Merging multi-pitch routes, info lost

[rouletout]

What happened?

When merging 2 routes, one of them with individual grades per pitch (e.g. 6a, 7a, 6c) and one with just one grade the pitch grade info is lost.

Ideally also provide screenshots:

What you expected:

That the route with more info (in that case individual grades and / or length) prevails.

[Mdemaillard]

see #3620

[rouletout]

@Mdemaillard I'm not sure this is the same - one is structured tags (that are lost), the other is pitch info (grades and legth per pitch). i just merged this one https://sandpit.thecrag.com/climbing/mexico/el-potrero-chico/route/11935411 and it seems ok - i'll do more testing

[rouletout]

I also tested with 2 routes with grades for each pitch, the pitch info is not lost but it does not merge the grades per pitch, just updates the general grade to the max grade. See screenshots:

The two routes being merged before the merge:

The merged route:

The grade contributions of the merged route:

The issue is that the detailed pitch grade contributions of the disappearing route are lost.