feat: add a common file saver utility fn

npm/ng-packs/packages/schematics/src/utils/file.ts

@@ -0,0 +1,8 @@
+import { Tree } from '@angular-devkit/schematics';
+
+export function createFileSaver(tree: Tree) {
+  return (filePath: string, fileContent: string) =>
+    tree.exists(filePath)
+      ? tree.overwrite(filePath, fileContent)
+      : tree.create(filePath, fileContent);
+}

npm/ng-packs/packages/schematics/src/utils/index.ts

@@ -3,6 +3,7 @@ export * from './api';
 export * from './ast';
 export * from './common';
 export * from './enum';
+export * from './file';
 export * from './import';
 export * from './model';
 export * from './namespace';