Extend re-add command to add new files

[eugenesvk]

Is your feature request related to a problem? Please describe.

Following #3142 I've switched from add to re-add to not break encrypted files

However, re-add can't add new files, so you get not managed error and have to remember again that there is a difference between add and re-add

Describe the solution you'd like

I'd like to have just one command that can handle both cases, so some kind of option/flag that asks re-add to also be able to add new files would be great!

Describe alternatives you've considered

Not sure, thought about maybe checking the error message in an aliased launcher and relaunch the same command with add instead
Or maybe checking if a file is managed beforehand

But that seems too brittle

Additional context

N/a

[twpayne]

Just a quick note on this. This makes most sense with exact_ directories, where chezmoi manages all files in a directory, including the deletion of unmanaged files.

[twpayne]

This is actually a dup of #2298.

[eugenesvk]

Doesn't seem like a dupe, I don't want to add the whole directory, only a specific file. In my case there is no chezmoi add ~/zack_setup_env initial adding step