Define a custom Git attribute to mark source files as generated

.gitattributes

@@ -1,6 +1,10 @@
 .gitattributes   export-ignore
 .hooks*          export-ignore
 
+# Custom attribute to mark sources as generated.
+# Do not perform whitespace checks.
+[attr]generated  whitespace=-tab-in-indent,-indent-with-non-tab
+
 bootstrap        crlf=input
 configure        crlf=input
 *.[1-9]          crlf=input

Source/.gitattributes

@@ -1,10 +1,17 @@
-# Preserve indentation style in generated code.
-cmCommandArgumentLexer.cxx      whitespace=-tab-in-indent,-indent-with-non-tab
-cmCommandArgumentLexer.h        whitespace=-tab-in-indent,-indent-with-non-tab
-cmDependsJavaLexer.cxx          whitespace=-tab-in-indent,-indent-with-non-tab
-cmDependsJavaLexer.h            whitespace=-tab-in-indent,-indent-with-non-tab
-cmExprLexer.cxx                 whitespace=-tab-in-indent,-indent-with-non-tab
-cmExprLexer.h                   whitespace=-tab-in-indent,-indent-with-non-tab
-cmFortranLexer.cxx              whitespace=-tab-in-indent,-indent-with-non-tab
-cmFortranLexer.h                whitespace=-tab-in-indent,-indent-with-non-tab
-cmListFileLexer.c               whitespace=-tab-in-indent,-indent-with-non-tab
+/cmCommandArgumentLexer.cxx        generated
+/cmCommandArgumentLexer.h          generated
+/cmCommandArgumentParser.cxx       generated
+/cmCommandArgumentParserTokens.h   generated
+/cmDependsJavaLexer.cxx            generated
+/cmDependsJavaLexer.h              generated
+/cmDependsJavaParser.cxx           generated
+/cmDependsJavaParserTokens.h       generated
+/cmExprLexer.cxx                   generated
+/cmExprLexer.h                     generated
+/cmExprParser.cxx                  generated
+/cmExprParserTokens.h              generated
+/cmFortranLexer.cxx                generated
+/cmFortranLexer.h                  generated
+/cmFortranParser.cxx               generated
+/cmFortranParserTokens.h           generated
+/cmListFileLexer.c                 generated