rechunker: Use open_image when transport is oci-archive

[ckyrouac]

This allows the use of oci-archive when the archive doesn't yet exist.

fixes #5442

[gemini-code-assist]

Code Review

This pull request modifies the logic for checking existing OCI images to better handle the oci-archive transport, especially when the archive file doesn't exist. The change uses proxy.open_image instead of proxy.open_image_optional for this transport. A new test case is added to test.sh to verify this functionality. The review suggests improving error handling in the Rust code and ensuring test hygiene in the shell script.

[gemini-code-assist]

Using .ok() here swallows errors from proxy.open_image().await, treating any failure as if the image does not exist. This could mask underlying issues such as permissions errors or invalid paths, leading to unexpected behavior.

It would be more robust to handle only the "not found" case as a non-error condition and propagate other errors. At a minimum, logging the discarded error at a debug level would aid in troubleshooting potential issues in the future.

            let img = if transport == OCI_ARCHIVE_TRANSPORT {
                match proxy.open_image(output).await {
                    Ok(img) => Some(img),
                    Err(e) => {
                        tracing::debug!("Ignoring error opening oci-archive: {e}");
                        None
                    }
                }
            } else {
                proxy.open_image_optional(output).await?
            };

[cgwalters]

We can do this as a followup

[cgwalters]

I wrote a helper for this bootc-dev/bootc#1464

[cgwalters]

/override ci/prow/fcos-e2e

[openshift-ci]

@cgwalters: Overrode contexts on behalf of cgwalters: ci/prow/fcos-e2e

In response to this:

/override ci/prow/fcos-e2e

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