[[!comment format=mdwn
 username="http://joeyh.name/"
 ip="209.250.56.7"
 subject="comment 3"
 date="2014-08-12T18:58:49Z"
 content="""
I think that to support this, the annex.largefiles preferred content expression would need to be supplimented with checks not available in the normal preferred content language. 

In general, it's important that preferred content expressions be able to be evaluated without having the file content locally available, and it needs to be possible for a repository to evaluate the preferred content of a sibling repository and know if its sibling wants a file. These things would be defeated by any mime-based expressions. So such expressions should only be available in annex.largefiles and not in other preferred content expressions.

Calling out to `file` or some other external program could work. Although speed can be important. If the assistant is seeing a file frequently change, it's not ideal for it to be repeatedly running `file` on it. There does not seem to be a pure haskell MIME type checking library available at present.
"""]]
