WIP rewrite the daemon

cmd subdir does not build on purpose, it's only left in tree to grab old
code and move it to github.com/zrepl/zrepl/daemon

cmd/daemon.deact/job/job.go

@@ -0,0 +1,47 @@
+package job
+
+import (
+	"context"
+	"github.com/zrepl/zrepl/logger"
+)
+
+type Logger = logger.Logger
+
+type contextKey int
+
+const (
+	contextKeyLog contextKey = iota
+	contextKeyWakeup
+)
+
+func GetLogger(ctx context.Context) Logger {
+	if l, ok := ctx.Value(contextKeyLog).(Logger); ok {
+		return l
+	}
+	return logger.NewNullLogger()
+}
+
+func WithLogger(ctx context.Context, l Logger) context.Context {
+	return context.WithValue(ctx, contextKeyLog, l)
+}
+
+func WithWakeup(ctx context.Context) (context.Context, WakeupChan) {
+	wc := make(chan struct{}, 1)
+	return context.WithValue(ctx, contextKeyWakeup, wc), wc
+}
+
+type Job interface {
+	Name() string
+	Run(ctx context.Context)
+	Status() interface{}
+}
+
+type WakeupChan <-chan struct{}
+
+func WaitWakeup(ctx context.Context) WakeupChan {
+	wc, ok := ctx.Value(contextKeyWakeup).(WakeupChan)
+	if !ok {
+		wc = make(chan struct{})
+	}
+	return wc
+}