v1.30.0

v1.30.0 Release

Bigtable:

BREAKING CHANGES:

• Async* functions in Table that took CompletionQueue& as a parameter
  have been removed. Users that need to update their code should use the
  identically named functions which do not require a CompletionQueue&. If
  users absolutely require a custom CompletionQueue, one can be supplied to
  the DataClient used to construct the Table, via
  ClientOptions::DisableBackgroundThreads(CompletionQueue const&).
  See #2567 for more details.

Storage:

BREAKING CHANGES:

• The usage of google::cloud::internal::ObjectReadSource has changed. If your
  tests mock how the library uses this class you may need to update your tests.
  We updated the mocking examples to guide you in
  changing the tests.

Other:

We have removed the super/ directory: google-cloud-cpp remains usable in
a super build for a larger project, but we do not believe these files add enough
value for the additional complexity. If you prefer to build all the dependencies
from source using CMake, we recommend you use a package manager, such as
vcpkg.

We have dropped support for Clang < 6.0: to support the latest Google Cloud
services we need a version of Protobuf that can compile all the .proto files
in https://github.com/googleapis/googleapis. At this time this requires
Protobuf >= 3.15, and these versions of Protobuf do not support older versions
of the Clang compiler.