git: actually copy treemanifest instances in .copy() (
issue6398)
The implementation here is so simple I honestly have no idea why I
didn't do it at the time. Hopefully there's not some nuance past-me
forgot to write down.
Differential Revision: https://phab.mercurial-scm.org/D8993
Greg Ward, author of the original bfiles extension
Na'Tosha Bard of Unity Technologies
Fog Creek Software
Special thanks to the University of Toronto and the UCOSP program