Several todos need to examine preferred content expressions to see if
any of the terms in them match some criteria. 

That includes:

* [[todo/sync_fast_import]]
* [[todo/faster_key_lookup_for_limits]]
* [[todo/skip_first_pass_in_git_annex_sync]]

Internally, preferred content expressions are compiled
into a `Matcher (AssumeNotPresent -> MatchInfo -> Annex Bool)`

The presence of the function there is a problem, because haskell does not
allow comparing functions for equality. So probably what is needed is
something that contains that function but also indicates which preferred
content term it's for. 

Or, perhaps, not the term, but the specific criteria needed by each such
todo.

> [[done]] --[[Joey]]
