Add pretty_url and print_url
Add print_url to prun_refs
Repair DF conflicts when fetching with --prune

When a DF conflict occurs during a fetch, --prune should be able to fix
it. When fetching with --prune, the fetching process happens before
pruning causing the DF conflict to persist and report an error. This
patch prunes before fetching, thus correcting DF conflicts during a
fetch.

Signed-off-by: Tom Miller <jackerran@gmail.com>
Tested-by: Thomas Rast <tr@thomasrast.ch>