Bigstore-compress filter is broken with S3 backend

[jansel]

I have not tested the other backends.

The first issue is the use of tempfile.TemporaryFile instead of tempfile.NamedTemporaryFile. The temporary file does not have a name on disk on most operating systems, which results in an error:

$ git bigstore push
pulling bigstore metadata...done
compressed!
Traceback (most recent call last):
  File "/home/jansel/testrepo/venv/bin/git-bigstore", line 87, in <module>
    args = parser.parse_args()
  File "/usr/lib/python2.7/argparse.py", line 1701, in parse_args
    args, argv = self.parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1733, in parse_known_args
    namespace, args = self._parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1942, in _parse_known_args
    stop_index = consume_positionals(start_index)
  File "/usr/lib/python2.7/argparse.py", line 1898, in consume_positionals
    take_action(action, args)
  File "/usr/lib/python2.7/argparse.py", line 1807, in take_action
    action(self, namespace, argument_values, option_string)
  File "/usr/lib/python2.7/argparse.py", line 1096, in __call__
    subnamespace, arg_strings = parser.parse_known_args(arg_strings, None)
  File "/usr/lib/python2.7/argparse.py", line 1733, in parse_known_args
    namespace, args = self._parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1942, in _parse_known_args
    stop_index = consume_positionals(start_index)
  File "/usr/lib/python2.7/argparse.py", line 1898, in consume_positionals
    take_action(action, args)
  File "/usr/lib/python2.7/argparse.py", line 1807, in take_action
    action(self, namespace, argument_values, option_string)
  File "/home/jansel/testrepo/venv/bin/git-bigstore", line 33, in __call__
    push()
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/bigstore/bigstore.py", line 246, in push
    backend.push(compressed_file, hexdigest, cb=ProgressPercentage(filename))
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/bigstore/backends/s3.py", line 35, in push
    self.s3_client.upload_file(file.name, self.bucket, self.get_remote_file_name(hash), Callback=cb)
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/boto3/s3/inject.py", line 106, in upload_file
    extra_args=ExtraArgs, callback=Callback)
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/boto3/s3/transfer.py", line 275, in upload_file
    future.result()
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/s3transfer/futures.py", line 73, in result
    return self._coordinator.result()
  File "/home/jansel/testrepo/venv/local/lib/python2.7/site-packages/s3transfer/futures.py", line 233, in result
    raise self._exception
OSError: [Errno 2] No such file or directory: '<fdopen>'

I fixed this issue on my fork, but bigstore-compress still seems buggy even after that. I observed the following behavior (with my partially fixed version):

1. echo '*.bin filter=bigstore-compress' >.gitattributes
2. dd if=/dev/zero of=test.bin bs=1M count=1
3. git a . && git commit -m 'test' && git bigstore push runs without error
4. git pull && git bigstore pull on another checkout results in a zero byte file instead of the expected 1M file