Fix bug that caused importing from a special remote to repeatedly download
unchanged files when multiple files in the remote have the same content.
Unfortunately, there's really no good way to remove a uniqueness constraint
from a sqlite database. The best that can be done is to make a new table
and copy the data over. But that would require using persistent's
migrations or raw sql, and I don't want to do either.
Instead, a sledgehammer approach: Renamed .git/annex/cid to
.git/annex/cids. When the new database doesn't exist, it will be populated
from the git-annex branch.
Noting deletes the old database. Don't want to delete it out from under
some long-running git-annex process that might be using it. It could
eventually be deleted. But this is such a new feature, probably few repos
have the database in any case.
untested
This won't be super slow, but it does need to diff two likely large
trees, and since the git-annex branch rarely sits still, it will most
likely be run at the beginning of every import.
A possible speed improvement would be to only run this when the database
did not contain a ContentIdentifier. But that would only speed up
imports when there is no new version of a file on the special remote,
at most renames of existing files being imported.
A better speed improvement would be to record something in the git-annex
branch that indicates when an import has been run, and only do the diff
if the git-annex branch has record of a newer import than we've seen
before. Then, it would only run when there is in fact new
ContentIdentifier information available from a remote. Certianly doable,
but didn't want to complicate things yet.
Does not yet have a way to update with new information from the
git-annex branch, which will be needed when multiple repos are importing
from the same remote.
