I have a remote hg repository hosted on googlecode. Thus I don't have admin access to run e.g. lfconvert on it (as far as I know), and of course lfconvert can only be used on local repositories.
So, is there any way to a convert an googlecode hg repository to a largefile repository?
(one idea is to convert a local clone of the repo to a largefile repo and then push the changes to the "central" googlecode repo, but I fear trying that without knowing if it is a valid approach).
Using your idea to do a local conversion and push, you can take advantage of the 'reset' feature for your repositories:
Pushing the largefiles repository without reseting seems problematic because the largefiles repository is essentially a fork of the original one starting at the point the first largefile was committed.
If the push fails*, you can push the original clone and you'll be back where you started without any data loss. (One of the many advantages of DVCS. :-))
The big downside of course is that everybody who has ever cloned your project will now be working from a different fork of the repository. This is always a danger when you do anything involving changing history and is the motivation for Mercurial phases. If you want to be 'kinder', you can start a second project for the largefiles version and place a link at the original project cite describing the move.
[*] I can't figure out from Google Code's documentation whether the largefiles extension is supported. There is a reviewed feature request, but I couldn't find any mention of the request actually being implemented. The push failing would probably be a good indication that largefiles isn't supported though...