It rewrites a tracked file and restores it byte-for-byte — but the restore
bumped the mtime, and in this repo that is not cosmetic. The repo IS the
deployment root and nothing takes effect until the service restarts, so 'is
:8090 stale?' is answered by comparing the service's start time against source
mtimes. A tool that moves those without changing a byte makes that check lie:
it reported the live service 16 minutes stale while it was serving current code.
Restores atime/mtime with os.utime, with a test whose defeating change is
dropping that line. Found by using the staleness check for real, not by review.
649 green; 12/12 U7 falsifiers still proved.