Gitlab guys found a working method to fight the git conflict on the CHANGELOG file: https://about.gitlab.com/2015/02/10/gitlab-reduced-merge-con...

Sumup:

> At GitLab we solved the above problem by adding a 100 lines with just a hyphen placeholder at the top of the changelog. People can insert their entry at a random location in the changelog. There is still a chance of conflict when two merge requests change the same line but it is greatly reduced. It looks a bit strange to have these empty lines on top so we added a comment to explain their purpose..