The addition of `--set k1=v1,k2=v2` and `--values file1 --values file2` was originally planned in #361.
But it turned out we already had `--values` for existing helmfile commands like `sync`. Duplicated flags doesn't work, obviously.
So this actually add `--state-values-set k1=v1,k2=v2` and `--set-values-file file1 --set-values-file file2`.
They are called "state" values according to the discussion we had at #640Resolves#361
* feat: helmfile as a go library
This removes almost all the dependencies from the helmfile core logic to urfave/cli. `main.go` is now a thin wrapper around the core logic implemented in `pkg/app`.
KUOKA Yusuke