add clang-format

src/.clang-format

+---
+BasedOnStyle: LLVM
+AccessModifierOffset: '-4'
+AlignConsecutiveAssignments: 'false'
+AlignConsecutiveDeclarations: 'false'
+AlignEscapedNewlines: DontAlign
+AlignOperands: 'true'
+AlignTrailingComments: 'true'
+AllowShortBlocksOnASingleLine: 'false'
+AllowShortCaseLabelsOnASingleLine: 'false'
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: 'false'
+AllowShortLoopsOnASingleLine: 'false'
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: 'true'
+AlwaysBreakTemplateDeclarations: 'true'
+BreakBeforeBraces: Attach
+BreakConstructorInitializers: BeforeColon
+ColumnLimit: '100'
+Cpp11BracedListStyle: 'true'
+FixNamespaceComments: 'false'
+IndentCaseLabels: 'false'
+IndentWidth: '4'
+IndentWrappedFunctionNames: 'true'
+KeepEmptyLinesAtTheStartOfBlocks: 'false'
+Language: Cpp
+MaxEmptyLinesToKeep: '1'
+NamespaceIndentation: None
+PointerAlignment: Right
+ReflowComments: 'true'
+SortIncludes: 'true'
+SortUsingDeclarations: 'true'
+SpaceAfterTemplateKeyword: 'false'
+SpaceBeforeAssignmentOperators: 'true'
+SpaceBeforeParens: Never
+SpaceInEmptyParentheses: 'false'
+SpacesInAngles: 'false'
+SpacesInCStyleCastParentheses: 'false'
+SpacesInContainerLiterals: 'false'
+SpacesInParentheses: 'false'
+SpacesInSquareBrackets: 'false'
+Standard: Cpp11
+TabWidth: '4'
+UseTab: ForIndentation
+
+...