Introduce a 'noexport' variable, from es(1).

Some variables are never exported to the environment, most of which are related
to the internal functioning of rc(1). This list was previously harcoded,
however later shells in the rc family (es, xs) included a 'noexport' variable,
which contained the name of variables which should never be exported to the
environment. This commit ports this 'noexport' feature to rc.

hash.c

@@ -229,11 +229,6 @@ extern void initenv(char **envp) {
 		}
 }
 
-static char *neverexport[] = {
-	"apid", "apids", "bqstatus", "cdpath", "home",
-	"ifs", "path", "pid", "ppid", "status", "*"
-};
-
 /* for a few variables that have default values, we export them only
 if they've been explicitly set; maybeexport[n].flag is TRUE if this
 has occurred. */
@@ -255,12 +250,13 @@ void set_exportable(char *s, bool b) {
 
 static bool var_exportable(char *s) {
 	int i;
-	for (i = 0; i < arraysize(neverexport); i++)
-		if (streq(s, neverexport[i]))
-			return FALSE;
+	List *noex;
 	for (i = 0; i < arraysize(maybeexport); i++)
 		if (maybeexport[i].flag == FALSE && streq(s, maybeexport[i].name))
 			return FALSE;
+	for (noex = varlookup("noexport"); noex != NULL; noex = noex->n)
+		if (streq(s, noex->w))
+			return FALSE;
 	return TRUE;
 }
 

main.c

@@ -101,6 +101,9 @@ extern int main(int argc, char *argv[], char *envp[]) {
 		VERSION,
 		"$Release: @(#)" PACKAGE " " VERSION " " DESCRIPTION " $",
 		(void *)0 );
+	assigndefault("noexport",
+		"noexport", "apid", "apids", "bqstatus", "cdpath", "home",
+		"ifs", "path", "pid", "ppid", "status", "*", (void *)0);
 	initenv(envp);
 	initinput();
 	null[0] = NULL;