Follow-ups on top of #70888's cherry-picked fix:
- Replace the $((0666 & ~0$u)) shell arithmetic with POSIX who-less
'chmod "=rw"'. zsh (reachable via _find_bash's $SHELL fallback on
bash-less hosts) parses leading-zero constants as decimal and silently
chmods a garbage mode (e.g. 0210); the symbolic form is spec-identical
across bash/dash/busybox-ash/zsh and degrades to mktemp's 0600
(pre-fix behavior) rather than corrupting perms if chmod rejects it.
- Move the new-file chmod after the content stream so the temp file
stays owner-writable while cat runs.
- Run the chmod on a '[ ! -e "$t" ]' check after cat instead of the
stat/else branch, keeping the overwrite path untouched.
- Update the stale perms comment #70856 called out (new files did NOT
land with default umask perms pre-fix).
- Tests: select the atomic-write script by content instead of call
order (the previous last-call capture only worked because the bare
MagicMock's falsy-exit early return suppressed later execs), assert
behavior at explicit umasks 0022/0002/0077 via parametrize, add an
overwrite mode-preservation regression guard, and dedupe the
real-subprocess env fake into make_real_subprocess_env() shared with
TestSearchFilesFallbackHiddenPaths.
(webtecnica's email mapping already exists in contributors/emails/ on
current main; the PR's check-attribution red was stale-base only.)
# Conflicts:
# tests/tools/test_file_operations.py
98105f31f4