offer tor
 onion:// urls,
 global option stating proxy url

document unlinked persistence

persistence editor
or rewind (easy: do not unlink previous file, allow to restore it)

config: 'pause'
 pause a feed (instead of removing it, that would lose bookmark)

template / global defaluts for feeds

crossbow-fetch
 ctrl+C should interrupt fetching, but saving what is done so far.
 Is this already the case?

collection of usable scripts (e.g. ytdl wrapper, ...)

tuning
 comparison study of sizes in outfmt.c

edit stored item
 I'd like to drop one video, so that I can realod it again.

escape sequence
 support ascii 7-13 perhaps?  Feature creep?

out of documentation:
 make enumerative conventions more consistent

review dependencies
 libmrss/libnxml is bloated (downloads, why?)
 unmaintained and not valgrind-clean.

security
 rss content is the attack vector
  - ensure length boundary on fields.
 mind allocated size
  - follow all the resource allocations that can be controlled by a feed xml.


 - mark things seen even if the processing failed.

Testing:

 * not updating the feed implies not updating the file.
   We save only if necessary.
 * outfmt is loaded once per feed
 * a corrupt persist file should prevent the whole handling of the feed,
   possibly including fetching.
 * verify issue: pretty format specification cannot be null-string
   (minor problem: why would you anyway?)
 * what if persist_dir/chdir do not exist?

* By specification, all fields of <item>s are optional.
  The logic should be:
   - if the item has a guid, use it.
   - else, if the item has a link, use it.
   - else the title
   - else use the incremental id (meaning that the fetch N forgets all the
	 items in the fetch N-1
