`firebase emulators:export` doesn't support / warn about `--only`

[ggirotto]

[REQUIRED] Environment info

firebase-tools: 10.1.2

Platform: macOS 12.1

[REQUIRED] Steps to reproduce

1. Start emulators suite
2. Run firebase emulators:export --only firestore

[REQUIRED] Expected behavior

Only firestore metadata should be exported.

[REQUIRED] Actual behavior

Other metadata - auth as an example - is exported as well. The --only flag seems to be ignored/not used

Logs when running with --debug

[2022-01-21T17:48:32.520Z] >>> HTTP REQUEST GET http://localhost:4400/

[2022-01-21T17:48:32.550Z] <<< HTTP RESPONSE 200 {"x-powered-by":"Express","vary":"Origin","content-type":"application/json; charset=utf-8","content-length":"51","etag":"W/"33-cqbzNA/eKm0XcA5dWyWSdlXsGtQ"","date":"Fri, 21 Jan 2022 17:48:32 GMT","connection":"keep-alive","keep-alive":"timeout=5"} i Found running emulator hub for project <PROJECT_ID> at http://localhost:4400 ? The directory /Users/<PATH>/a already contains export data. Exporting again to the same directory will overwrite all data. Do you want to continue? Yes i Exporting data to: /Users/<PATH>/a [2022-01-21T17:48:35.915Z] >>> HTTP REQUEST POST http://localhost:4400/_admin/export
{"path":"/Users/<PATH>/a"} [2022-01-21T17:48:35.950Z] <<< HTTP RESPONSE 200 {"x-powered-by":"Express","vary":"Origin","content-type":"application/json; charset=utf-8","content-length":"16","etag":"W/"10-MxB4y4MLcx6QDsp8b8vgp7iFMFo"","date":"Fri, 21 Jan 2022 17:48:35 GMT","connection":"keep-alive","keep-alive":"timeout=5"}

[google-oss-bot]

This issue does not seem to follow the issue template. Make sure you provide all the required information.