Adding support for compilation target 'format'

* clang-format 6.0 or above
* TODO: skip files in doc/

.clang-format

@@ -0,0 +1,11 @@
+---
+AccessModifierOffset: '0'
+AlwaysBreakAfterReturnType : All
+AlwaysBreakTemplateDeclarations: 'true'
+BreakBeforeBraces: Linux
+Language: Cpp
+NamespaceIndentation: All
+SpaceBeforeParens: Always
+Standard: Cpp11
+TabWidth: 2
+UseTab: Never

CMakeLists.txt

@@ -93,6 +93,7 @@ endif()
 include("${PCL_SOURCE_DIR}/cmake/pcl_verbosity.cmake")
 include("${PCL_SOURCE_DIR}/cmake/pcl_targets.cmake")
 include("${PCL_SOURCE_DIR}/cmake/pcl_options.cmake")
+include("${PCL_SOURCE_DIR}/cmake/clang-format.cmake")
 
 # Enable verbose timing display?
 if(CMAKE_TIMING_VERBOSE AND UNIX)

cmake/clang-format.cmake

@@ -0,0 +1,22 @@
+file(GLOB_RECURSE
+  ALL_CXX_SOURCE_FILES
+  *.[ch] *.[chi]pp *.[chi]xx *.cppm *.cc *.hh *.ii *.[CHI]
+)
+
+find_program(CLANG_FORMAT 
+  NAMES clang-format-9.0 clang-format-8.0 clang-format-7.0 clang-format-6.0
+  clang-format-9 clang-format-8 clang-format-7 clang-format-6
+)
+
+if(CLANG_FORMAT)
+  add_custom_target(
+    format
+    COMMAND ${CLANG_FORMAT}
+    -i
+    -style=file
+    ${ALL_CXX_SOURCE_FILES}
+  )
+  message(STATUS "Using ${CLANG_FORMAT} for target 'format'")
+else()
+  message(WARNING "No suitable clang-format (>=6.0) found")
+endif()