I've successfully used hg-git on something as large as Waterfox (slight irony there because Waterfox is a Firefox fork, and Firefox's canonical repository is a

I've successfully used hg-git on something as large as Waterfox (slight irony there because Waterfox is a Firefox fork, and Firefox's canonical repository is a Mercurial repository, though they also maintain a Git mirror). The import of something that large unfortunately took a few hours, and it's a bit annoying that under the hood hg-git needs to store both the native Git repository as well as a copy converted to a Mercurial repository, but other than that it works quite fine in day-to-day usage. And with smaller repo than something like Firefox's the above disadvantages are of course less to hardly noticeable.