Re: [PATCH v2 0/3] t/lib-httpd: make CGI test helpers concurrency-safe

"Michael Montalbo via GitGitGadget" [off-list ref] writes:

Each fix is local: claim/consume the one-shot marker with an atomic rename,
and elect the first request with an atomic mkdir, rather than a "test -f"
followed by a separate remove or touch.

 * 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 generally in t/README (they are not
   specific to CGI or HTTP), citing Git's own lockfile machinery and
   make_symlink(), with a pointer from the lib-httpd list.

I was scanning the "What's cooking" report for topics marked as
"Needs review" to see if I could find ones that are relatively easy
to validate, and I hit this one.

The key change [1/3] is well thought out and nicely done.  [2/3] is
explained better than the corresponding step in v1, and [3/3] adds
helpful tips to the t/README documentation.  They all look quite
good.

Thanks.