Capacity to manage NoWrites at LocalConfig level

[SR-G]

Except if i missed it, i don't see how to handle at "LocalConfig" level the Write/Persist behavior.

	localCfg, err := gitconfig.LoadConfig(".git/config")
	if err != nil {
		log.Fatal(err)
	}
        localCfg.Write() <-- not available
        localCfg.NoWrites = false <-- not possible

The "NoWrites" behavior is probably inherited from "global config", but for usages only relying on LocalConfig (for example), it should be possible to locally overwrite it.

[dominikschulz]

I think this is a valid request.