For advanced Git users, when using Mercurial, you loose the Git index (but not what you usually do with it) and you gain very interesting features, like for example long-term named branches, safe distributed history edition (phases, obsolete changesets, evolve extension) and the command `hg absorb` (automatic injection of uncommitted changes into prior commits in a PR).
### Warning! Gitlab does not natively support Mercurial!
For now, we'll have to use a Mercurial extension (hg-git) and it won't be as nice as if we could use a platform natively supporting Mercurial (as for example Bitbucket).
But [Heptapod (Gitlab with Mercurial support)](https://octobus.net/blog/2018-09-18-heptapod-announce.html) is coming.
But there is now [Heptapod (Gitlab with Mercurial support)](https://heptapod.net/).