Is there a way to use a Mercurial repository as Git submodule?

Using git-hg.

First, make sure there is a (non-Mercurial) git submodule under your main repository. If you don’t have other submodules yet, just create a dummy submodule for some library other than core-plot, for instance:

main-repo $ git submodule add https://repo.url.com/repo.git repo

Second, clone the core-plot library into some directory.

main-repo $ git-hg clone  https://code.google.com/p/core-plot/ core-plot

Add the new repo to the submodule list.

main-repo $ git submodule add ./core-plot core-plot
main-repo $ git commit -am "added core-plot submodule"

From now on, any clone from this repo will pull both repositories. (After submodule init and update).

Some problems I found out so far are:

• If you push to a bare, then the repo link and the directory will be created in the bare, but the repository will not be cloned inside it and others pulling from that bare will not be able to get the core-plot lib.
• If core-plot needs to be updated the one with the git-hg will have to git-hg pull.

The converse question git submodule from Hg repo? is also asked on StackOverflow. The best answer mentions projects hg-git and git-hg. Another related converse question is, How to deal with Git submodules on a repo that is converted to Mercurial.