Since heptapod!289 was merged, we ship all necessary code to stop converting native Mercurial repositories to Git. This is controlled by the `hg_with_git?` method of `HgitalyRepository` which currently always returns `true` in the main development branch and is tied to the `:hg_fully_native` flag in the experimental `hgitaly2` branch. Since the `:hg_fully_native` feature flag is about to become `true` by default, we won't be able to rely on it to proceed further. As just discussed with @raphael.gomes, we should introduce a new feature flag, e.g, `:hg_without_git`, defaulting to `false`. Perhaps with another one for re-enabling the Git conversion on a single project if the feature flag is globally set to `true`, as we've done for `:hg_fully_native`. - [x] definition of the feature flag(s) and usage in `hg_with_git?` in conjunction with `:hg_fully_native` - [x] provide a way to resync the auxiliary Git repository without side effects when opting out. Ideally should be exposed in Project Repository settings. Perhaps also rake task to resync several (or all) of them?