To allow admin/owners to disable merge conflict resolution via UI either site-wide or per-project basis
Description
In reference to https://gitlab.com/gitlab-org/gitlab-ce/issues/21947 which raised issue on merge conflict via UI would merge the branch in reverse, this behavior is not favorable to some use cases as made apparent by the remarks in that issue ticket.
Proposal
While waiting for the final decision and solution on how address those concerns, I propose to have a switch to enable and disable the merge conflict UI, either site-wide by admin or per-project basis by each owner. If too much hassle to implement, I can make do with having a site-wide switch added into the gitlab.rb setting file.