In Gitlab 8.10.7 the option to disable it has been deeply hidden away in 'Admin Area'(upper-right)»Settings(upper-right-dropdown)»'Account and Limit Settings'»'Gravatar enabled'»off. Since the option suggestedly must be changed from inside the web interface, leakage has already occurred once the settings change is made.
Numerous steps to disable leakage to http://gravatar.com in GitLab 8.10.7
It would be much easier to be able to do this without having to resort to a commandline tool, despite what's said in this discussion
Automatic updates can cause massive graphical user interface changes
Menu sidebars and settings screens continue to change and move around throughout various GitLab version upgrades (regardless of user/'skin' preference?).
Next to each clone url edit box, there are buttons to toggle between SSH (git:// protocol) and HTTP (http:// protocol). Older versions of GitLab
insisted on defaulting to SSH for logged in users, even though this choice could not work due to a non-existant SSH key. There was no easy way to change configuration option for this behaviour.
GitLab is a great tool for making Git repositories' information visible to the world, without having to depend on a third party cloud such as GitHub, Inc. Additionally it provides a database wrapping around each Git repository that can optionally be used to keep track of project issues and documentation (similar to Trac that is commonly used for SVN repositories), however they are not stored inside the repository and are therefore lost if the database is lost. GitLab doesn't implement some big features yet which could greatly expand its reach. Additionally its past update/upgrade management tends to take backwards compatibility lightly.