do not require --process-group on every case of fly scale count

[dangra]

Change Summary

What and Why: fly scale count requires --process-group when 'app' process group isn't present but it shouldn't in every case.

How: Deal with multi process group syntax and group name passed by group name

Related to: #2557

I am testing this on a GPU app that have 3 different process group and none is named "app". That is why the groups resembles GPU kinds so closely.

~
❯ fly scale count 4
Error: Attempting to scale unknown process groups [app] but valid names are [40gb 80gb l40s].
 Use `fly scale count COUNT --process-group=NAME`
 or multi group syntax `fly scale count NAME1=COUNT1 NAME2=COUNT2 ...`

~ took 2s
❯ fly scale count foo=4
Error: Attempting to scale unknown process groups [foo] but valid names are [40gb 80gb l40s].
 Use `fly scale count COUNT --process-group=NAME`
 or multi group syntax `fly scale count NAME1=COUNT1 NAME2=COUNT2 ...`

~
❯ fly scale count foo=4 bar=3
Error: Attempting to scale unknown process groups [foo bar] but valid names are [40gb 80gb l40s].
 Use `fly scale count COUNT --process-group=NAME`
 or multi group syntax `fly scale count NAME1=COUNT1 NAME2=COUNT2 ...`

~
❯ fly scale count foo=4 bar=3 l40s=5
Error: Attempting to scale unknown process groups [foo bar] but valid names are [40gb 80gb l40s].
 Use `fly scale count COUNT --process-group=NAME`
 or multi group syntax `fly scale count NAME1=COUNT1 NAME2=COUNT2 ...`

---

Documentation

• Fresh Produce
• In superfly/docs, or asked for help from docs team
• n/a

[andie787]

I like this helpful output!

The multi group syntax is in docs, but not in flyctl output or --help anywhere (I'll look at that next).