[[!comment format=mdwn
 username="joey"
 subject="""comment 1"""
 date="2016-02-19T19:18:41Z"
 content="""
The metadata command is pretty complex. A batch interface would need to
cover both setting and getting. 

There are four different ways to change a value, so it would probably
make sense for the input to be of the form "file field=value"
or "file field+=value" or "file field-=value" or "file field?=value"

A field can have multiple values, including "". So, a batch interface
to querying the value would need to handle that in its output. Perhaps
json output?
"""]]
