Silent merge strat changes

[jloa]

So, what i've discovered is that the provide merge strategy was silently changed from mergeDataOrFn (in 2.6.x) to mergeData (2.7.x / 3.x).
Which totally breaks the LC of the provide/inject workflow, which broke our app in production when migrating.
I've found the change, i've made the fix for 2.7, but we are stuck on 2.7 now coz 3.x can't be fixed.

BUT! the question remains: Why this change was made silently? Not a single word about this life-breaking change in the changelog

See for yrself https://jsfiddle.net/jloa/cuhwoj3v/

Moreover, we actually can't migrate on 3.x coz @yyx990803 decided to remove the default merge strats for some weird reason.

Why not leave us have our own strats?!

// that simple change
const strat = (strats && strats[key]) || internalOptionMergeStrats[key];

So the strat was swapped silently and we actually can't make it work as it used to (as we want it to).

So.

1. Why these kinda changes are being made silently?
2. Why remove the customization (default strats change api)?
3. How do we migrate to vue3 now without the ability to swap default strats? (ofc we can just throw away the internal provide/inject options and write our own, but that's not an option considering time consumption and the fact that there's a built-in mechanism already or ofc we could just make an npm-patch for vue3 to make it work as we want)