fix(spi-transfer): ExportResult.END carried ResultType.CONTINUE

[alexeyqu]

Summary

ExportResult exposes two convenience constants. The second one is wrong:

public static final ExportResult CONTINUE = new ExportResult(ResultType.CONTINUE);
public static final ExportResult END = new ExportResult(ResultType.CONTINUE);  // <-- END, built with CONTINUE

One character: END now carries ResultType.END.

Why it matters, and why it doesn't (yet)

The constant has no call sites anywhere in the repo — every exporter constructs new ExportResult<>(ResultType.END, ...) directly — so this is latent, not a live bug. Nothing changes for existing code.

It is worth fixing anyway because it is the obvious thing for a new exporter to reach for, and the resulting failure is quiet rather than loud. PortabilityInMemoryDataCopier#copyHelper terminates on continuationData == null, not on ResultType:

ContinuationData continuationData = exportResult.getContinuationData();
if (null != continuationData) { ... recurse ... }

So an exporter returning ExportResult.END would not spin — the constant also carries null exportedData, and copyIteration skips the import entirely when that is null. The job would run to COMPLETE having imported nothing at all. That is a much harder thing to notice than a hang.

I hit this while writing an exporter for the offline-demo module (#1509) and worked around it there by using the enum directly. Splitting the fix out so it lands as a fix: in its own right rather than being buried in a feat: — this repo squash-merges, so the PR title is what commitizen sees.

Test plan

• docker compose run --rm test --no-daemon build — full repo compiles and tests pass
• grep -rn "ExportResult.END" --include=*.java . — confirms the constant has no consumers, so no behaviour changes for existing callers

Note for downstream consumers

portability-spi-transfer is published to Maven Central. Any external caller relying on the current value of ExportResult.END would be relying on it reporting CONTINUE, which is a bug rather than a contract — but it is a behaviour change for them, so it is worth a line in the release notes.

[alexeyqu]

Surprisingly, this typo existed since Jan 22, 2018 #29 cc @lisad 😮