tea upgrade update CLI to latest version

[mittalyashu]

Add tea upgrade command to update to CLI to latest version instead of running this command sh <(curl https://tea.xyz) again and again.

[davdroman]

Agreed, this feels like a missing feature in my book.

[mxcl]

There is also tea -S tea.

I agree it being less explicit is weird.

[davdroman]

Whoa, I had no idea. Meta af. Thanks for the tip 👍