"checkPresent baser" was wrong; the baser has a dummy checkPresent action
not the real one. So, to fix this, we need to call preparecheckpresent to
get a checkpresent action that can be used to check if chunks are present.
Note that, for remotes like S3, this means that the preparer is run,
which opens a S3 handle, that will be used for each checkpresent of a
chunk. That's a good thing; if we're resuming an upload that's already many
chunks in, it'll reuse that same http connection for each chunk it checks.
Still, it's not a perfectly ideal thing, since this is a different http
connection that the one that will be used to upload chunks. It would be
nice to improve the API so that both use the same http connection.
This needs a patch to git to cause the git-annex completion to be
auto-loaded when completing "git annex <tab>". Otherwise, it will only
load when "git-annex" is tab completed. Once loaded, it works for both
uses. I've submitted the git patch to the git mailing list.
The branch needs to be created when merging from the remote in sync,
since we diff between it and the remote's sync branch. But git annex merge
should not be creating sync branches.
