[zzwong]

Summary

Fix directory overrides in the Linux RPM helper without changing the package spec or release workflow.

• Resolve output, staging and build directories once. Absolute RPM_TOPDIR and DIFFZ_DIST values no longer get an extra checkout prefix in RPM macros.
• Create the output directory when the build directory is separate.
• Preserve quoted shell arguments and propagate output-copy failures instead of printing success.
• Add ten regressions to the existing RPM test file, already run by CI.

Reproduction

Baseline: Diffz 0.4.0 source at 7b68d0b6959607ff094745f8ab28a123ef2de2a8; local checks ran on Linux x86_64.

With an existing staged tree, invoke the helper with an absolute RPM_TOPDIR, or an absolute DIFFZ_DIST and the default build directory. The helper copies the payload to the chosen directory but previously passed $PWD/$top/SOURCES to rpmbuild. Expected: the declared RPM source directory is the directory containing the copied payload.

A separate relative build directory also left a new output directory uncreated. The old find -exec cp ... \\; ignored copy failures and could print a success message without a collected package.

Validation

• python3 -B scripts/tests/test_smoke_linux_rpm.py -v: 33 passed (23 existing checks and ten new regressions).
• The same final tests against the unchanged helper: four assertion failures and two missing-output errors, demonstrating regression sensitivity.
• Bash syntax, Python parsing, patch applicability and whitespace checks passed.
• Verified the source files against GitHub blob hashes and the final remote tree as an exact two-file change.

These fixtures execute the actual Bash helper with real temporary filesystem operations and a recording rpmbuild shim. The shim emits a synthetic marker, not an RPM. They cover defaults, relative/absolute overrides, shell argument boundaries, stage preservation, missing staging, packager failure and collection failure.

Remaining qualification

scripts/check.sh core and scripts/check.sh native both stopped at the Cargo preflight with exit 127. Cargo/Rust, rpmbuild, ShellCheck and actionlint are unavailable locally. No tools were installed.

Real Fedora RPM creation and clean-runtime installation, Rust tests/Clippy/audit, macOS checks and hosted CI remain unrun at submission. The unchanged spec's native handling of paths with spaces is not qualified by the shell/shim tests. This remains a draft pending the existing CI and Fedora packaging gates.

No application source, RPM dependency declarations, workflow permissions, release configuration or cache policy changed.