Do a large chunk of the move to go

This commit moves a huge chunk of the code to go. The TODO.md document
indicates what is left to be done.

cmd/blind_update.go

@@ -0,0 +1,54 @@
+package cmd
+
+import (
+	wisski_distillery "github.com/FAU-CDI/wisski-distillery"
+	"github.com/FAU-CDI/wisski-distillery/env"
+	"github.com/tkw1536/goprogram/exit"
+)
+
+// BlindUpdate is the 'blind-update' command
+var BlindUpdate wisski_distillery.Command = blindUpdate{}
+
+type blindUpdate struct {
+	Force       bool `short:"f" long:"force" description:"force running blind-update even if AutoBlindUpdate is set to false"`
+	Positionals struct {
+		Slug []string `positional-arg-name:"SLUG" required:"0" description:"slug of instance(s) to run blind-update in"`
+	} `positional-args:"true"`
+}
+
+func (blindUpdate) Description() wisski_distillery.Description {
+	return wisski_distillery.Description{
+		Requirements: env.Requirements{
+			NeedsConfig: true,
+		},
+		Command:     "blind_update",
+		Description: "Runs the blind update in the provided instances",
+	}
+}
+
+var errBlindUpdateFailed = exit.Error{
+	Message:  "Failed to run blind update script for instance %q: exited with code %s",
+	ExitCode: exit.ExitGeneric,
+}
+
+func (bu blindUpdate) Run(context wisski_distillery.Context) error {
+	instances, err := context.Environment.Instances(bu.Positionals.Slug...)
+	if err != nil {
+		return err
+	}
+
+	for _, instance := range instances {
+		if !(instance.IsBlindUpdateEnabled() || bu.Force) {
+			context.EPrintf("skipping instance %q\n", instance.Slug)
+			continue
+		}
+		context.EPrintf("Updating instance %s\n", instance.Slug)
+
+		code := instance.Shell(context.IOStream, "/utils/blind_update.sh")
+		if code != 0 {
+			return errBlindUpdateFailed.WithMessageF(instance.Slug, code)
+		}
+	}
+
+	return nil
+}