Dear Michal,

Thanks for all this. The feature looks great! One issue: I'm getting
corrupt output when using `--output=count` with "fold" filters:

~~~
jkr@ladybug [11:01AM] ~ $ notmuch search --output=recipients --output=count "tag:notmuch and date:today.." 
2	Jani Nikula <jani@nikula.org>
2	Michal Sojka <sojkam1@fel.cvut.cz>
1	David Edmondson <dme@dme.org>
9	notmuch@notmuchmail.org

jkr@ladybug [11:01AM] ~ $ notmuch search --output=recipients --output=count --filter-by=addrfold "tag:notmuch and date:today.."
2	Michal Sojka <0Fam1@fel.cvutH>
9	
1	David Edmondson <8dme.org>
2	Jani Nikula <jani@nikula.org>

jkr@ladybug [11:01AM] ~ $ notmuch search --output=recipients --output=count --filter-by=nameaddr "tag:notmuch and date:today.."
2	Jani Nikula <jani@nikula.org>
2	Michal Sojka <sojkam1@fel.cvut.cz>
1	David Edmondson <dme@dme.org>
9	notmuch@notmuchmail.org

jkr@ladybug [11:01AM] ~ $ notmuch search --output=recipients --output=count --filter-by=nameaddrfold "tag:notmuch and date:today.."
2	Jani Nikula <jani@nikula.org>
2	Michal Sojka <0V�	am1@fel.cvutH>
1	David Edmondson <8��	dme.org>
9
~~~

Not sure if this is expected behavior with the filtering mechanism in
its current state, but I wanted to call it to your attention if not.

Best,
Jesse