http://e26whn2524322mkxb3cbyk27ev2ihhq2biz35hty7gzgsyrwrygq27yd.onion/posts/documentation/linux/745-allowing-your-internal-search-engine-to-index-gitlab-issues-commits-and-wiki-pages.html
It's not just on-prem Gitlab either, it also affects their cloud offering. Search within Gitlab is excellent, but this is of little use if you have things spread across systems and want to search from a single central point (to be fair to Gitlab, their idea is that everything you do should be within their solution, but life rarely actually works that way).