lfs: avoid quadratic performance in processing server responses
This is also adapted from the Facebook repo[1]. Unlike there, we were already
reading the download stream in chunks and immediately writing it to disk, so we
basically avoided the problem on download. There shouldn't be a lot of data to
read on upload, but it's better to get rid of this pattern.
[1] https://github.com/facebookexperimental/eden/commit/
82df66ffe97e21f3ee73dfec093c87500fc1f6a7
Differential Revision: https://phab.mercurial-scm.org/D7882
#require no-pure
A script to generate nasty diff worst-case scenarios:
$ cat > s.py <<EOF
> import random
> for x in range(100000):
> print
> if random.randint(0, 100) >= 50:
> x += 1
> print(hex(x))
> EOF
$ hg init a
$ cd a
Check in a big file:
$ "$PYTHON" ../s.py > a
$ hg ci -qAm0
Modify it:
$ "$PYTHON" ../s.py > a
Time a check-in, should never take more than 10 seconds user time:
$ hg ci --time -m1
time: real .* secs .user [0-9][.].* sys .* (re)