I got a scenario here, that I would like to discuss and hopefully create a source for docs, for what a developer should really think about to prevent causing hash changes.
I'm making something, that might seem like a very small change in my code, which has quite large effect on long-term caching.

I'm writing this issue in docs, because I'm sure it's expected, just that I want to be able to understand why this is happening, and hopefully help others as well.

Example repo is here (using webpack@2.2.0-rc.7 and webpack-chunk-hash@0.3.0):
https://github.com/jouni-kantola/webpack-output-by-build-type/tree/why-hash-change

Here goes the scenario:

1. I build:

2. I change module-a.js from:

import is from 'is-thirteen';

export const a = () => console.log('module a says 12 + 1 === 13', is(12 + 1).thirteen());

to:

export const a = () => console.log('hello world');

3. I build yet again:

So to what I think needs to be documented:

1. What types of changes should a developer really be aware of when making changes.
2. In this build, is-thirteen changed ID from 59 to 85, and that caused three bundles to be cache busted. In a larger app that could be quite a lot of code that needs to be shipped again to the end-user. Is there anyway to prevent this small change, from having this large effect?
3. Is there anyway of preventing the vendor bundle from changing hash, when changing consuming code?

I think I've done the most important bit, to extract the manifest, but still it's very easy to get chunks cache busted. There are loads of blogs discussing this, but I still believe the truly nitty gritty is missing to be documented.