Implement storage methods in the Azure provider.

Implement storage methods in the Azure provider.

This branch implements 4 storage-related methods in the Azure provider: azureStorage.Get, azureStorage.List, azureStorage.Put and azureStorage.Remove.  The implementations are rather straightforward: simple calls to gwacl with the occasional formatting of the returned data.

Some abstractions (like the storageContext interface) were added for the sole purpose of being able to do some dependency injection in the tests.

https://code.launchpad.net/~rvb/juju-core/az-storage/+merge/170622

(do not edit description out of merge proposal)

[rvb, 2013-06-24 10:24:08]

Please take a look.

[wallyworld, 2013-06-24 12:23:07]

LGTM

https://codereview.appspot.com/10478045/diff/1/environs/azure/storage.go
File environs/azure/storage.go (right):

https://codereview.appspot.com/10478045/diff/1/environs/azure/storage.go#newc...
environs/azure/storage.go:56: return nil, errors.NotFoundf("file '%s' not
found", name)
minor fix - use %q instead of '%s'

[jtv.canonical, 2013-06-24 13:08:15]

I'm approving, but with two notes.

https://codereview.appspot.com/10478045/diff/1/environs/azure/storage_test.go
File environs/azure/storage_test.go (right):

https://codereview.appspot.com/10478045/diff/1/environs/azure/storage_test.go...
environs/azure/storage_test.go:165: err := azStorage.Put(filename,
strings.NewReader(blobContent), 10)

In TestPut, you Put() a blobContent of 9 bytes, with a length of 10 bytes.  That
number seems a little meaningless.  Would it make more sense to pass
len(blobContent) instead, like you would on a normal call?

https://codereview.appspot.com/10478045/diff/1/environs/azure/storage_test.go...
environs/azure/storage_test.go:187: func (StorageSuite)
TestRemoveNonExistantBlobSucceeds(c *C) {

Would be worth testing also that Remove() still fails if it hits a non-404
error.  We wouldn't want to go around hiding weird bugs that result in quiet
failure of incorrect deletions!

[jtv.canonical, 2013-06-24 13:14:56]

LGTM ← I'm guessing that I vote by starting my message with that little
celebration of hacker elitism.  Not finding it in the help documentation.

[rvb, 2013-06-24 13:21:59]

Both good points, fixed!

Thanks for the review.