clone command cli pattern is weird

The command is documented as 
```
g3t clone --help
Usage: g3t clone [OPTIONS]

  Clone meta and files from remote.

Options:
  --project_id TEXT             Gen3 program-project G3T_PROJECT_ID
```

The project id is a required argument, so why is it passed as a flag?

Rather then 
```
g3t clone --project_id my-cool-project
```

it should be something like:
```
g3t clone my-cool-project
```