Correctly preserve "not set anywhere" TensorOptions when merging. (#33510)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33510
Previously, we would fill in TensorOption with defaults whenever an
item was missing from both the left and right side of the merge. This
is morally incorrect: if we don't have an item on the left or right,
we should keep the entry empty (so the downstream user can apply
the appropriate defaulting rule).
I don't think this caused any bugs, but I noticed this error when
working on a later patch in my diff stack.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D20001775
Pulled By: ezyang
fbshipit-source-id: 88139fc268b488cd1834043584a0d73f46c8ecaa
