Refactor config commit stuff to support restartless updates better

Includes restartless updates of the GUI settings (listening port etc) as
a proof of concept.

internal/model/model.go

@@ -17,6 +17,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strings"
 	stdsync "sync"
@@ -1718,6 +1719,37 @@ func (m *Model) String() string {
 	return fmt.Sprintf("model@%p", m)
 }
 
+func (m *Model) VerifyConfiguration(from, to config.Configuration) error {
+	return nil
+}
+
+func (m *Model) CommitConfiguration(from, to config.Configuration) bool {
+	// TODO: This should not use reflect, and should take more care to try to handle stuff without restart.
+
+	// Adding, removing or changing folders requires restart
+	if !reflect.DeepEqual(from.Folders, to.Folders) {
+		return false
+	}
+
+	// Removing a device requres restart
+	toDevs := make(map[protocol.DeviceID]bool, len(from.Devices))
+	for _, dev := range to.Devices {
+		toDevs[dev.DeviceID] = true
+	}
+	for _, dev := range from.Devices {
+		if _, ok := toDevs[dev.DeviceID]; !ok {
+			return false
+		}
+	}
+
+	// All of the generic options require restart
+	if !reflect.DeepEqual(from.Options, to.Options) {
+		return false
+	}
+
+	return true
+}
+
 func symlinkInvalid(isLink bool) bool {
 	if !symlinks.Supported && isLink {
 		SymlinkWarning.Do(func() {

internal/model/model_test.go

@@ -317,21 +317,22 @@ func TestDeviceRename(t *testing.T) {
 
 	defer os.Remove("tmpconfig.xml")
 
-	cfg := config.New(device1)
-	cfg.Devices = []config.DeviceConfiguration{
+	rawCfg := config.New(device1)
+	rawCfg.Devices = []config.DeviceConfiguration{
 		{
 			DeviceID: device1,
 		},
 	}
+	cfg := config.Wrap("tmpconfig.xml", rawCfg)
 
 	db, _ := leveldb.Open(storage.NewMemStorage(), nil)
-	m := NewModel(config.Wrap("tmpconfig.xml", cfg), protocol.LocalDeviceID, "device", "syncthing", "dev", db)
-	if cfg.Devices[0].Name != "" {
+	m := NewModel(cfg, protocol.LocalDeviceID, "device", "syncthing", "dev", db)
+	if cfg.Devices()[device1].Name != "" {
 		t.Errorf("Device already has a name")
 	}
 
 	m.ClusterConfig(device1, ccm)
-	if cfg.Devices[0].Name != "" {
+	if cfg.Devices()[device1].Name != "" {
 		t.Errorf("Device already has a name")
 	}
 
@@ -342,13 +343,13 @@ func TestDeviceRename(t *testing.T) {
 		},
 	}
 	m.ClusterConfig(device1, ccm)
-	if cfg.Devices[0].Name != "tester" {
+	if cfg.Devices()[device1].Name != "tester" {
 		t.Errorf("Device did not get a name")
 	}
 
 	ccm.Options[0].Value = "tester2"
 	m.ClusterConfig(device1, ccm)
-	if cfg.Devices[0].Name != "tester" {
+	if cfg.Devices()[device1].Name != "tester" {
 		t.Errorf("Device name got overwritten")
 	}
 

internal/model/progressemitter.go

@@ -7,6 +7,7 @@
 package model
 
 import (
+	"fmt"
 	"path/filepath"
 	"reflect"
 	"time"
@@ -37,8 +38,10 @@ func NewProgressEmitter(cfg *config.Wrapper) *ProgressEmitter {
 		timer:    time.NewTimer(time.Millisecond),
 		mut:      sync.NewMutex(),
 	}
-	t.Changed(cfg.Raw())
+
+	t.CommitConfiguration(config.Configuration{}, cfg.Raw())
 	cfg.Subscribe(t)
+
 	return t
 }
 
@@ -81,17 +84,22 @@ func (t *ProgressEmitter) Serve() {
 	}
 }
 
-// Changed implements the config.Handler Interface to handle configuration
-// changes
-func (t *ProgressEmitter) Changed(cfg config.Configuration) error {
+// VerifyConfiguration implements the config.Committer interface
+func (t *ProgressEmitter) VerifyConfiguration(from, to config.Configuration) error {
+	return nil
+}
+
+// CommitConfiguration implements the config.Committer interface
+func (t *ProgressEmitter) CommitConfiguration(from, to config.Configuration) bool {
 	t.mut.Lock()
 	defer t.mut.Unlock()
 
-	t.interval = time.Duration(cfg.Options.ProgressUpdateIntervalS) * time.Second
+	t.interval = time.Duration(to.Options.ProgressUpdateIntervalS) * time.Second
 	if debug {
 		l.Debugln("progress emitter: updated interval", t.interval)
 	}
-	return nil
+
+	return true
 }
 
 // Stop stops the emitter.
@@ -138,3 +146,7 @@ func (t *ProgressEmitter) BytesCompleted(folder string) (bytes int64) {
 	}
 	return
 }
+
+func (t *ProgressEmitter) String() string {
+	return fmt.Sprintf("ProgressEmitter@%p", t)
+}