Doubling down on the BackupStrategy. Expecting to move this into both 'ac' as well as the GUI.

app/cli-acx/src/main/java/io/github/applecommander/acx/base/ReadWriteDiskCommandOptions.java

@@ -19,6 +19,7 @@
  */
 package io.github.applecommander.acx.base;
 
+import org.applecommander.util.BackupStrategy;
 import picocli.CommandLine.Option;
 
 public abstract class ReadWriteDiskCommandOptions extends ReadOnlyDiskImageCommandOptions {
@@ -33,11 +34,7 @@ public abstract class ReadWriteDiskCommandOptions extends ReadOnlyDiskImageComma
         int returnCode = handleCommand();
         
         if (returnCode == 0) {
-            BackupStrategy backupStrategy = switch (backupCode) {
-                case "" -> BackupStrategy.none();
-                case "bak" -> BackupStrategy.fileExtension("bak");
-                default -> BackupStrategy.directory(backupCode);
-            };
+            BackupStrategy backupStrategy = BackupStrategy.create(backupCode);
             saveDisk(selectedDisks().getFirst(), backupStrategy);
         }
         

app/cli-acx/src/main/java/io/github/applecommander/acx/base/ReusableCommandOptions.java

@@ -20,6 +20,7 @@
 package io.github.applecommander.acx.base;
 
 import com.webcodepro.applecommander.storage.FormattedDisk;
+import org.applecommander.util.BackupStrategy;
 import picocli.CommandLine.Command;
 import picocli.CommandLine.Option;
 

app/cli-acx/src/main/java/io/github/applecommander/acx/command/ConvertCommand.java

@@ -22,7 +22,7 @@ package io.github.applecommander.acx.command;
 import com.webcodepro.applecommander.storage.DiskFactory;
 import com.webcodepro.applecommander.storage.Disks;
 import com.webcodepro.applecommander.storage.FormattedDisk;
-import io.github.applecommander.acx.base.BackupStrategy;
+import org.applecommander.util.BackupStrategy;
 import io.github.applecommander.acx.base.ReusableCommandOptions;
 import org.applecommander.source.Source;
 import org.applecommander.source.Sources;

app/cli-acx/src/main/java/io/github/applecommander/acx/command/CreateDiskCommand.java

@@ -27,7 +27,7 @@ import com.webcodepro.applecommander.storage.os.pascal.PascalFormatDisk;
 import com.webcodepro.applecommander.storage.os.prodos.ProdosFormatDisk;
 import io.github.applecommander.acx.OrderType;
 import io.github.applecommander.acx.SystemType;
-import io.github.applecommander.acx.base.BackupStrategy;
+import org.applecommander.util.BackupStrategy;
 import io.github.applecommander.acx.base.ReusableCommandOptions;
 import io.github.applecommander.acx.converter.DataSizeConverter;
 import org.applecommander.device.*;

lib/ac-api/src/main/java/org/applecommander/util/BackupStrategy.java

@@ -17,7 +17,7 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  */
-package io.github.applecommander.acx.base;
+package org.applecommander.util;
 
 import java.io.IOException;
 import java.nio.file.Files;
@@ -26,13 +26,46 @@ import java.nio.file.Path;
 import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;
 
 /// Provides a simple but automated backup strategy to the `acx` tool.
+///
+/// General usage pattern is as follows:
+/// ```java
+/// // Only save if there are changes.
+/// if (disk.getSource().hasChanged()) {
+///     backupStrategy.backup(disk.getFilename());
+///     disk.save();
+/// }
+/// ```
+///
+/// To create a `BackupStrategy` in a consistent manner, use the #create
+/// method:
+/// ```'java
+/// BackupStrategy backupStrategy = BackupStrategy.create("bak");
+/// ```
+///
+/// If using in a context where a backup is no expected (as in a new file, or
+/// a "save as" situation), simply use `BackupStrategy.none()`.
+///
+/// The coding is as follows:
+/// * `null` or blank (`""`): Returns an ineffective strategy. (No branches in code.)
+/// * `bak`: Returns a backup strategy that renames the existing file from `name.dsk`
+///   to `name.dsk.bak`, overwriting any existing files.
+/// * The default strategy is to assume the value is a directory, _which will be created_,
+///   and make a copy of the file into this directory.
+///
+/// @see #create(String)
 /// @see #none()
-/// @see #fileExtension(String) 
-/// @see #directory(String)
-/// @see ReadWriteDiskCommandOptions
 public interface BackupStrategy {
         void backup(String filename) throws IOException;
 
+        static BackupStrategy create(String backupCode) {
+            if (backupCode == null) backupCode = "";
+            return switch (backupCode) {
+                case "" -> BackupStrategy.none();
+                case "bak" -> BackupStrategy.fileExtension("bak");
+                default -> BackupStrategy.directory(backupCode);
+            };
+        }
+
         static BackupStrategy none() {
             return filename -> {
                 // Do nothing