refactor(cogify): restructure background colour support code

packages/cogify/src/cogify/cli/cli.cog.ts

@@ -331,28 +331,28 @@ async function createCog(ctx: CogCreationContext): Promise<URL> {
   );
   await new GdalRunner(vrtWarpCommand).run(logger);
 
-  if (options.background) {
-    // Create a tiff with background to fill the empty space in the target cog
-    const gdalCreateCommand = gdalCreate(new URL(`${tileId}-bg.tiff`, ctx.tempFolder), options);
-    await new GdalRunner(gdalCreateCommand).run(logger);
-
-    // Create a vrt layering with the backgroud tiff
-    const vrtMergeCommand = gdalBuildVrt(new URL(`${tileId}-merged.vrt`, ctx.tempFolder), [
-      gdalCreateCommand.output,
-      vrtWarpCommand.output,
-    ]);
-    await new GdalRunner(vrtMergeCommand).run(logger);
-
-    // Create the COG from the merged Vrt with background
-    const cogCreateCommand = gdalBuildCog(new URL(`${tileId}.tiff`, ctx.tempFolder), vrtMergeCommand.output, options);
-    await new GdalRunner(cogCreateCommand).run(logger);
-    return cogCreateCommand.output;
-  } else {
+  if (options.background == null) {
     // Create the COG from the warped vrt without background
     const cogCreateCommand = gdalBuildCog(new URL(`${tileId}.tiff`, ctx.tempFolder), vrtWarpCommand.output, options);
     await new GdalRunner(cogCreateCommand).run(logger);
     return cogCreateCommand.output;
   }
+
+  // Create a tiff with background to fill the empty space in the target cog
+  const gdalCreateCommand = gdalCreate(new URL(`${tileId}-bg.tiff`, ctx.tempFolder), options);
+  await new GdalRunner(gdalCreateCommand).run(logger);
+
+  // Create a vrt layering with the background tiff
+  const vrtMergeCommand = gdalBuildVrt(new URL(`${tileId}-merged.vrt`, ctx.tempFolder), [
+    gdalCreateCommand.output,
+    vrtWarpCommand.output,
+  ]);
+  await new GdalRunner(vrtMergeCommand).run(logger);
+
+  // Create the COG from the merged Vrt with background
+  const cogCreateCommand = gdalBuildCog(new URL(`${tileId}.tiff`, ctx.tempFolder), vrtMergeCommand.output, options);
+  await new GdalRunner(cogCreateCommand).run(logger);
+  return cogCreateCommand.output;
 }
 
 /**