Adding support for compilation target 'format'

* clang-format 6.0 or above
* skip files in doc/
* search all possible clang-format names
* might work in cmake 3.5
* added support for windows style paths

.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 +1,50 @@
+# select all files with correct c++ extensions
+file(GLOB_RECURSE
+  ALL_CXX_SOURCE_FILES
+  *.[ch] *.[chi]pp *.[chi]xx *.cppm *.cc *.hh *.ii *.[CHI]
+)
+
+# exclude the docs **for now**
+set(EXCLUDE_REGEX ".*doc[\\|/].*")
+if(${CMAKE_VERSION} VERSION_LESS "3.6.0")
+  foreach(PROPOSED_FILE ${ALL_CXX_SOURCE_FILES})
+    string(REGEX MATCH ${EXCLUDE_REGEX} regex_found ${PROPOSED_FILE})
+    if(regex_found)
+      list(REMOVE_ITEM ${ALL_CXX_SOURCE_FILES} ${PROPOSED_FILE})
+    endif()
+  endforeach()
+else()
+  list(FILTER ALL_CXX_SOURCE_FILES EXCLUDE REGEX ${EXCLUDE_REGEX})
+endif()
+
+find_program(CLANG_FORMAT 
+  NAMES clang-format
+    # backup names
+    clang-format-9.0 clang-format-8.0 clang-format-7.0 clang-format-6.0
+    clang-format-9 clang-format-8 clang-format-7 clang-format-6
+)
+
+# search for version number in clang-format without version number
+if(CLANG_FORMAT)
+  execute_process(
+    COMMAND sh "-c"
+      "${CLANG_FORMAT} --version | grep -oE '[0-9]' | head -n 1" 
+    OUTPUT_VARIABLE CLANG_FORMAT_VERSION
+  )
+  if(${CLANG_FORMAT_VERSION} GREATER_EQUAL 6)
+    set(CLANG_FORMAT_CORRECT ${CLANG_FORMAT})
+  endif()
+endif()
+
+if(CLANG_FORMAT_CORRECT)
+  message(STATUS "Using ${CLANG_FORMAT_CORRECT} for target 'format'")
+  add_custom_target(
+    format
+    COMMAND ${CLANG_FORMAT_CORRECT}
+    -i
+    -style=file
+    ${ALL_CXX_SOURCE_FILES}
+  )
+else()
+  message(WARNING "No suitable clang-format (version >= 6.0) found")
+endif()