Make "OverwriteWithEmptyValue" in config struct to be set by any meth…

…od. (darccio#133)

Make "OverwriteWithEmptyValue" in config struct to be set by any method.

this make the merge more customizable. In cases, where request toggles a boolean value and the the request message can change a "true" value to false we can pass the flag to merge accordingly, which is not possible otherwise.

merge.go

@@ -46,7 +46,6 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, co
 	typeCheck := config.TypeCheck
 	overwriteWithEmptySrc := config.overwriteWithEmptyValue
 	overwriteSliceWithEmptySrc := config.overwriteSliceWithEmptyValue
-	config.overwriteWithEmptyValue = false
 
 	if !src.IsValid() {
 		return
@@ -246,6 +245,11 @@ func WithOverride(config *Config) {
 	config.Overwrite = true
 }
 
+// WithOverwriteWithEmptyValue will make merge override non empty dst attributes with empty src attributes values.
+func WithOverwriteWithEmptyValue(config *Config) {
+	config.overwriteWithEmptyValue = true
+}
+
 // WithOverride will make merge override empty dst slice with empty src slice.
 func WithOverrideEmptySlice(config *Config) {
 	config.overwriteSliceWithEmptyValue = true