```console
$ teller show
[source (dotenv)]: DEV_DB = ma***
[source (dotenv)]: EMPTY = tr***
[target (dotenv)]: TARGET_ONLY = tr***
$ teller copy --from source/dev --to target/prod
$ teller show
[source (dotenv)]: DEV_DB = ma***
[source (dotenv)]: EMPTY = tr***
[target (dotenv)]: DEV_DB = ma***
[target (dotenv)]: EMPTY = tr***
[target (dotenv)]: TARGET_ONLY = tr***
$ teller copy --from source/dev --to target/prod --replace
$ teller show
[source (dotenv)]: DEV_DB = ma***
[source (dotenv)]: EMPTY = tr***
[target (dotenv)]: DEV_DB = ma***
[target (dotenv)]: EMPTY = tr***
```