Enable cscope to exclude test source files (#4190)

Summary:
Usually when using cscope, the query results contain a lot of function calls in test, making it hard to browse. So this PR aims to provide an option to exclude test source files.

Add a new PHONY target, tags0, to exclude test source files while using cscope.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4190

Differential Revision: D9015901

Pulled By: riversand963

fbshipit-source-id: ea9a45756ccff5b26344d37e9ff1c02c5d9736d6

Makefile

@@ -666,7 +666,7 @@ $(SHARED4): $(shared_all_libobjects)
 endif  # PLATFORM_SHARED_EXT
 
 .PHONY: blackbox_crash_test check clean coverage crash_test ldb_tests package \
-	release tags valgrind_check whitebox_crash_test format static_lib shared_lib all \
+	release tags tags0 valgrind_check whitebox_crash_test format static_lib shared_lib all \
 	dbg rocksdbjavastatic rocksdbjava install install-static install-shared uninstall \
 	analyze tools tools_lib
 
@@ -1019,6 +1019,13 @@ tags:
 	cscope -b `$(FIND) . -name '*.cc'` `$(FIND) . -name '*.h'` `$(FIND) . -name '*.c'`
 	ctags -e -R -o etags *
 
+tags0:
+	ctags -R .
+	cscope -b `$(FIND) . -name '*.cc' -and ! -name '*_test.cc'` \
+		  `$(FIND) . -name '*.c' -and ! -name '*_test.c'` \
+		  `$(FIND) . -name '*.h' -and ! -name '*_test.h'`
+	ctags -e -R -o etags *
+
 format:
 	build_tools/format-diff.sh