refactor(watch): extract testable maybeBackfillExistingArchives helper

Co-authored-by: Belphemur <197810+Belphemur@users.noreply.github.com>

cmd/cbzoptimizer/commands/watch_command.go

@@ -115,9 +115,7 @@ func WatchCommand(_ *cobra.Command, args []string) error {
 	if err := addRecursiveWatch(watcher, path); err != nil {
 		return fmt.Errorf("failed to watch path %s: %w", path, err)
 	}
-	if backfill {
-		backfillExistingArchives(path, debouncer.Trigger)
-	}
+	maybeBackfillExistingArchives(backfill, path, debouncer.Trigger)
 
 	for {
 		select {
@@ -208,6 +206,17 @@ func backfillExistingArchives(rootPath string, process func(path string)) {
 	}
 }
 
+// maybeBackfillExistingArchives runs backfillExistingArchives against
+// rootPath only when enabled is true. It exists as its own function (rather
+// than inlining the `if` check at the call site) so the gating decision used
+// by WatchCommand can be exercised directly in tests.
+func maybeBackfillExistingArchives(enabled bool, rootPath string, process func(path string)) {
+	if !enabled {
+		return
+	}
+	backfillExistingArchives(rootPath, process)
+}
+
 func shouldProcessWatchEvent(event fsnotify.Event) bool {
 	return event.Has(fsnotify.Create) || event.Has(fsnotify.Write) || event.Has(fsnotify.Rename)
 }

cmd/cbzoptimizer/commands/watch_command_test.go

@@ -181,11 +181,11 @@ func TestWatchCommandBackfillFlagDefaultsToFalse(t *testing.T) {
 	assert.Equal(t, "bool", flag.Value.Type())
 }
 
-func TestBackfillExistingArchivesOnlyInvokedWhenRequested(t *testing.T) {
+func TestMaybeBackfillExistingArchivesOnlyInvokedWhenRequested(t *testing.T) {
 	root := t.TempDir()
 	require.NoError(t, os.WriteFile(filepath.Join(root, "chapter1.cbz"), []byte("data"), 0o644))
 
-	runBackfill := func(backfill bool) []string {
+	runBackfill := func(enabled bool) []string {
 		var found []string
 		var mu sync.Mutex
 		process := func(path string) {
@@ -193,11 +193,9 @@ func TestBackfillExistingArchivesOnlyInvokedWhenRequested(t *testing.T) {
 			defer mu.Unlock()
 			found = append(found, path)
 		}
-		// Mirrors the gating logic in WatchCommand: backfillExistingArchives
-		// must only run when the --backfill flag is set.
-		if backfill {
-			backfillExistingArchives(root, process)
-		}
+		// This is the exact same gating call WatchCommand makes based on the
+		// --backfill flag value.
+		maybeBackfillExistingArchives(enabled, root, process)
 		return found
 	}