Change location of .hg: mercurial equivalent of --separate-git-dir

[Michael Forbes]

What is the mercurial equivalent of git's --separate-git-dir?

My use case is allowing others to edit a working copy through Dropbox, Google Drive, etc. and then periodically being able to compare the state of that copy with my repository, optionally adding or committing their changes.

I don't want to store the .hg folder in the shared repo for risk of data corruption (if people simultaneously commit in several places and the drive share auto-manages conflicts IN the .hg repo).

I know I can use hg archive to update the shared working copy remotely from a repo, but don't know how to efficiently compare and commit changes made there.

Michael.