Add clean diff indication for multidoc specs (#54)

Just like this:

```
CephConfig:
~ global cephx_sign_messages true -> false
CephOSDConfig:
~ require_min_compat_client luminous -> reef
```

Depends on #53

Signed-off-by: Igor Shishkin <me@teran.dev>

commands/diff/diff.go

@@ -40,6 +40,10 @@ func Diff(ctx context.Context, ac DiffConfig) error {
 				return err
 			}
 
+			if len(descs) > 1 && len(changes) > 0 {
+				ac.Printer.Printf("%s:\n", desc.Kind)
+			}
+
 			for _, change := range changes {
 				log.WithFields(log.Fields{
 					"component": "command",
@@ -66,6 +70,10 @@ func Diff(ctx context.Context, ac DiffConfig) error {
 				return err
 			}
 
+			if len(descs) > 1 && len(changes) > 0 {
+				ac.Printer.Printf("%s:\n", desc.Kind)
+			}
+
 			for _, change := range changes {
 				log.WithFields(log.Fields{
 					"component": "command",

commands/diff/diff_test.go

@@ -90,3 +90,66 @@ func TestDiffCephOSDConfig(t *testing.T) {
 	})
 	r.NoError(err)
 }
+
+func TestDiffMultidoc(t *testing.T) {
+	r := require.New(t)
+
+	m := service.NewMock()
+	defer m.AssertExpectations(t)
+
+	p := printer.NewMock()
+	defer p.AssertExpectations(t)
+
+	m.On("DiffCephConfig", models.CephConfig{
+		"global": {
+			"test": "value",
+		},
+	}).Return([]models.CephConfigDifference{
+		{
+			Kind:    models.CephConfigDifferenceKindAdd,
+			Section: "mon",
+			Key:     "test_key",
+			Value:   ptr.String("value"),
+		},
+		{
+			Kind:     models.CephConfigDifferenceKindChange,
+			Section:  "osd.3",
+			Key:      "test_key",
+			OldValue: ptr.String("old_value"),
+			Value:    ptr.String("value"),
+		},
+		{
+			Kind:    models.CephConfigDifferenceKindRemove,
+			Section: "osd",
+			Key:     "test_key",
+		},
+	}, nil).Once()
+
+	m.On("DiffCephOSDConfig", models.CephOSDConfig{
+		AllowCrimson:           true,
+		BackfillfullRatio:      0.9,
+		FullRatio:              0.95,
+		NearfullRatio:          0.85,
+		RequireMinCompatClient: "luminous",
+	}).Return([]models.CephOSDConfigDifference{
+		{
+			Key:      "allow_crimson",
+			OldValue: "false",
+			Value:    "true",
+		},
+	}, nil).Once()
+
+	call1 := p.On("Printf", "%s:\n", []any{"CephConfig"}).Return().Once()
+	call2 := p.On("Green", "+ %s %s %s", []any{"mon", "test_key", "value"}).Return().NotBefore(call1).Once()
+	call3 := p.On("Yellow", "~ %s %s %s -> %s", []any{"osd.3", "test_key", "old_value", "value"}).Return().NotBefore(call2).Once()
+	call4 := p.On("Red", "- %s %s", []any{"osd", "test_key"}).Return().NotBefore(call3).Once()
+	call5 := p.On("Printf", "%s:\n", []any{"CephOSDConfig"}).Return().NotBefore(call4).Once()
+	p.On("Yellow", "~ %s %s -> %s", []any{"allow_crimson", "false", "true"}).Return().NotBefore(call5).Once()
+
+	err := Diff(context.Background(), DiffConfig{
+		Printer:  p,
+		Service:  m,
+		SpecFile: "testdata/multidoc.yaml",
+	})
+	r.NoError(err)
+}

commands/diff/testdata/multidoc.yaml

@@ -0,0 +1,13 @@
+---
+kind: CephConfig
+spec:
+  global:
+    test: value
+---
+kind: CephOSDConfig
+spec:
+    allow_crimson: true
+    backfillfull_ratio: 0.9
+    full_ratio: 0.95
+    nearfull_ratio: 0.85
+    require_min_compat_client: luminous

printer/mock.go

@@ -20,6 +20,10 @@ func (m *Mock) HiRed(format string, a ...any) {
 	m.Called(format, a)
 }
 
+func (m *Mock) Printf(format string, a ...any) {
+	m.Called(format, a)
+}
+
 func (m *Mock) Println(a ...any) {
 	m.Called(a)
 }

printer/printer.go

@@ -9,6 +9,7 @@ import (
 type Printer interface {
 	Green(format string, a ...any)
 	HiRed(format string, a ...any)
+	Printf(format string, a ...any)
 	Println(a ...any)
 	Red(format string, a ...any)
 	Yellow(format string, a ...any)
@@ -30,6 +31,10 @@ func (p *printer) HiRed(format string, a ...any) {
 	color.HiRed(format, a...)
 }
 
+func (p *printer) Printf(format string, a ...any) {
+	fmt.Printf(format, a...)
+}
+
 func (p *printer) Println(a ...any) {
 	fmt.Println(a...)
 }