Retry (or resume) when encountering download errors about git-lfs

[technoweenie]

It simply writes to STDERR now. There's no actual retry yet. Right now it just writes the pointer file out to disk if it can't get the media file. But I agree it should retry during the git smudge command.

[85danf]

@technoweenie @rubyist , I'd just like to add it seems like a bug to me - writing the pointer file (which has the exact name as the file itself) can be misleading: i.e. I expect the file to be there and it is - but the content is wrong, now I have to backtrack and understand what messed up (think about a CI server failing a build over this or worse - packaging a release with bad content).
you should not write the pointer if the get failed in my opinion.

[technoweenie]

We have some retries now.