migrate: don't allow migrating more than once and if not migrated at boot

Author: IAmTheNerdNextDoor

apps/migrate.c

@@ -140,6 +140,17 @@ int main(int argc, char * argv[]) {
 
 	hashmap_t * cmdline = get_cmdline();
 
+	if (fopen("/.migrated", "r")) {
+	    printf("You have already migrated the filesystem.\n");
+		return 1;
+	}
+
+	if (!hashmap_has(cmdline, "migrate")) {
+	    printf("Assuming you are trying to run migrate after the system has booted without migrating, this will break things!\n");
+		printf("Please reboot the system with migrate in the cmdline.\n");
+		return 1;
+	}
+
 	if (hashmap_has(cmdline, "logtoserial")) {
 		_debug = 1;
 	}
@@ -191,5 +202,7 @@ int main(int argc, char * argv[]) {
 		free(tmp);
 	}
 
+	system("touch /.migrated");
+
 	return 0;
 }