Now that clap#2624 has been resolved, we can and should test both variants.

See also 9995c63.

There is a race condition between the writing thread and the command.
It is easily possible that on the developer's machine, the writing
thread is always faster, filling the kernel's buffer of the stdin pipe,
thus succeeding the write. It is also easily possible that on the busy
CI machines, the child command runs first for whatever reason, and exits
early, thus killing the pipe, which causes the later write to fail. This
results in a flaky test. Let's prevent flaky tests.

chore(deps): update rust crate rayon to 1.9

tests: Harden two tests, prevent 4 flaky tests (cat, numfmt, sort, split, tee)

…ile_busy_error

Android CI: workaround: run builds with retry

cargo: fix feature = "cargo-clippy" deprecation

…hars

printf: Make printf operate on bytes instead of strings

…ed with '%0c' or '%0s'

printf: '%0c' and '%0s' should fail

…teractive_update

cp: fix flaky test test_cp_arg_interactive_update, document adjacent bug

…l_utility

test utilities: easy way to simulate terminal context

ci: use codecov token in CICD/GnuTests workflows

chore(deps): update rust crate walkdir to 2.5

tests/common/util.rs: add `cfg(feature = "env")`

…thing

cat: Handle all flags correctly

Bump mio from 0.8.10 to 0.8.11

…time

One of the GNU tests checks for the exact error message.

…message

This is explicitly tested in the GNU tests.

This function is by necessity ill-defined: Depending on the context,
'..' is either the logical parent directory, sometimes the physical
parent directory. This function can only work for the latter case,
in which case `Path::canonicalize` is often a better approach.

…gh-release-2.x

chore(deps): update softprops/action-gh-release action to v2

…bin_limited_fds

Fix/flaky `split` round robin limited fds

…root

chown+chgrp+chmod: Fix handling of preserve root flag and error messages