Split off cli into separate binaries (#37)

* 🎨 Split off cli into separate binaries

This commit splits off the cli into 3 binaries:
- agent
- cli
- provider

The provider now is a separate component that can be tested by itself
and have its own lifecycle. This paves the way to a ligher c3os variant,
HA support and other features that can be provided on runtime.

This is working, but still there are low hanging fruit to care about.

Fixes #14

* 🤖 Add provider bin to releases

* ⚙️ Handle signals

* ⚙️ Reduce buildsize footprint

* 🎨 Scan for providers also in /system/providers

* 🤖 Run goreleaser

* 🎨 Refactoring

cmd/agent/agent.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"syscall"
+
+	"github.com/c3os-io/c3os/internal/bus"
+	"github.com/c3os-io/c3os/internal/utils"
+	events "github.com/c3os-io/c3os/pkg/bus"
+	config "github.com/c3os-io/c3os/pkg/config"
+	"github.com/nxadm/tail"
+)
+
+// setup needs edgevpn and k3s installed locally
+// (both k3s and k3s-agent systemd services)
+func agent(apiAddress string, dir []string, force bool) error {
+
+	os.MkdirAll("/usr/local/.c3os", 0600)
+
+	// Reads config
+	c, err := config.Scan(dir...)
+	if err != nil {
+		return err
+	}
+
+	f, err := ioutil.TempFile(os.TempDir(), "c3os")
+	if err != nil {
+		return err
+	}
+
+	err = ioutil.WriteFile(f.Name(), []byte{}, os.ModePerm)
+	if err != nil {
+		return err
+	}
+
+	t, err := tail.TailFile(f.Name(), tail.Config{Follow: true})
+	if err != nil {
+		return err
+	}
+
+	defer os.RemoveAll(f.Name())
+
+	utils.OnSignal(func() {
+		os.RemoveAll(f.Name())
+	}, syscall.SIGINT, syscall.SIGTERM)
+
+	go func() {
+		for line := range t.Lines {
+			fmt.Println(line.Text)
+		}
+	}()
+
+	_, err = bus.Manager.Publish(events.EventBootstrap, events.BootstrapPayload{APIAddress: apiAddress, Config: c.String(), Logfile: f.Name()})
+	return err
+}