The url log could have an url for a key, while the location log thinks it's
not present in the web. In this case, addurl --file url would not do
anything. Fixed it to re-add the web as a location.
I don't know how this situation could arise, but I saw it in the wild in
the conference_proceedings repo, affecting key
URL-s17806003--http://mirror.linux.org.au/pub/linux.conf.au/2014/Wednesday/53-Building_Effective_Alliances_around_the_Trans-Pacific_Partnershi-c0505b631127ccc67e38e637344d988e
Investigating the presence log, it looked like that key
was originally listed as present in the web, then in commit
56abf9e9f3e691ed9d83513037d4019313321ca3 someone else's git-annex
set it and some other things to not present in the web. It would be
interesting to know what that user did, but I doubt I'll be able to find
out. All I can tell from this investigation is that the inconsistency was
not introduced when originally addurl-ing the url.
git-annex allows managing files with git, without checking the file
contents into git. While that may seem paradoxical, it is useful when
dealing with files larger than git can currently easily handle, whether due
to limitations in memory, checksumming time, or disk space.
For documentation, see doc/ or <https://git-annex.branchable.com/>
589a048a7d