iCloud drive and git repository
I have had bad experiences with this, although specifically in the case of multiple macs syncing the same cloned repo.

I have a couple of Macs onto which I clone a fair number of git (mostly GitHub) repos. The Macs each have a number of iCloud drive synced directories (in fact I've gone all-in and am syncing Desktop and Documents).

I have tried to clone into the iCloud-synced directories. However, I have been having lots of problems with this. It seems very easy to get into a condition where iCloud (not git) gets so confused that one machine effectively stops syncing, even files that have nothing to do with the cloned directories, and even if I carefully re-sync each of the two clones to the exact same state. I don't know if the problem is files under .git/ or just something like race conditions between versions of the actual repo files.

I've tried to use Apple's various iCloud logging tools under brctl but that has generally not helped.

(Most of this has been posted as a question over on the main SO site: has anyone else seen this or anything like it?)

(This is somewhat different from this question which mostly seems to care about a single Mac with iCloud drive, and I don't think users in that situation would see the same issues that I am.)