Require = for option argument assignment

[jules43]

I'd like to use the optional argument feature:

@click.group()
@click.option("--csvfile", is_flag=False, flag_value="kasadata.csv", default=None, help="Name of CSV file to write to")
async def cli(csvfile: str)
    click.echo(csvfile)

@cli.command()
asyn def cmd()
   click.echo("cmd")

Is there a way to require an '=' for the option argument?

What I'm after is:

cli cmd
    None
    cmd
cli --csvfile=myfile
   myfile
   cmd
cli --csvfile cmd
    kasadata.csv
    cmd

The last of these doesn't produce the result I want, as the 'cmd' becomes the filename. If I could require an '=' for assignment then I could get the behaviour I'm after.

Thanks