Protobuf-py3

General
* Fixed invalid link to gtest in autogen.sh

General
* This fork is now diverged from one provided by Google in the sense that
versioning is different.
However it still can be used as a drop-in replacement since it will support
all the feature of the most recent official release.
This fork should be considered deprecated once Google provide compatibility
with Python 3 in the official repository.
* Apply change r524 from the official repo
* Apply change r525 from the official repo

Python
* Fixed bug where the module sys is used without being imported
* Fixed bug where type is encoded into bytes in Python 3 while it should be
a string.

General
* New notion "import public" that allows a proto file to forward the content
it imports to its importers. For example,
// foo.proto
import public "bar.proto";
import "baz.proto";

// qux.proto
import "foo.proto";
// Stuff defined in bar.proto may be used in this file, but stuff from
// baz.proto may NOT be used without importing it explicitly.
This is useful for moving proto files. To move a proto file, just leave
a single "import public" in the old proto file.
* New enum option "allow_alias" that specifies whether different symbols can
be assigned the same numeric value. Default value is "true". Setting it to
false causes the compiler to reject enum definitions where multiple symbols
have the same numeric value.
Note: We plan to flip the default value to "false" in a future release.
Projects using enum aliases should set the option to "true" in their .proto
files.

C++
* New generated method set_allocated_foo(Type* foo) for message and string
fields. This method allows you to set the field to a pre-allocated object
and the containing message takes the ownership of that object.
* Added SetAllocatedExtension() and ReleaseExtension() to extensions API.
* Custom options are now formatted correctly when descriptors are printed in
text format.
* Various speed optimizations.

Java
* Comments in proto files are now collected and put into generated code as
comments for corresponding classes and data members.
* Added Parser to parse directly into messages without a Builder. For
example,
Foo foo = Foo.PARSER.ParseFrom(input);
Using Parser is ~25% faster than using Builder to parse messages.
* Added getters/setters to access the underlying ByteString of a string field
directly.
* ByteString now supports more operations: substring(), prepend(), and
append(). The implementation of ByteString uses a binary tree structure
to support these operations efficiently.
* New method findInitializationErrors() that lists all missing required
fields.
* Various code size and speed optimizations.

Python
* Added support for dynamic message creation. DescriptorDatabase,
DescriptorPool, and MessageFactory work like their C++ couterparts to
simplify Descriptor construction from *DescriptorProtos, and MessageFactory
provides a message instance from a Descriptor.
* Added pickle support for protobuf messages.
* Unknown fields are now preserved after parsing.
* Fixed bug where custom options were not correctly populated. Custom
options can be accessed now.
* Added EnumTypeWrapper that provides better accessibility to enum types.
* Added ParseMessage(descriptor, bytes) to generate a new Message instance
from a descriptor and a byte string.

C++
* Fixed the frendship problem for old compilers to make the library now gcc 3
compatible again.
* Fixed vcprojects/extract_includes.bat to extract compiler/plugin.h.

Java
* Removed usages of JDK 1.6 only features to make the library now JDK 1.5
compatible again.
* Fixed a bug about negative enum values.
* serialVersionUID is now defined in generated messages for java serializing.
* Fixed protoc to use java.lang.Object, which makes "Object" now a valid
message name again.

Python
* Experimental C++ implementation now requires C++ protobuf library installed.
See the README.txt in the python directory for details.

General
* The RPC (cc|java|py)_generic_services default value is now false instead of
true.
* Custom options can have aggregate types. For example,
message MyOption {
optional string comment = 1;
optional string author = 2;
}
extend google.protobuf.FieldOptions {
optional MyOption myoption = 12345;
}
This option can now be set as follows:
message SomeType {
optional int32 field = 1 [(myoption) = { comment:'x' author:'y' }];
}

C++
* Various speed and code size optimizations.
* Added a release_foo() method on string and message fields.
* Fixed gzip_output_stream sub-stream handling.

Java
* Builders now maintain sub-builders for sub-messages. Use getFooBuilder() to
get the builder for the sub-message "foo". This allows you to repeatedly
modify deeply-nested sub-messages without rebuilding them.
* Builder.build() no longer invalidates the Builder for generated messages
(You may continue to modify it and then build another message).
* Code generator will generate efficient equals() and hashCode()
implementations if new option java_generate_equals_and_hash is enabled.
(Otherwise, reflection-based implementations are used.)
* Generated messages now implement Serializable.
* Fields with [deprecated=true] will be marked with Deprecated in Java.
* Added lazy conversion of UTF-8 encoded strings to String objects to improve
performance.
* Various optimizations.
* Enum value can be accessed directly, instead of calling getNumber() on the
enum member.
* For each enum value, an integer constant is also generated with the suffix
_VALUE.

Python
* Added an experimental C++ implementation for Python messages via a Python
extension. Implementation type is controlled by an environment variable
PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION (valid values: "cpp" and "python")
The default value is currently "python" but will be changed to "cpp" in
future release.
* Improved performance on message instantiation significantly.
Most of the work on message instantiation is done just once per message
class, instead of once per message instance.
* Improved performance on text message parsing.
* Allow add() to forward keyword arguments to the concrete class.
E.g. instead of
item = repeated_field.add()
item.foo = bar
item.baz = quux
You can do:
repeated_field.add(foo=bar, baz=quux)
* Added a sort() interface to the BaseContainer.
* Added an extend() method to repeated composite fields.
* Added UTF8 debug string support.

General
* Parsers for repeated numeric fields now always accept both packed and
unpacked input. The [packed=true] option only affects serializers.
Therefore, it is possible to switch a field to packed format without
breaking backwards-compatibility -- as long as all parties are using
protobuf 2.3.0 or above, at least.
* The generic RPC service code generated by the C++, Java, and Python
generators can be disabled via file options:
option cc_generic_services = false;
option java_generic_services = false;
option py_generic_services = false;
This allows plugins to generate alternative code, possibly specific to some
particular RPC implementation.

protoc
* Now supports a plugin system for code generators. Plugins can generate
code for new languages or inject additional code into the output of other
code generators. Plugins are just binaries which accept a protocol buffer
on stdin and write a protocol buffer to stdout, so they may be written in
any language. See src/google/protobuf/compiler/plugin.proto.
**WARNING**: Plugins are experimental. The interface may change in a
future version.
* If the output location ends in .zip or .jar, protoc will write its output
to a zip/jar archive instead of a directory. For example:
protoc --java_out=myproto_srcs.jar --python_out=myproto.zip myproto.proto
Currently the archive contents are not compressed, though this could change
in the future.
* inf, -inf, and nan can now be used as default values for float and double
fields.

C++
* Various speed and code size optimizations.
* DynamicMessageFactory is now fully thread-safe.
* Message::Utf8DebugString() method is like DebugString() but avoids escaping
UTF-8 bytes.
* Compiled-in message types can now contain dynamic extensions, through use
of CodedInputStream::SetExtensionRegistry().
* Now compiles shared libraries (DLLs) by default on Cygwin and MinGW, to
match other platforms. Use --disable-shared to avoid this.

Java
* parseDelimitedFrom() and mergeDelimitedFrom() now detect EOF and return
false/null instead of throwing an exception.
* Fixed some initialization ordering bugs.
* Fixes for OpenJDK 7.

Python
* 10-25 times faster than 2.2.0, still pure-Python.
* Calling a mutating method on a sub-message always instantiates the message
in its parent even if the mutating method doesn't actually mutate anything
(e.g. parsing from an empty string).
* Expanded descriptors a bit.