Use indentation of 2 when rewriting auto-migrated config file (#4312)

- **PR Description**

Use indentation of 2 when rewriting auto-migrated config file. This
seems to be what most people use when indenting yaml files, and it seems
to make more sense than the default of 4. We also use it the example
config in Config.md.

pkg/utils/yaml_utils/yaml_utils.go

@@ -1,6 +1,7 @@
 package yaml_utils
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 
@@ -34,7 +35,7 @@ func UpdateYamlValue(yamlBytes []byte, path []string, value string) ([]byte, err
 	}
 
 	// Convert the updated YAML node back to YAML bytes.
-	updatedYAMLBytes, err := yaml.Marshal(body)
+	updatedYAMLBytes, err := yamlMarshal(body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert YAML node to bytes: %w", err)
 	}
@@ -126,7 +127,7 @@ func TransformNode(yamlBytes []byte, path []string, transform func(node *yaml.No
 	}
 
 	// Convert the updated YAML node back to YAML bytes.
-	updatedYAMLBytes, err := yaml.Marshal(body)
+	updatedYAMLBytes, err := yamlMarshal(body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert YAML node to bytes: %w", err)
 	}
@@ -170,7 +171,7 @@ func RenameYamlKey(yamlBytes []byte, path []string, newKey string) ([]byte, erro
 	}
 
 	// Convert the updated YAML node back to YAML bytes.
-	updatedYAMLBytes, err := yaml.Marshal(body)
+	updatedYAMLBytes, err := yamlMarshal(body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert YAML node to bytes: %w", err)
 	}
@@ -227,7 +228,7 @@ func Walk(yamlBytes []byte, callback func(node *yaml.Node, path string) bool) ([
 	}
 
 	// Convert the updated YAML node back to YAML bytes.
-	updatedYAMLBytes, err := yaml.Marshal(body)
+	updatedYAMLBytes, err := yamlMarshal(body)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert YAML node to bytes: %w", err)
 	}
@@ -273,3 +274,12 @@ func walk(node *yaml.Node, path string, callback func(*yaml.Node, string) bool)
 
 	return didChange, nil
 }
+
+func yamlMarshal(node *yaml.Node) ([]byte, error) {
+	var buffer bytes.Buffer
+	encoder := yaml.NewEncoder(&buffer)
+	encoder.SetIndent(2)
+
+	err := encoder.Encode(node)
+	return buffer.Bytes(), err
+}

pkg/utils/yaml_utils/yaml_utils_test.go

@@ -54,7 +54,6 @@ func TestUpdateYamlValue(t *testing.T) {
 			in:          "foo:\n  bar: baz\n",
 			path:        []string{"foo", "bar"},
 			value:       "qux",
-			// indentation is not preserved. See https://github.com/go-yaml/yaml/issues/899
 			expectedOut: "foo:\n  bar: qux\n",
 			expectedErr: "",
 		},
@@ -138,7 +137,6 @@ func TestRenameYamlKey(t *testing.T) {
 			in:          "foo:\n  bar: 5\n",
 			path:        []string{"foo", "bar"},
 			newKey:      "baz",
-			// indentation is not preserved. See https://github.com/go-yaml/yaml/issues/899
 			expectedOut: "foo:\n  baz: 5\n",
 			expectedErr: "",
 		},
@@ -147,7 +145,6 @@ func TestRenameYamlKey(t *testing.T) {
 			in:          "foo:\n  bar: 5\n",
 			path:        []string{"foo"},
 			newKey:      "qux",
-			// indentation is not preserved. See https://github.com/go-yaml/yaml/issues/899
 			expectedOut: "qux:\n  bar: 5\n",
 			expectedErr: "",
 		},
@@ -288,7 +285,6 @@ func TestWalk_inPlaceChanges(t *testing.T) {
 				}
 				return false
 			},
-			// indentation is not preserved. See https://github.com/go-yaml/yaml/issues/899
 			expectedOut: "x:\n  y: 7\n",
 		},
 		{
@@ -301,7 +297,6 @@ func TestWalk_inPlaceChanges(t *testing.T) {
 				}
 				return false
 			},
-			// indentation is not preserved. See https://github.com/go-yaml/yaml/issues/899
 			expectedOut: "x:\n  - y: 7\n",
 		},
 	}
@@ -367,7 +362,7 @@ foo:
 			transform: transformIntValueToString,
 			expectedOut: `foo:
   bar: "2"
-`, // Note the indentiation change and newlines because of how it re-marshalls
+`, // Note the trailing newline changes because of how it re-marshalls
 		},
 		{
 			name: "Does nothing when already transformed",