[gen_ast_dump_json_test.py] Skip manual tests when using --update

See https://reviews.llvm.org/D70119

clang/test/AST/gen_ast_dump_json_test.py

@@ -68,6 +68,8 @@ def main():
     update_or_generate_group.add_argument("--update", help="Update the file in-place", action="store_true")
     update_or_generate_group.add_argument("--opts", help="other options",
                                           action="store", default='', type=str)
+    parser.add_argument("--update-manual", help="When using --update, also update files that do not have the "
+                                                "autogenerated disclaimer", action="store_true")
     args = parser.parse_args()
 
     if not args.source:
@@ -89,17 +91,20 @@ def main():
         # When updating the first line of the test must be a RUN: line
         with open(args.source, "r") as srcf:
             first_line = srcf.readline()
-            filters_line_next = False
+            found_autogenerated_line = False
             filters_line = None
             for i, line in enumerate(srcf.readlines()):
-                if filters_line_next:
+                if found_autogenerated_line:
                     # print("Filters line: '", line.rstrip(), "'", sep="")
                     if line.startswith(filters_line_prefix):
                         filters_line = line[len(filters_line_prefix):].rstrip()
                     break
                 if line.startswith(note_firstline):
-                    filters_line_next = True
+                    found_autogenerated_line = True
                     # print("Found autogenerated disclaimer at line", i + 1)
+        if not found_autogenerated_line and not args.update_manual:
+            print("Not updating", args.source, "since it is not autogenerated.")
+            sys.exit(0)
         if not args.filters and filters_line:
             args.filters = filters_line
             print("Inferred filters as '" + args.filters + "'")