Re: [PATCH v3 0/3] t/lib-httpd: make CGI test helpers concurrency-safe

>  * Patch 1 fixes apply-one-time-script.sh (the actual flake) and adds t5567,
>    which drives the helper directly with no web server so the overlap can be
>    forced deterministically.
>  * Patch 2 makes http-429.sh atomic.
>  * Patch 3 documents the atomic idioms next to where t/lib-httpd.sh installs
>    the CGI scripts, so the guidance is in front of anyone adding another
>    helper.
>
> Changes since v2:
>
>  * Patch 1 now consumes the marker with a plain "rm" (without "-f") instead
>    of a rename. "rm" without "-f" already fails once the marker is gone,
>    which is the atomicity the helper needs. A new comment explains why the
>    helper discards the one-time script's stderr: a losing request can find
>    the marker already removed.
>
>  * Patch 3 is now specific to the lib-httpd CGI helpers and lives beside
>    their install site in t/lib-httpd.sh, rather than as a general section in
>    t/README.
>
>  * Reworded several helper comments and the patch 1 and 2 log messages for
>    clarity and to match the code; no behavior change.