GR-14345: partial support for -I isolation mode

- todo: script dir still in path

Author: cosminbasca

graalpython/com.oracle.graal.python.shell/src/com/oracle/graal/python/shell/GraalPythonMain.java

@@ -63,6 +63,7 @@ public static void main(String[] args) {
     private ArrayList<String> programArgs = null;
     private String commandString = null;
     private String inputFile = null;
+    private boolean ignoreScriptDir = false;
     private boolean ignoreEnv = false;
     private boolean inspectFlag = false;
     private boolean verboseFlag = false;
@@ -128,6 +129,11 @@ protected List<String> preprocessArguments(List<String> givenArgs, Map<String, S
                 case "-q":
                     quietFlag = true;
                     break;
+                case "-I":
+                    noUserSite = true;
+                    ignoreEnv = true;
+                    ignoreScriptDir = true;
+                    break;
                 case "-s":
                     noUserSite = true;
                     break;
@@ -557,6 +563,7 @@ protected void printHelp(OptionCategory maxCategory) {
                         // "-Q arg : division options: -Qold (default), -Qwarn, -Qwarnall, -Qnew\n"
                         // +
                         "-q     : don't print version and copyright messages on interactive startup\n" +
+                        "-I     : don't add user site and script directory to sys.path; also PYTHONNOUSERSITE\n" +
                         "-s     : don't add user site directory to sys.path; also PYTHONNOUSERSITE\n" +
                         "-S     : don't imply 'import site' on initialization\n" +
                         // "-t : issue warnings about inconsistent tab usage (-tt: issue errors)\n"