[rudycelekli]

What's wrong

updater-design.md §16 says:

Artifacts are reproducible. Fixed mtimes in the tar mean the same inputs produce the same archive, so a rebuild can be compared against what shipped; a test asserts two packages of the same inputs hash identically.

xtask package fixes the mtime, but it appends bin/* in std::fs::read_dir order, and that order belongs to the filesystem. On ext4 (the CI runners) it is htree hash order, seeded per filesystem, so the same staged binaries packed on two runners can produce two archives with two different sha256s. The name list written into version.toml was already sorted. The archive order was not. Also, no test in xtask/tests packs the same inputs twice, so the test the design doc mentions does not exist.

Here is what packing eight stub binaries on main produced on APFS:

left:  ["bin/btd", "bin/zeta", "bin/updaterd", "bin/configd", "bin/robotd", "bin/mid", "bin/alpha", "bin/nfcd"]
right: ["bin/alpha", "bin/btd", "bin/configd", "bin/mid", "bin/nfcd", "bin/robotd", "bin/updaterd", "bin/zeta"]

The fix

package collects the bin_dir paths, sorts them, and then appends them. shipped is built in that order, so the separate shipped.sort() is no longer needed. --include entries keep their command-line order, which the workflow already fixes.

Test

binaries_are_packaged_in_a_fixed_order (in xtask/tests/artifact.rs) runs the real xtask package on eight stub binaries. It checks that the bin/ entries in the archive are in sorted order, and that packing the same files created in reverse order gives byte-identical archives. The order assertion is the one that catches the bug. Two directories on one filesystem usually enumerate the same way, so the byte comparison alone would pass on main. The test comment says this.

• On main: fails with the order shown above.
• With the fix: passes.
• Mutation check: I restored xtask/src/main.rs from origin/main and the named test failed. Then I put the fix back.

Checks (macOS, aarch64)

• cargo test -p xtask: 68 passed, 0 failed (41 + 6 + 18 + 3)
• cargo clippy -p xtask --all-targets -- -D warnings: clean
• cargo fmt -p xtask --check: clean

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