Enables up to 3 retries of uploading a single asset when encountering a network error or a HTTP 5xx error.
Bonus:
- simplifies ConcurrentUpload implementation
- support Go context cancellation
The `Request.GetBody` func allows the retry mechanism to reopen the file
that's being uploaded as the request body in case the body of the
previous request has already started to be read.
Hopefully fixes the error:
http2: Transport: cannot retry err [stream error: stream ID 1; REFUSED_STREAM]
after Request.Body was written; define Request.GetBody to avoid this error
Ref. d523dce5a7/http2/transport.go (L554)
Currently the mimecap package is an requirement to pass the test suite,
as we need /etc/mime.types to recognize the tar extension. A better idea
is to inline all of the basic test cases for the test suite.
Signed-off-by: Morten Linderud <morten@linderud.pw>
