cmake: break out the ugly split sources fn

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6bfcdd3..10d1280 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,6 +32,7 @@
 INCLUDE(AddCFlagIfSupported)
 INCLUDE(FindPkgConfig)
 INCLUDE(FindStatNsec)
+INCLUDE(IdeSplitSources)
 
 # Build options
 #

cmake/Modules/IdeSplitSources.cmake

diff --git a/cmake/Modules/IdeSplitSources.cmake b/cmake/Modules/IdeSplitSources.cmake
new file mode 100644
index 0000000..3a4a531
--- /dev/null
+++ b/cmake/Modules/IdeSplitSources.cmake
@@ -0,0 +1,22 @@
+# This function splits the sources files up into their appropriate
+# subdirectories.  This is especially useful for IDEs like Xcode and
+# Visual Studio, so that you can navigate into the git2_tests project,
+# and see the folders within the tests folder (instead of just seeing all
+# source and tests in a single folder.)
+FUNCTION(IDE_SPLIT_SOURCES target)
+	IF(MSVC_IDE OR CMAKE_GENERATOR STREQUAL Xcode)
+		GET_TARGET_PROPERTY(sources ${target} SOURCES)
+		FOREACH(source ${sources})
+			IF(source MATCHES ".*/")
+				STRING(REPLACE ${CMAKE_CURRENT_SOURCE_DIR}/ "" rel ${source})
+				IF(rel)
+					STRING(REGEX REPLACE "/([^/]*)$" "" rel ${rel})
+					IF(rel)
+						STRING(REPLACE "/" "\\\\" rel ${rel})
+						SOURCE_GROUP(${rel} FILES ${source})
+					ENDIF()
+				ENDIF()
+			ENDIF()
+		ENDFOREACH()
+	ENDIF()
+ENDFUNCTION()