build(make): require cargo-nextest for make test with explicit escape hatch (backlog#1153 infra-14)
cargo-nextest changes test semantics — it runs each test in its own process
(so serial_test's #[serial] mutex does not serialize across tests) and is the
only runner that honours .config/nextest.toml [test-groups] (e.g. the
ecstore-serial-flaky serialization guard). CI installs and runs nextest, but
`make test` only warned when it was missing and then silently fell back to
`cargo test`, which runs with different serialization behaviour than CI and can
mask or invent flakes.
Make cargo-nextest a hard dependency of `make test`:
- Missing nextest now fails `make test` with a clear message and install
instructions (`cargo install cargo-nextest --locked` or a prebuilt binary
via https://nexte.st/docs/installation/).
- Set RUSTFS_ALLOW_CARGO_TEST_FALLBACK=1 to opt into the plain `cargo test`
fallback anyway; it prints a loud warning that serialization semantics differ
from CI and .config/nextest.toml test-groups will NOT apply.
- The check stays cheap (command -v). The warn-only test-deps prerequisite is
dropped from check.mak in favour of recipe-level gating.
Install docs live in the make-layer error message plus a header comment in
tests.mak, with a single-line note in CONTRIBUTING.md (kept minimal to avoid
conflicting with #4667 / infra-9, which rewrites the verification sections).
No CI change: .github/workflows/ci.yml already runs cargo nextest and
.github/actions/setup/action.yml already installs it.
Refs rustfs/backlog#1153 (infra-14), master plan #1155.
Signed-off-by: Zhengchao An <anzhengchao@gmail.com>
Zhengchao An