[[!comment format=mdwn
 username="joey"
 subject="""comment 3"""
 date="2016-01-25T17:51:25Z"
 content="""
Wait, you can't add a file to git that's not present, so even if addurl did
support largefiles for --fast and --relaxed, all it could do if the file
was not large was error out, because it wouldn't have downloaded the
content to add to git in the first place!

Now, as to some plumbing to check if an expression matches
some data, it's a good idea. Implementing it without adding a lot of
complexity may be tricky though. In particular something like `limitSize`
can't currently error out, which is important so that matching preferred
content never crashes git-annex.. but it needs to if the size is not provided
in this other use case.

What I think I could do is add a new data type to MatchInfo, something
like:

	MatchingInfo (Maybe FilePath) (Maybe FileSize) (Maybe Key)

And then in terminals like `limitSize`, when a MatchingInfo is provided,
have it error out if size is not provided.

The command-line interface for this would be sufficiently complicated
that it might be best to go with a full json input for batch mode.
User needs to provide the expression, and any/all of filepath, filesize,
key, and in the future perhaps other info (mime type etc). 

Maybe  batch mode wouldn't be needed though; the command should not need
to spin up any git helper processes at all to check such an expression and so
should run pretty fast.
"""]]
