test(alias): cover empty RC_HOST alias name

[overtrue]

Related issue(s)

None.

Background

Recent alias error handling work changed malformed RC_HOST_* environment aliases to report structured usage errors from the alias list command. Existing subprocess coverage checks invalid schemes and malformed credential percent encoding, but the empty alias-name variable RC_HOST_ was only covered indirectly by the core parser behavior.

Root cause

RC_HOST_ reaches AliasManager::list() through the environment alias loader and fails before any alias is built. Before the recent alias command error-code handling, this path could fall back to a generic alias-list error response instead of preserving the core Config usage-error exit code and JSON metadata.

Solution

Add a focused crates/cli/tests/env_alias.rs subprocess regression for rc alias list --json with RC_HOST_ set. The test verifies exit code 2, stderr JSON, usage_error metadata, and that credential material from the malformed environment value is not echoed.

Validation

• cargo test -p rustfs-cli --test env_alias alias_list_rejects_empty_rc_host_alias_name_as_usage_error
• cargo test -p rustfs-cli --test env_alias
• make pre-commit

[Copilot]

Pull request overview

Adds a focused CLI integration regression test for malformed environment alias handling when RC_HOST_ has no alias name.

Changes:

• Adds a subprocess test for rc alias list --json with RC_HOST_.
• Verifies usage-error exit code, JSON error metadata, and credential redaction from stderr.

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