Make the README mksync check runnable on macOS - #390
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The check normalised both sides with `sed -z '$s/\n*$//'` before diffing.
`-z` is a GNU extension. BSD sed, which is what macOS ships, rejects it:
sed: illegal option -- z
Because the flag failed on *both* sides of the diff, the step compared two
empty streams and exited 0. On a Mac it did not merely fail to work, it
reported success on a README that was actually stale, so a contributor
checking locally before pushing got a green result and a red CI.
`$(...)` already strips every trailing newline, and `printf '%s\n'` puts
exactly one back, so the same normalisation happens with no GNU-only flag and
the readable `diff -u` output is kept.
Verified on macOS: the new command exits 0 on the current README, and exits 1
with the expected one-line table-of-contents diff once a heading is added
without regenerating. The old command exits 0 in both cases.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Summary
The README check normalises both sides before diffing:
-zis a GNU extension. BSD sed, which is what macOS ships, rejects it:Because the flag fails on both sides,
diffends up comparing two empty streams and the command exits 0. On a Mac it does not merely fail to work: it reports success on a README that is actually stale. A contributor who runs the check locally before pushing gets a green result and then a red CI, which is a confusing way to lose half an hour. That is exactly what happened to me on #382.Fix
$(...)already strips every trailing newline, andprintf '%s\n'puts exactly one back, so the normalisation is identical with no GNU-only flag. Thediff -uoutput on failure is unchanged.Verified on macOS
I also parsed the workflow YAML, extracted the
run:string, and executed it verbatim to confirm both outcomes, rather than testing a hand-retyped approximation of it.CI on Linux is unaffected, since both forms normalise the same way there.