Add descriptive header comments to generated Dockerfiles

[ryanwaite]

Summary

This PR adds informative header comments to all generated Dockerfiles to improve their self-documentation and make them easier to understand for maintainers, security auditors, and users.

Changes

• Added header comment generation to both Alpine and Debian Dockerfile templates
• Headers include package name, ecosystem, version, artifact, and purpose description
• Updated all test cases to expect the new header format
• Feature works across all supported ecosystems (NPM, PyPI, Debian, CratesIO, Maven)

Example Output

Before:

#syntax=docker/dockerfile:1.10
FROM docker.io/library/alpine:3.19
RUN <<'EOF'
# ... build commands

After:

# OSS-Rebuild Dockerfile
# Package: express (npm)
# Version: 4.18.2
# Artifact: express-4.18.2.tgz
# This Dockerfile rebuilds the above package from source for supply chain verification
FROM docker.io/library/alpine:3.19
RUN <<'EOF'
# ... build commands

Benefits

• Should be easy for anyone to immediatley understand what package is being rebuilt
• From an auditing perspective, it's clear what version, artifact, and package we intended to rebuild
• Helps with maintenance and debugging of the generated Dockerfiles

Testing

• All existing test pass
• Updated test cases to handle header generation (this was previously assumed to be empty)
• Manually verified for PyPI and NPM.
• Build succeeded without errors.

[msuozzo]

Overall: I like the self-describing nature of this embedded Dockerfile content and I like the way it's done here.

I suppose I'd first like to understand the context for the change, if any. Do you have a particular circumstance that makes this necessary?

Regardless, thanks for this work!

[ryanwaite]

Overall: I like the self-describing nature of this embedded Dockerfile content and I like the way it's done here.

I suppose I'd first like to understand the context for the change, if any. Do you have a particular circumstance that makes this necessary?

Regardless, thanks for this work!

Thanks for your note. I got a demo of oss-rebuild and I've been thinking about how we might be able to use the project in production environments in a place like Microsoft. I thought about cases where we might be building several versions of a package from source. This could be because teams consuming those packages have pinned to particular versions, etc.

There might be a case where I'm checking these Dockerfiles into a repository and anything that could help them be more self-describing would be helpful, especially because it's hard to read the Dockerfile and intuit how a particular commit hash relates to a specific version of a package. This change was to make it more explicit and hopefully more useful in production environments.

Does that help explain the use case?

[wbxyz]

Agreed, thanks for the contribution! I'm also in favor of self-documenting artifacts.

[wbxyz]

Can the ecosystem be on its own line? Then this description would more clearly match the rebuild.Target type which is the common descriptor across the codebase.

[wbxyz]

Is this description important to include in each dockerfile?

Attempting to capture the project mission sufficiently in the dockerfile comments seems challenging. For example, some people might not be using rebuilds for supply chain verification. Also, just because we generate the dockerfile doesn't mean it works. It's possible the dockerfile will eventually fail to build, so claiming "this file rebuilds ..." might not be accurate.

Instead, WDYT of adding to the OSS-Rebuild line something like this:
"OSS-Rebuild generated build instructions"

And removing the "This Dockerfile line"

[ryanwaite]

Of course, I was putting my intent for how I'd use OSS-rebuild, but that's not everyone's intent. I like the suggestion and removed the "This Dockerfile" line and updated the top comment line as suggested.

[wbxyz]

This looks good to me, but I'd be interested to hear if @msuozzo has any thoughts.

[msuozzo]

this indentation here looks like it differs from the surrounding lines. may be a tabs vs spaces issue.

[ryanwaite]

Oh, that's unfortunate. I've pushed a fix.

[msuozzo]

@wbxyz mentioned the idea that we could use a PURL here which I thought had some nice properties. While a bit less human-readable, we'd get a bit more density and could probably fit the description comfortably into a single comment line.

Given that it'd be a bit more involved to implement, I'd be happy to merge this and to take on the change in a follow-on. What do you think @ryanwaite?

[ryanwaite]

A PURL would have some nice properties. I think it'd be great if you took on that work given how involved it is. If you wanted any feedback, please let me know. I'd be happy to help.