They do have a ton of tests actually. In their defence, if this task is doing Git things then just killing it when it goes badly is probably the best you can do. Git itself is quite buggy if you stray from the most basic setup. I've had it almost completely destroy my .git directory in the past when using submodules.

On the other hand, Gitlab itself is an enormous entirely untyped Ruby monster, with extremely difficult to follow code. Not in terms of individual functions - except for the lack of types mean you can't really know what they do, they are quite clear and well written. The issue is the control flow between parts of the system. It's difficult to know what calls what, so I'm not surprised they occasionally have to give up.

I had a play with Deno's Fresh web framework recently (Typescript/TSX but mainly server rendered). IMO it's light years ahead of other solutions.

You get full amazing Typescript typing, including in templates (unlike Go for example), but unlike React you don't have to deal with JavaScript tooling or complex client side state management. It's a real breath of fresh air. (Ha that wasn't even intentional.)