Ask for account password if -password is omitted from command line.

DepotDownloader/Program.cs

@@ -120,6 +120,13 @@ namespace DepotDownloader
             bool bNoExclude = HasParameter( args, "-no-exclude" );
             bool bAllPlatforms = HasParameter( args, "-all-platforms" );
 
+            if (username != null && password == null)
+            {
+                Console.Write( "Enter account password: " );
+                password = Util.ReadPassword();
+                Console.WriteLine();
+            }
+
             if ( !bGameserver && !bApp )
             {
                 ContentDownloader.Download( depotId, depotVersion, cellId, username, password, !bDebot, false, false, installDir, files );

DepotDownloader/Util.cs

@@ -64,5 +64,30 @@ namespace DepotDownloader
 
             return bytes;
         }
+
+        public static string ReadPassword()
+        {
+            ConsoleKeyInfo keyInfo;
+            StringBuilder password = new StringBuilder();
+
+            do 
+            {
+                keyInfo = Console.ReadKey( true );
+
+                if ( keyInfo.Key == ConsoleKey.Backspace )
+                {
+                    if ( password.Length > 0 )
+                        password.Remove( password.Length - 1, 1 );
+                    continue;
+                }
+
+                /* Printable ASCII characters only */
+                char c = keyInfo.KeyChar;
+                if ( c >= ' ' && c <= '~' )
+                    password.Append( c );
+            } while ( keyInfo.Key != ConsoleKey.Enter );
+
+            return password.ToString();
+        }
     }
 }