Use gitattributes custom merge driver in MRs
Description
Currently Gitlab reads .gitattributes file and use informations like "union" or "binary", but custom merge drivers are not used during merge requests (since they are defined in the gitconfig).
It can be a huge help to be able to use this git functionnality in gitlab MRs.
I explain a use case: I have project with a separate production and staging configs files, so I'll do a branch "prod" and an other "staging", with respective configs. Then the workflow is: dev on staging, and when it's ready for production, just do a merge request targeting prod branche. The problem is the configs files will conflicts during merge. One solution would be to put every configs files in the .gitattributes file, with custom merge driver, and do the merge locally, then push it on production. But we loose all the benefits of Gitlab MR interface, review etc ...
Maybe there is already some good practises, or a way to achieve that ? I didn't found one which fit well with the problem.
Proposal
Find a way to parse the config file in order to enable the custom driver functionality (maybe force the user to re-write it in some settings on the Gitlab interface ?).
Links / references
https://medium.com/@porteneuve/how-to-make-git-preserve-specific-files-while-merging-18c92343826b