hg-fast-export.sh from git-fast-export (available at repo.or.cz) works wonderfully. You need a local hg repository, but then you just dump to git and use your standard tools...
Even with distributed systems... The committer can be credited with some review and control, and the author with writing...
If the project containts GNU-formatted ChangeLog files, those are the place to look for who contributed which change...
Any hope of Fortran support?