Greptile Summary

This PR removes the explicit platform parameter from rebase_prebuilt_stack_image_paths and its helpers, instead extracting the platform segment directly from the artifact path itself. This allows multi-platform prebuilt releases to correctly locate shared artifacts that were built under a different platform directory.

• artifact_location_from_build_path now returns (platform, artifact_dir) extracted from the .alien/build/<platform>/<artifact> path pattern, replacing the old artifact_dir_from_build_path that required the caller-supplied platform to match the path's platform component.
• The rebased path is constructed using the platform embedded in the artifact path rather than the current release's target platform, enabling a gcp release to use an artifact that lives under build/aws/.
• A new test rebase_prebuilt_stack_image_paths_rewrites_cross_platform_artifact_path is added alongside a minor refactor of the existing same-platform test.

Confidence Score: 4/5

Safe to merge; the logic change is small, well-scoped, and the happy path is covered by tests.

The refactored artifact_location_from_build_path correctly extracts the platform segment from the artifact path itself rather than requiring the caller to supply it, which is the right approach for cross-platform sharing. The only notable gap is that the new test doesn't actually exercise the cross-platform case — it creates an artifact whose path and destination directory use the same platform, so it doesn't prove the function works when the artifact's platform differs from the release's target platform. The core logic is simple enough that this is low risk in practice, but a regressor in the path-parsing could go undetected.

crates/alien-cli/src/commands/release.rs — specifically the new test at line 1614 which doesn't fully validate the cross-platform scenario it claims to cover.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["release_task_core(platform=gcp, --prebuilt)"] --> B["rebase_prebuilt_stack_image_paths(stack, output_dir)"]
    B --> C["for each Worker / Container / Daemon"]
    C --> D["rebase_prebuilt_image_path(resource_type, id, image, output_dir)"]
    D --> E{"image_path.exists()?"}
    E -- yes --> F["return Ok(None)"]
    E -- no --> G["artifact_location_from_build_path(image_path)"]
    G --> H{"path contains .alien/build/p/a?"}
    H -- yes --> J["extract (artifact_platform, artifact_dir)"]
    J --> K["rebased = output_dir/build/{artifact_platform}/{artifact_dir}"]
    K --> L{"rebased exists && is_dir?"}
    L -- yes --> M["return Ok(Some(rebased))"]
    L -- no --> N["return Err(ValidationError)"]
    H -- no --> I{"absolute or relative path?"}
    I -- yes --> O["return Err(ValidationError)"]
    I -- no --> P["return Ok(None) — remote URI"]

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
crates/alien-cli/src/commands/release.rs:1614-1637
**Test doesn't demonstrate the new cross-platform behaviour**

The new test and the existing `rebase_prebuilt_stack_image_paths_rewrites_copied_artifact_path` are structurally identical: both set up an artifact whose path and on-disk location use the same platform (`gcp`/`aws` respectively). The distinguishing claim — that a release targeting one platform correctly reuses an artifact built under a different platform — is invisible here because `platform` is no longer passed in at all. A more informative test would create an artifact under `aws/` while naming the resource in a way that makes it clear the release context is `gcp`. As written, if `artifact_location_from_build_path` were accidentally reverted to require `window[2] == "aws"`, this test would still pass.

_{Reviews (1): Last reviewed commit: "chore: format files checked by ci" | Re-trigger Greptile}