New port:devel/py-hg-evolve: Changeset Evolution with Mercurial

evolve is a Mercurial extension for faster and safer mutable history. It
implements the changeset evolution concept for Mercurial[1][2].

[1] https://www.mercurial-scm.org/doc/evolution/#
[2] https://pypi.org/project/hg-evolve/

Reviewed by: tcberner (mentor)
Approved by: arrowd (mentor)
Differential Revision: https://reviews.freebsd.org/D27150