check .git before create pre-commit hook (#276)

CMakeLists.txt

@@ -310,19 +310,24 @@ add_custom_target(
 )
 
 
-# Create the pre-commit hook every time we run cmake
-set(PRE_COMMIT_HOOK ${CMAKE_CURRENT_SOURCE_DIR}/.git/hooks/pre-commit)
-execute_process(
-    COMMAND
-    "rm" "-f" ${PRE_COMMIT_HOOK}
-)
-execute_process(
-    COMMAND
-    "ln" "-s" ${CMAKE_CURRENT_SOURCE_DIR}/cpplint/bin/pre-commit.sh ${PRE_COMMIT_HOOK}
-	RESULT_VARIABLE retcode
-)
-IF(${retcode} EQUAL 0)
-    MESSAGE(STATUS "Creating pre-commit hook done")
+IF(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/.git/")
+    # Create the pre-commit hook every time we run cmake
+    message(STATUS "Create the pre-commit hook")
+    set(PRE_COMMIT_HOOK ${CMAKE_CURRENT_SOURCE_DIR}/.git/hooks/pre-commit)
+    execute_process(
+        COMMAND
+        "rm" "-f" ${PRE_COMMIT_HOOK}
+    )
+    execute_process(
+        COMMAND
+        "ln" "-s" ${CMAKE_CURRENT_SOURCE_DIR}/cpplint/bin/pre-commit.sh ${PRE_COMMIT_HOOK}
+        RESULT_VARIABLE retcode
+    )
+    IF(${retcode} EQUAL 0)
+        MESSAGE(STATUS "Creating pre-commit hook done")
+    ELSE()
+        MESSAGE(FATAL_ERROR "Creating pre-commit hook failed: ${retcode}")
+    ENDIF()
 ELSE()
-    MESSAGE(FATAL_ERROR "Creating pre-commit hook failed: ${retcode}")
+    MESSAGE(FATAL_ERROR "Currently, we don't support downloaded source code.\nPlease using git clone it and rebuild.")
 ENDIF()