Add option to specify extra arguments for cmake-format (#37)

The arguments are documented here: https://github.com/cheshirekow/cmake_format#usage

CMakeLists.txt

@@ -51,8 +51,8 @@ if(GIT_PROGRAM AND CMAKE_FORMAT_PROGRAM)
       ${name}
       COMMAND
         ${CMAKE_COMMAND} -DGIT_PROGRAM=${GIT_PROGRAM} -DCMAKE_FORMAT_PROGRAM=${CMAKE_FORMAT_PROGRAM}
-        -DCMAKE_FORMAT_TARGET=${name} -DBINARY_DIR=${CMAKE_CURRENT_BINARY_DIR}
-        -DCMAKE_FORMAT_EXCLUDE=${CMAKE_FORMAT_EXCLUDE} -P
+        -DCMAKE_FORMAT_EXTRA_ARGS=${CMAKE_FORMAT_EXTRA_ARGS} -DCMAKE_FORMAT_TARGET=${name}
+        -DBINARY_DIR=${CMAKE_CURRENT_BINARY_DIR} -DCMAKE_FORMAT_EXCLUDE=${CMAKE_FORMAT_EXCLUDE} -P
         ${CMAKE_CURRENT_LIST_DIR}/cmake-format.cmake
       VERBATIM
       WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}

README.md

@@ -19,6 +19,10 @@ To disable using _cmake_format_ to format CMake files, set the cmake option `FOR
 
 To disable using _clang_format_ to format clang-supported files, set the cmake option `FORMAT_SKIP_CLANG` to a truthy value, e.g. by invoking CMake with `-DFORMAT_SKIP_CLANG=YES`, or enabling the option when [adding the dependency](#how-to-integrate) (recommended).
 
+To specify a extra arguments for cmake-format, use the cmake option `CMAKE_FORMAT_EXTRA_ARGS`, e.g. by invoking CMake with `-DCMAKE_FORMAT_EXTRA_ARGS="-c /path/to/cmake-format-config.{yaml,json,py}"`,
+or by enabling the option when [adding the dependency](#how-to-integrate) (recommended).
+
+
 ## Demo
 
 ![](https://user-images.githubusercontent.com/4437447/66123312-31ec3500-e5d1-11e9-8404-492b8eff8511.gif)
@@ -52,6 +56,8 @@ CPMAddPackage(
       "FORMAT_SKIP_CLANG NO"
       # path to exclude (optional, supports regular expressions)
       "CMAKE_FORMAT_EXCLUDE cmake/CPM.cmake"
+      # extra arguments for cmake_format (optional)
+      "CMAKE_FORMAT_EXTRA_ARGS -c /path/to/cmake-format.{yaml,json,py}"
 )
 ```
 

cmake-format.cmake

@@ -37,8 +37,10 @@ get_cmake_files(
   "\\.cmake$|(^|/)CMakeLists\\.txt$"
 )
 
+separate_arguments(CMAKE_FORMAT_EXTRA_ARGS)
+
 if(CMAKE_FORMAT_TARGET STREQUAL fix-cmake-format)
-  execute_process(COMMAND ${CMAKE_FORMAT_PROGRAM} -i ${CMAKE_FILES})
+  execute_process(COMMAND ${CMAKE_FORMAT_PROGRAM} ${CMAKE_FORMAT_EXTRA_ARGS} -i ${CMAKE_FILES})
   return()
 endif()
 
@@ -49,7 +51,11 @@ endif()
 set(formatted_cmake_file ${BINARY_DIR}/formatted.cmake)
 foreach(cmake_file IN LISTS CMAKE_FILES)
   set(source_cmake_file ${CMAKE_SOURCE_DIR}/${cmake_file})
-  execute_process(COMMAND ${CMAKE_FORMAT_PROGRAM} -o ${formatted_cmake_file} ${source_cmake_file})
+  execute_process(
+    COMMAND ${CMAKE_FORMAT_PROGRAM} ${CMAKE_FORMAT_EXTRA_ARGS} -o ${formatted_cmake_file}
+            ${source_cmake_file}
+  )
+
   execute_process(
     COMMAND ${GIT_PROGRAM} diff -G. --color --no-index -- ${source_cmake_file}
             ${formatted_cmake_file} RESULT_VARIABLE result ${OUTPUT_QUIET_OPTION}