Merge branch 'jk/fsck-on-diet'

"git fsck" failed to release contents of tree objects already used
from the memory, which has been fixed.

* jk/fsck-on-diet:
  parse_object_buffer(): respect save_commit_buffer
  fsck: turn off save_commit_buffer
  fsck: free tree buffers after walking unreachable objects

diff --cc builtin/fsck.c
Simple merge

diff --cc object.c
Simple merge