Re: [PATCH v3] [GSOC] ref-filter: fix read invalid union member bug

Just a final sanity check.  Is this a recent breakage or was the
code introduced at cc72385f (for-each-ref: let upstream/push
optionally report the remote name, 2017-10-05) broken from the
beginning?

Well, The trigger condition is very special, but the bug was introduced
at that time. Let's see the "bug" example below.

I am wondering if it is easy to add a test to cover the codepath
that is affected by this change.

Thanks.

Well, because this bug must require that the seventeenth bit of
`used_atom.u` is not 0, it took me a long time to find this bug.
in `used_atom.u`, only the member "color" and "contents" which
size is bigger than 17 bytes, but "%(contents:trailer:only)" only fill
the 16th byte of `used_atom.u`.

"Fortunately", I found it.

git for-each-ref --format='%(color:#aa22ac)'

I will add test for it!

Thanks!
--
ZheNing Hu