KWSys upstream added an attribute to export .gitattributes so that
importing snapshots into the sources of other projects would bring along
the attributes.  However, we don't want to export them from CMake.
Drop .gitattributes entries not relevant to CMake.

Add policy CMP0061 to maintain compatibility for existing projects.

Teach the legacy two-argument signature to use CMAKE_CONFIG_TYPE
from the environment only if it is non-empty.  This makes behavior
consistent with the main signature.

The find_package command, on Windows, has always searched build trees
recently visited by cmake-gui (or CMakeSetup at one time).  This was
done when the command was created with the intention of simplifying
workflows involving building multiple dependent projects.  However,
this behavior depends on recent developer interaction and therefore
can create different find results based on transient system states.
It can lead to surprising results and user confusion.

Since this behavior was first added CMake has gained many more search
options, better error messages when a package is not found, and a
package registry.  The latter in particular allows projects to make
their build trees available for dependent projects to find without
user intervention.  Therefore the originally intended workflow can
be achieved in other, more stable ways.

After the above evoluion of find_package we have now decided that
the magic search-where-cmake-gui-was behavior does more harm than
good.  Drop it.  We do not need a policy for this behavior change
because it only affects interactive use.

Thomas Herz authored May 08, 2015 and Brad King committed May 08, 2015

Fix a condition forgotten by commit b3de0dfe (Ninja: Use forward slashes
for any GCC on Windows, 2015-05-07).

The GNU 4.8 standard library's cstdio header is not aware that C++14
honors C11's removal of "gets" from stdio.h and results in an error:

  /.../include/c++/4.8/cstdio:120:11: error: no member named 'gets' in the global namespace

Detect this problematic case and default to using C++11 instead of
C++14 for building CMake itself.

Use the KWSys Process "MergeOutput" option to give the child process
the same pipe (or file) for both stdout and stderr.  This allows
natural merging of stdout and stderr together instead of merging
on arbitrary buffered read boundaries as before.

Thomas Herz authored May 07, 2015 and Brad King committed May 07, 2015

Since commit v2.8.11~213^2 (Ninja: Avoid LNK1170 linker error, 2013-02-01)
we generate linker response files with "$in_newline" to support a large
number of object files with the MS link.exe tool.  However, the GNU linker
on Windows does not understand the newline endings that Ninja puts in the
response files.  Switch back to "$in" for that case.

Thomas Herz authored May 07, 2015 and Brad King committed May 07, 2015

Any GCC compiler on a Windows host needs forward slashes, not just
those built for MinGW.

Check for CMAKE_COMPILER_IS_MINGW only after enabling a language when it
might actually be set.  Previously this worked by accident because the
check for working compiler or a second language enabled would cause the
code path to be taken.

Store UsingMinGW as an instance member of cmGlobalNinjaGenerator so that
it is reset on each reconfigure.  Otherwise cmake-gui cannot switch
between build trees for MinGW or non-MinGW tools.

Revert the refactoring by commit v2.8.11~105^2~1 (Ninja: use MinGW
generator code in EnableLanguage, 2013-03-09) and move the MinGW-
specific logic back to the "MinGW Makefiles" generator.  Instead teach
the platform information modules for GNU and MSVC on Windows to set the
preferred RC compiler just before enabling the RC language.  This way
we choose the RC compiler based on the C/C++ toolchain that is actually
enabled.

Robert Goulet authored May 01, 2015 and Brad King committed May 06, 2015

Add a CMAKE_VS_INCLUDE_INSTALL_TO_DEFAULT_BUILD variable to control
this behavior.

Hide the detail that it is a std::map.

Policies are no longer defined at runtime.

It would be possible to implement this with an XMacro and switch
statement, but every codepath currently would still return WARN.

Use it to populate the policy enum.