add acorn run --update/-u flag to update app if exists

[iwilltry42]

• triggers acorn update logic if app exists
• does not work with --dev/-i
• requires --name/-n to be specified

Ref #466

Notes

• This is not 100% like kubectl apply, as that one does a 3-way patch merge, where it takes into account the last-applied-configuration annotation. This PR does not consider such annotations.

[cjellick]

At first blush, this looks good to me. I'm going to get @ibuildthecloud's input on it

[ibuildthecloud]

I really want this, but the approach should be different. "Run -u" and "update" should be slightly different from each other. Basically "acorn run -u" should be like k8s update and "acorn update" should be like k8s patch.

update today will only change the fields you specify and not touch the other fields. Run -u should ensure all fields exactly match the arguments. So that means run -u will reset fields back to default values if the user didn't specify the flag.

[cjellick]

@iwilltry42 lets definitely try to get this one into v0.4.0. let me know when youve addressed @ibuildthecloud feedback. ill move the issue back to in progress

[iwilltry42]

@ibuildthecloud does this come close to what you'd expect?

[cjellick]

@ibuildthecloud mentioned the approach looks right but he wants a new command a different verb that is the equivalent of update --patch=false. We decided acorn replace should be that verb.

Can you add this @iwilltry42 ?

Moving this out to v0.4.1, which will basically be a milestone for this and one or two other issues that aren't quite ready.

edit: was just flag that needed chagned