Initialize Steps with a NewSTEPNAME function [#67]

This seems to be be a more natural separation of concerns--the knowledge
of which config fields map to which parts of a Step belong to the Step,
not to the Plan.

internal/run/uninstall.go

@@ -2,6 +2,7 @@ package run
 
 import (
 	"fmt"
+	"github.com/pelotech/drone-helm3/internal/env"
 )
 
 // Uninstall is an execution step that calls `helm uninstall` when executed.
@@ -12,6 +13,15 @@ type Uninstall struct {
 	cmd         cmd
 }
 
+// NewUninstall creates an Uninstall using fields from the given Config. No validation is performed at this time.
+func NewUninstall(cfg env.Config) *Uninstall {
+	return &Uninstall{
+		Release:     cfg.Release,
+		DryRun:      cfg.DryRun,
+		KeepHistory: cfg.KeepHistory,
+	}
+}
+
 // Execute executes the `helm uninstall` command.
 func (u *Uninstall) Execute(_ Config) error {
 	return u.cmd.Run()