ENH: Support documents for better code formatting conformance

Use Update C++/C attributes for itk style conformance.

Add script to assist with running clang-format on topic-branches Derived
from
https://github.com/Kitware/CMake/blob/master/Utilities/Scripts/clang-format.bash

Define the .clang-format config file to enforce style that is compatible
with automated enforcement.

A code style that can be automatically enforced and integrated
with IDE's for automated conformance.

The code style options are defined at
https://clang.llvm.org/docs/ClangFormatStyleOptions.html

.clang-format

@@ -1,26 +1,38 @@
+## This config file is only relevant for clang-format version 8.0.0
+## See: https://clang.llvm.org/docs/ClangFormatStyleOptions.html for details of each option
+##
+## The clang-foramt binaries can be downloaded as part of the clang binar distributions
+## from http://releases.llvm.org/download.html
 ---
+# This configuration requires clang-format version 8.0.0 exactly.
+#  BasedOnStyle: Mozilla
 Language:        Cpp
-BasedOnStyle:  Mozilla
 AccessModifierOffset: -2
 AlignAfterOpenBracket: Align
 AlignConsecutiveAssignments: false
 AlignConsecutiveDeclarations: true
-AlignEscapedNewlines: Left
+AlignEscapedNewlines: Right
 AlignOperands:   true
 AlignTrailingComments: true
+# clang 9.0 AllowAllArgumentsOnNextLine: true
+# clang 9.0 AllowAllConstructorInitializersOnNextLine: true
 AllowAllParametersOfDeclarationOnNextLine: false
 AllowShortBlocksOnASingleLine: false
 AllowShortCaseLabelsOnASingleLine: false
 AllowShortFunctionsOnASingleLine: Inline
+# clang 9.0 AllowShortLambdasOnASingleLine: All
+# clang 9.0 features AllowShortIfStatementsOnASingleLine: Never
 AllowShortIfStatementsOnASingleLine: false
 AllowShortLoopsOnASingleLine: false
-AlwaysBreakAfterDefinitionReturnType: TopLevel
+AlwaysBreakAfterDefinitionReturnType: None
 AlwaysBreakAfterReturnType: All
 AlwaysBreakBeforeMultilineStrings: false
 AlwaysBreakTemplateDeclarations: Yes
 BinPackArguments: false
 BinPackParameters: true
+BreakBeforeBraces: Custom
 BraceWrapping:
+  # clang 9.0 feature AfterCaseLabel:  false
   AfterClass:      true
   AfterControlStatement: true
   AfterEnum:       true
@@ -32,20 +44,23 @@ BraceWrapping:
   AfterExternBlock: true
   BeforeCatch:     true
   BeforeElse:      true
-  IndentBraces:    true
+## This is the big change from historical ITK formatting!
+# Historically ITK used a style similar to https://en.wikipedia.org/wiki/Indentation_style#Whitesmiths_style
+# with indented braces, and not indented code.  This style is very difficult to automatically
+# maintain with code beautification tools.  Not indenting braces is more common among
+# formatting tools.
+  IndentBraces:    false
   SplitEmptyFunction: false
   SplitEmptyRecord: false
-  SplitEmptyNamespace: true
+  SplitEmptyNamespace: false
 BreakBeforeBinaryOperators: None
-BreakBeforeBraces: GNU
-BreakBeforeInheritanceComma: true
+#clang 6.0 BreakBeforeInheritanceComma: true
 BreakInheritanceList: BeforeComma
 BreakBeforeTernaryOperators: true
-BreakConstructorInitializersBeforeComma: true
+#clang 6.0 BreakConstructorInitializersBeforeComma: true
 BreakConstructorInitializers: BeforeComma
 BreakAfterJavaFieldAnnotations: false
 BreakStringLiterals: true
-# ColumnLimit:     200
 ColumnLimit:     120
 CommentPragmas:  '^ IWYU pragma:'
 CompactNamespaces: false
@@ -71,12 +86,12 @@ IncludeCategories:
     Priority:        1
 IncludeIsMainRegex: '(Test)?$'
 IndentCaseLabels: true
-IndentPPDirectives: None
+IndentPPDirectives: AfterHash
 IndentWidth:     2
 IndentWrappedFunctionNames: false
 JavaScriptQuotes: Leave
 JavaScriptWrapImports: true
-KeepEmptyLinesAtTheStartOfBlocks: false
+KeepEmptyLinesAtTheStartOfBlocks: true
 MacroBlockBegin: ''
 MacroBlockEnd:   ''
 MaxEmptyLinesToKeep: 2
@@ -92,13 +107,16 @@ PenaltyBreakFirstLessLess: 120
 PenaltyBreakString: 1000
 PenaltyBreakTemplateDeclaration: 10
 PenaltyExcessCharacter: 1000000
-PenaltyReturnTypeOnItsOwnLine: 0
-PointerAlignment: Left
+PenaltyReturnTypeOnItsOwnLine: 200
+PointerAlignment: Middle
 ReflowComments:  true
-SortIncludes:    true
-SortUsingDeclarations: true
+# We may want to sort the includes as a separate pass
+SortIncludes:    false
+# We may want to revisit this later
+SortUsingDeclarations: false
 SpaceAfterCStyleCast: false
-SpaceAfterTemplateKeyword: false
+# SpaceAfterLogicalNot: false
+SpaceAfterTemplateKeyword: true
 SpaceBeforeAssignmentOperators: true
 SpaceBeforeCpp11BracedList: false
 SpaceBeforeCtorInitializerColon: true
@@ -113,6 +131,9 @@ SpacesInCStyleCastParentheses: false
 SpacesInParentheses: true
 SpacesInSquareBrackets: false
 Standard:        Cpp11
+StatementMacros:
+  - Q_UNUSED
+  - QT_REQUIRE_VERSION
 TabWidth:        2
 UseTab:          Never
 ...

.gitattributes

@@ -0,0 +1,46 @@
+.git*            export-ignore
+.hooks*          export-ignore
+.mailmap         export-ignore
+
+*.bat           -crlf
+*.bin           -crlf
+*.jpg           -crlf
+*.mha           -crlf
+*.pdf           -crlf
+*.png           -crlf
+*.raw           -crlf
+*.sh             crlf=input
+*.sh.in          crlf=input
+configure        crlf=input
+cvsrmvend        crlf=input
+imcp             crlf=input
+imglob           crlf=input
+imln             crlf=input
+immv             crlf=input
+imrm             crlf=input
+imtest           crlf=input
+install-sh       crlf=input
+newalpha         crlf=input
+newversion       crlf=input
+remove_ext       crlf=input
+vxl_doxy.pl      crlf=input
+zap.pl           crlf=input
+
+
+# Custom attribute to mark sources as using our C++/C code style.
+[attr]our-c-style  whitespace=tab-in-indent,no-lf-at-eof  hooks.style=KWStyle,clangformat
+
+*.c              our-c-style
+*.h              our-c-style
+*.cxx            our-c-style
+*.hxx            our-c-style
+*.txx            our-c-style
+*.txt            whitespace=tab-in-indent,no-lf-at-eof
+*.cmake          whitespace=tab-in-indent,no-lf-at-eof
+
+# ExternalData content links must have LF newlines
+*.md5            crlf=input
+*.sha512         crlf=input
+
+# ghostflow-director GitHub automatic check for maximum repository file size
+#  *                     hooks-max-size=100000