git-annex/doc/todo/export.mdwn

`git annex export` corresponding to import. This might be useful for eg,
datalad. There are some requests to make eg a S3 bucket mirror the
filenames in the git annex repository with incremental updates, 
which seem out of scope (and there are many tools to do stuff like that
search "deploy files to S3 bucket"), 
but something simpler like `git annex export` could be worth doing.

`git annex export --to remote files` would copy the files to the remote,
using the names in the working tree. For remotes like S3, it could add the
url of the exported file, so that another clone of the repo could use the
exported data.

Would this be able to reuse the existing `storeKey` interface, or would
there need to be a new interface in supported remotes?

--[[Joey]]

Work is in progress. Todo list:

* `git annex get --from export` works in the repo that exported to it,
  but in another repo, the export db won't be populated, so it won't work.
  Maybe just show a useful error message in this case?  
  However, exporting from one repository and then trying to update the
  export from another repository also doesn't work right, because the
  export database is not populated. So, seems that the export database needs
  to get populated based on the export log in these cases.
* Support export to aditional special remotes (S3 etc)
* Support export to external special remotes.