I took another look at this and tried to simplify things. The main
points were:

 - there is a real bug
 - it can be fixed by relying on get_reference() more
    - but there was some discussion about what get_reference() does, so
      I added some documentation first

Hopefully those main points were adequately conveyed in the new commit
messages, and I didn't oversimplify things.

There was some discussion about whether get_reference() should treat
corrupt objects as missing. After some thought, I think the best
argument for doing so is that this has been its behavior for some time,
and have wrote that in the first commit.

Jonathan Tan (2):
  revision: document get_reference()
  revision: un-regress --exclude-promisor-objects

 revision.c               | 12 +++++++++++-
 t/t0410-partial-clone.sh | 12 +++---------
 2 files changed, 14 insertions(+), 10 deletions(-)

-- 
2.25.0.rc1.283.g88dfdc4193-goog