[ice-zeus]

Summary

native/updater never compiled for Linux: velopack 1.2.161 gates VelopackLocator::get_root_dir to non-Linux targets (src/locator.rs:216), so src/lib.rs:36 failed with E0599. CI-1's new Linux job found this (PR #5).

• A cfg-gated root_dir helper reads the root through get_appimage_path on Linux and get_root_dir everywhere else. On Linux, velopack fills both from RootAppDir (the AppImage path), so the value is unchanged.
• The locator-to-config mapping moves from config() into locator_config(&VelopackLocator) so a unit test can cover it with a constructed locator. config() is unchanged for callers.
• No change to the shifter_updater C ABI, to Cargo.toml or to Cargo.lock. Behaviour on non-Linux targets is unchanged.

Area: update-desktop (native/updater/src/lib.rs only). Size: 38 added and 3 removed lines (about 16 production, the rest test). Boundary: n/a (single-repository project).

Regression

New test config_uses_locator_root checks three things: the config root equals the locator root, the packages directory is <AppImage dir>/.shifter-updates on Linux and <packages>/shifter-verified-v1 elsewhere, and config() fails closed for an unpackaged binary.

• Before the fix (origin/main 3bb32ae, Linux, Rust 1.99.0): cargo fmt --check 0; cargo clippy --locked --all-targets -- -D warnings 101 and cargo test --locked 101, both with error[E0599]: no method named get_root_dir found for struct VelopackLocator at src/lib.rs:36.
• After the fix (86f6fe2): see Validation.

Validation (head 86f6fe2)

• Linux (disposable Ubuntu 24.04 c-4, Rust 1.99.0): cargo fmt --check 0, cargo clippy --locked --all-targets -- -D warnings 0, cargo test --locked 2 passed.
• Changed-line coverage on Linux (cargo-llvm-cov 0.9.1): every changed line compiled on Linux is covered, so 100% of the measurable lines. The non-Linux root_dir is compiled out on Linux. It runs in the macOS test but its coverage was not measured.
• macOS (shared pool, mini-one, Rust 1.99.0): fmt, clippy -D warnings and tests (2 passed) all green.
• Windows: not built (no Windows host). The helper uses get_root_dir there, as before.
• git diff --check clean.

Review fixes (head 013e816)

• F1 (non-serious, test-only), fixed in 013e816: on Windows, Velopack replaces an unwritable custom packages directory with one under %LOCALAPPDATA%, so config_uses_locator_root would fail and write into the user profile. The test now creates <tmp>/packages before building the locator. Linux on 013e816 (disposable Ubuntu 24.04 c-4, Rust 1.99.0): cargo fmt --check 0, cargo clippy --locked --all-targets -- -D warnings 0, cargo test --locked 2 passed; cargo-llvm-cov counts the new line. Windows is still not built (no Windows host).

Documentation

No user-facing or API documentation change: the C ABI and documented behaviour are unchanged. The Linux root semantics are documented on the new helper.