bs refuses to start when any unknown BS_* environment variable is set, without naming it #1061

Observed

bs parses every environment variable with the BS_ prefix as a setting. An unknown one makes it exit before doing anything, and the error does not name the variable:

$ BS_FOO=1 bs --version
Error: unrecognised option

$ BS_CLI=x bs --settings
Error: unrecognised option

This applies to every invocation (node start, --settings, --version, store commands). A variable meant for an unrelated tool (here a test script's BS_CLI) is enough to prevent startup, and nothing in the output points to the environment as the cause.

Expected

At minimum, the error names the offending variable and its source, e.g. Error: unrecognised option 'cli' (environment variable BS_CLI). Optionally, unknown BS_* variables are ignored with a warning instead of being fatal.

Environment

bs 4.0.3240 (server 0911d79c), also seen on 4.0.3228; Linux, static release build.