The Mercurial Wiki for hg-fastimport documents other repositories from which this project was forked from. It seems to have been forked a fair bit as maintainers changet support newer Mercurial releases.
This version adds support for Mercurial 5.6+ and Python 3.6+. It also optionally supports the use of SQLite if available as that is faster for handling blobs than the filesystem.
As Mercurial officially supports Python 2.7 and py-fastimport has dropped support for Python 2, hg-fastimport now embeds a version of py-fastimport that still supports Python 2.7. As such, this extension no longer has any dependencies other than Mercurial and of course Python.
Unlike the Mercurial convert extension, this extension maps git branches to Mercurial named branches rather than bookmarks. This does mean that a commit can not have more than two parents, so you cannot use this plugin to import a repository that has had an octopus merge.