config/env.go
func (c *EnvConfig) Merge(o *EnvConfig) *EnvConfig {
	if c == nil {
		if o == nil {
			return nil
		}
		return o.Copy()
	}

	if o == nil {
		return c.Copy()
	}

	r := c.Copy()

	if o.Blacklist != nil {
		r.Blacklist = append(r.Blacklist, o.Blacklist...)
	}

	if o.Custom != nil {
		r.Custom = append(r.Custom, o.Custom...)
	}

	if o.Pristine != nil {
		r.Pristine = o.Pristine
	}

	if o.Whitelist != nil {
		r.Whitelist = append(r.Whitelist, o.Whitelist...)
	}

	return r
}
func (c *EnvConfig) Merge(o *EnvConfig) *EnvConfig {
	if c == nil {
		if o == nil {
			return nil
		}
		return o.Copy()
	}

	if o == nil {
		return c.Copy()
	}

	r := c.Copy()

	if o.Blacklist != nil {
		r.Blacklist = append(r.Blacklist, o.Blacklist...)
	}

	if o.Custom != nil {
		r.Custom = append(r.Custom, o.Custom...)
	}

	if o.Pristine != nil {
		r.Pristine = o.Pristine
	}

	if o.Whitelist != nil {
		r.Whitelist = append(r.Whitelist, o.Whitelist...)
	}

	return r
}
// Merge combines all values in this configuration with the values in the other
// configuration, with values in the other configuration taking precedence.
// Maps and slices are merged, most other values are overwritten. Complex
// structs define their own merge functionality.