Yeah that's pretty much the case with Modern Compiler Implementation in {ML, Java, C} by Appel. The Java and C ones are basically transliterated ML and not everyone appreciates that.
On the one hand, people do buy the Java and C books. On the other hand, I think they eventually realize it's probably easier to learn an ML dialect and learn the "real" code.
This may or may not apply to the git book though, since doing it in Ruby is already not "idiomatic".
I used to think so too, but tbh I think this will result in either a lot more work than you would like, or your audience are going to end up with one language that is being used ideomatically and the rest of the languages are not being used ideomatically.