Is there any open source solution that will allow me to maintain a Mercurial and a Git repository and keep them fully synchronized?
This is what Kiln Harmony promises. I have worked on repository conversions and know tools that allow to do a conversion once. However, I have yet to find a tool that reliably (which excludes Dulwich + hg-git) keeps a Git and a Mercurial repository synchronized with every single push to either side. Reposurgeon would be another alternative, but it's not clear how continuous conversions would have to be approached and it is also subject to limitations of the tools it relies on (e.g. the Mercurial side has a very limited fast-import facility).
Is there anything that works out of the box and is available as open source?
Edit: so in response to the question in the comment:
Are there any features which are a "must" or "nice-to-have"? Should it run locally on your computer, or on the repository server? What OS must it support? Please read What is required for a question to contain "enough information"? and see if you can edit your question to improve it – which at the same time improves your chances for good and matching answers, Good luck!
- The only must-have features would be: that it works both ways and is reliable for production use.
- It should preferably run on the server that serves both the Git and the Mercurial repository, i.e. we can assume a centralized workflow. Given the nature of distributed version control systems this implies running locally on the machine with the repository (whether we call it server or not).
- Preferred OS would be an arbitrary Linux distribution, but any of the operating systems jointly supported by Git and Mercurial will also work. Since it's supposed to be a FLOSS solution, I'd expect to be able to adapt it where necessary.
- Preferably it should cost little to nothing. I'd rather contribute patches and defect reports than money.