gitattributes: use clang-format for all source files

Also ignore some files which should not be formatted.

.gitattributes

@@ -6,14 +6,26 @@ newalpha         crlf=input
 newversion       crlf=input
 pre-commit       crlf=input
 
-*.c              whitespace=tab-in-indent
-*.h              whitespace=tab-in-indent
-*.cxx            whitespace=tab-in-indent
-*.hxx            whitespace=tab-in-indent
-*.txx            whitespace=tab-in-indent
-*.txt            whitespace=tab-in-indent
-*.cmake          whitespace=tab-in-indent
+# Custom attribute to mark sources as using our C code style.
+[attr]our-c-style  whitespace=tab-in-indent,-blank-at-eol  format.clang-format=8
+
+*.c              our-c-style
+*.h              our-c-style
+*.cpp            our-c-style
+*.cxx            our-c-style
+*.hxx            our-c-style
+*.txx            our-c-style
+*.mm             our-c-style
+*.glsl           whitespace=tab-in-indent,-blank-at-eol
+*.txt            whitespace=tab-in-indent,-blank-at-eol
+*.cmake          whitespace=tab-in-indent,-blank-at-eol
 
 *.sha512         eol=lf
 
 *.md             whitespace=tab-in-indent conflict-marker-size=30
+
+# Third party code.
+Utilities/KWIML/**  -format.clang-format
+Utilities/KWSys/**  -format.clang-format
+Utilities/MetaIO/** -format.clang-format
+ThirdParty/**       -format.clang-format

Common/Core/.gitattributes

+vtkMersenneTwister_Private.cxx            -format.clang-format
 vtkWin32OutputWindowProcessEncodedData.c  -format.clang-format

Domains/Chemistry/.gitattributes

+vtkBlueObeliskDataInternal.h  -format.clang-format

Filters/Core/.gitattributes

+# Generated by vtkStreamingTessellatorGenerator.py
+vtkStreamingTessellator.cxx  -format.clang-format

IO/Import/.gitattributes

+mtlsyntax.*             -format.clang-format
+vtkVRMLImporter_Yacc.h  -format.clang-format

Rendering/Core/.gitattributes

+vtkPythagoreanQuadruples.h  -format.clang-format

Rendering/FreeType/fonts/.gitattributes

+face_*  -format.clang-format

Rendering/RayTracing/.gitattributes

+RTWrapper/**    -format.clang-format

Wrapping/Tools/.gitattributes

+# Cached generated code.
+lex.yy.c        -format.clang-format
+vtkParse.tab.c  -format.clang-format