GitLab

This reverts commit 3e33bb31.

The original commit broke the build (#612) when yaml-cpp is used as a git submodule.

* Move enable_testing() into proper place

* Added CMake's checks for C++11 standards

Raised minimal version of CMake to 3.1, since on old systems there no
decent compilers that supports c++11.

Closes #377.

* Externalize googletest project

Externalize gtest to avoid installation, fixes #539.

* Remove defined cmake_policies

CMP0012 - OLD marked as deprecated for >=cmake-3.1 and will be removed
CMP0015 - does not affect to build process
CMP0042 - already NEW for >=cmake-3.1

Fixes #505

* Fix compiling in Windows MSVC

Fix some virtual methods of NullEventHandler that were apparently
intended to overload base class methods, but did not. Add override
keyword to prevent these getting out of sync again.

Flag -n N repeats parsing N times.
Flag -c (--cache) caches the input in a string and uses that to parse.

On my Macbook Pro, reading from standard input incurs a bunch of locking
overhead, which complicates profiling and (IMO) adds noise to
results. This adds the option to read from a file, which doesn't incur
this overhead.

 - Adds 'std=c++11' compiler flags
 - Replaces boost::type_traits with std::type_traits
 - Replaces boost::shared_ptr with std::shared_ptr
 - Replaces std::auto_ptr with std::unique_ptr
 - Replaces raw pointers with std::unique_ptr in ptr_vector, ptr_stack, and SettingChanges
 - Replaces boost::noncopyable with deleted copy and assignment operators
 - Replaces boost::next with std::next
 - Replaces boost::enable_if with std::enable_if
 - Replaces boost::is_convertible with std::is_convertible
 - Replaces ptrdiff_t with std::ptrdiff_t
 - Replaces boost::iterator_facade and boost::iterator_adaptor with std::iterator, borrowing the 'proxy reference' technique from boost
 - Removes Boost dependency from CMakeLists
 - Formats changed files using clang-format

Add EmitterStyle, which will allow sequence or map style (i.e., flow or block) to be preserved between parsing and emitting

Added constructor to the Emitter with a stream, so you can write directly to a stream instead of our temp