[[!comment format=mdwn
 username="joey"
 subject="""comment 1"""
 date="2016-12-13T14:40:02Z"
 content="""
I thought this would involve the journal, but it seems not; same
behavior occurs if the journal is committed after each metadata change.

Looking at the new metadata value in the case where a and c both get set,
it is:

	MetaData (fromList [(MetaField "f",fromList [MetaValue (CurrentlySet True) "a",MetaValue (CurrentlySet False) "c"])])

That is supposed to unset c, with the CurrentlySet False, but instead c
remains set somehow.

Aha, the use of `addMetaData'` causes the bug. That reuses the same
timestamp, and indeed the same timestamp is used for all the batch
changes. With the same timestamp for the log line that sets c as the line
that removes it, it's indeterminite which line will be acted on first, and
so the removal can be processed before the addition, leaving c "stuck".

Fixing..
"""]]