                                                                                                  0.0s
 => => sending tarball                                                                                                                                                                                                                                  3.3s
Successfully built fedora:test

Explicit Dockerfile:

❯ ./container build -t fedora:test -f Dockerfile
Using Dockerfile at: /Users/brendanshephard/Code/okd/fedora-work/Dockerfile
[+] Building 6.0s (5/5) FINISHED
 => [resolver] fetching image...docker.io/library/fedora:latest                                                                                                                                                                                         0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                       0.0s
 => => transferring context: 2B                                                                                                                                                                                                                         0.0s
 => oci-layout://docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                0.0s
 => => resolve docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                  0.0s
 => CACHED [linux/arm64 1/2] RUN dnf in pre-commit zsh ripgrep g++ mtr openssh openssh-clients tmux neovim fzf git make gcc go rust nodejs unzip python3-pip -y  && useradd nvim  && useradd -s /usr/bin/zsh -G wheel bshephar                          0.0s
 => exporting to oci image format                                                                                                                                                                                                                       3.8s
 => => exporting layers                                                                                                                                                                                                                                 0.0s
 => => exporting manifest sha256:55e631e502e70ecf8e667b668d144e34951173fa3a2fb2534369e6d1390fe37f                                                                                                                                                       0.0s
 => => exporting config sha256:83a72694cf59b06bf33448a43935332ecca8dd3af17ac28d74ae26fcdca84408                                                                                                                                                         0.0s
 => => exporting manifest list sha256:e5ead77aaf12559ba34defdb6f1d7429431c8febc1daed40d564e78f67bb24a0                                                                                                                                                  0.0s
 => => sending tarball                                                                                                                                                                                                                                  3.8s
Successfully built fedora:test

Implicit Dockerfile:

❯ ./container build -t fedora:test
Using Dockerfile at: /Users/brendanshephard/Code/okd/fedora-work/Dockerfile
[+] Building 5.3s (5/5) FINISHED
 => [resolver] fetching image...docker.io/library/fedora:latest                                                                                                                                                                                         0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                       0.0s
 => => transferring context: 2B                                                                                                                                                                                                                         0.0s
 => oci-layout://docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                0.0s
 => => resolve docker.io/library/fedora:latest@sha256:16ca3e34a9545583551589e71882f1f27cbce3c2f1fc6210c932d22a6931b73b                                                                                                                                  0.0s
 => CACHED [linux/arm64 1/2] RUN dnf in pre-commit zsh ripgrep g++ mtr openssh openssh-clients tmux neovim fzf git make gcc go rust nodejs unzip python3-pip -y  && useradd nvim  && useradd -s /usr/bin/zsh -G wheel bshephar                          0.0s
 => exporting to oci image format                                                                                                                                                                                                                       3.2s
 => => exporting layers                                                                                                                                                                                                                                 0.0s
 => => exporting manifest sha256:55e631e502e70ecf8e667b668d144e34951173fa3a2fb2534369e6d1390fe37f                                                                                                                                                       0.0s
 => => exporting config sha256:83a72694cf59b06bf33448a43935332ecca8dd3af17ac28d74ae26fcdca84408                                                                                                                                                         0.0s
 => => exporting manifest list sha256:e5ead77aaf12559ba34defdb6f1d7429431c8febc1daed40d564e78f67bb24a0                                                                                                                                                  0.0s
 => => sending tarball                                                                                                                                                                                                                                  3.2s
Successfully built fedora:test

[amatzen]

I agree with your point that Container CLI should have support for Containerfiles.

I've made some code-related suggestions, but I do think the CLI should default to generic terminology (e.g. Containerfile) and use vendor-specific Dockerfile as a synonym – not vice-versa.

[amatzen]

For readability and responsibility determination, I would try to keep validation logic in the validate() function.

Perhaps by moving the defaultBuildFileNames constant from run() to a static attribute, and creating a fun checkBuildFileIsPresent(atPath: String) -> Bool that determines the file is present.

[wlan0]

Thanks for submitting this PR!

Before proceeding with code review, let’s first discuss and align on the proposed direction. Please contribute your thoughts to the discussion here: #99

Once we’ve reached consensus there, we’ll revisit this PR. Appreciate your cooperation!

[bshephar]

I agree with your point that Container CLI should have support for Containerfiles.

I've made some code-related suggestions, but I do think the CLI should default to generic terminology (e.g. Containerfile) and use vendor-specific Dockerfile as a synonym – not vice-versa.

Yeah, I think before we push too much further into the PR, it would be nice to understand if the maintainers are open to using Containerfile as the default. If that's the case, we can vastly simplify all of this and just change the default:
https://github.com/apple/container/blob/main/Sources/CLI/BuildCommand.swift#L57

But yeah, if not, I think it would be great to support both at least. Since Dockerfile is very specific to the company "Docker".