Setup a default behavior when no subcommand used

[fu050409]

Describe the feature

Hi! Sometimes, if our CLI tool get no args, it should work the same as one of it's subCommands, like farm and vite, Vite and Farm both open a development server if no args is given. This works the same as farm dev and vite dev.

Now citty will throw an error if there is no args and run function is not defined for main. But if run function for main is defined, and you're using a subcommand, citty will call the run function defined in main repeatly after called run function defined in subCommand. This confused me, I think it shouldn't call the main handler function when using a subcommand.

Therefore, can we provide a api to setup a default bahavior with no subcommand used?

Such as:

subCommands: {
    dev,
},
default: 'dev'

If so, I'd like to work with this issue :)

Additional information

• Would you be willing to help implement this feature?

[zuixinwang]

I think a default subcommand is unnecessary because, without it, the main command would run 👀
Perhaps it's a good idea not to run the run function of the main command when running the sub-command, but compatibility needs to be considered