tree 1fecddbe0c384ab077e5588321362a672f0e9fc4
parent 631a45f55b397090ad7d817a3c72041cfc3729f3
author Jeremy Stribling <strib@alum.mit.edu> 1503694327 -0700
committer Jeremy Stribling <strib@alum.mit.edu> 1503879289 -0700

plumbing: use `seen` map in tree walker

This helps avoids iterating down the same trees for every commit.  For
a big-ish repo with 35K objects (17K commits), this reduced the time
for calling `revlist.Objects` during a push (with 0 hashes to ignore)
from more than ten minutes to less than a minute.