What is the upgrade path to go from 13.2.6 to 15.0.0?
From here: Upgrading GitLab | GitLab
since your version falls between 13.1.11 and 13.8.8, your first upgrade is to 13.8.8, then 13.12.15, then 14.0.12 and so on.
However, I do suggest, due to the amount of problems with 14.x upgrades, that once you get to 14.0.12, that you then upgrade through each point release, so 14.1.0, 14.2.0, 14.3.0 and so on all the way up to 14.10.0. Then upgrade to latest 14.10.x release and go to 15.x after this.
As per the link I provided to the upgrade docs, read this, and ensure that before doing the next upgrade, you wait for background migrations to finish. Only then can you start to upgrade to the next release on the upgrade path. If you attempt to upgrade before it is finished, you will break your install. The docs explain how to check background migration status.
Would the same apply to this upgrade path?
14.5.2 → 14.9.4 → 14.10.3 → 15.0.0
Should I install the point patches: 14.6.0, 14.7.0, 14.8.0 before going to 14.9.4?
Then 14.10.0 before going to 14.10.3?
According to the upgrade path it’s not necessary, but from experience and all the problems people have encountered I would do it like how I mentioned. There are others here who have also suggested the same as me.
Generally I upgrade every time a release is made, which in some cases can be every week or every two weeks for some point releases. By doing it regularly, it seems there is far less chance of problems being encountered.
I would probably go with the latest version in each minor series, to have fewer known security problems while doing it, but apart from that I agree with @iwalker, i.e. go through:
13.8.8 → 13.12.15 → 14.0.12 → 14.1.8 → 14.2.7 → 14.3.6 → 14.4.5 → 14.5.4 → 14.6.7 → 14.7.7 → 14.8.6 → 14.9.5 → 14.10.4 → 15.0.1
To @ergononsum: You can jump in at either 14.9.5 (the officially recommended path) or at 14.5.4 or 14.6.7 to follow my suggestion. It doesn’t make that much sense to take 14.5.4 first when you’re upgrading further anyway, but I guess it does reduce the chance of problem a little bit, but it’s probably from “very low” to “very very low”.
As @iwalker I generally upgrade often, but last year some factors caused us to fall a bit behind, then I chose as described - but some of the mentioned releases have come out after the next minor, e.g. I don’t think we’ve ever run 14.9.5 because we were already on 14.10 when that came out (which probably also explains why the path @ergononsum has found mentions 14.9.4).