[objcmt] Introduce "objcmt-white-list-dir-path=" option.

This options accepts a path to a directory, collects the filenames of the files
it contains, and the migrator will only modify files with the same filename.

llvm-svn: 194710

clang/lib/Frontend/CompilerInvocation.cpp

@@ -821,6 +821,8 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   if (Args.hasArg(OPT_objcmt_migrate_all))
     Opts.ObjCMTAction |= FrontendOptions::ObjCMT_MigrateDecls;
 
+  Opts.ObjCMTWhiteListPath = Args.getLastArgValue(OPT_objcmt_white_list_dir_path);
+
   if (Opts.ARCMTAction != FrontendOptions::ARCMT_None &&
       Opts.ObjCMTAction != FrontendOptions::ObjCMT_None) {
     Diags.Report(diag::err_drv_argument_not_allowed_with)