format: add --api-prefix CLI option (envoyproxy#3108)

Needed for checking format when embedded in a parent project.

Signed-off-by: Matt Klein <[email protected]>

tools/check_format.py

@@ -94,7 +94,7 @@ def checkProtobufExternalDeps(file_path):
 
 
 def isApiFile(file_path):
-  return file_path.startswith('./api/')
+  return file_path.startswith(args.api_prefix)
 
 
 def isBuildFile(file_path):
@@ -291,6 +291,7 @@ def checkFormatVisitor(arg, dir_name, names):
   parser.add_argument('--add-excluded-prefixes', type=str, nargs="+", help="exclude additional prefixes.")
   parser.add_argument('-j', '--num-workers', type=int, default=multiprocessing.cpu_count(),
                       help="number of worker processes to use; defaults to one per core.")
+  parser.add_argument('--api-prefix', type=str, default='./api/', help="path of the API tree")
   args = parser.parse_args()
 
   operation_type = args.operation_type