Thanks a lot for this contribution - plenty of issues showed up in the past because of this !

There are sill more somewhere but we haven't found them yet.

Gitdb is the other location which deals with files, sometimes indirectly through the use of smmap. I would suspect smmap, as each mmap opened on a file will effectively duplicate the file-handle. If the original is not closed, there would be a leak. It's just a guess of mine, which would need to be verified.