util: Add variant-generator utility

libimagutil/src/lib.rs

@@ -1,3 +1 @@
-#[test]
+pub mod variants;
-fn it_works() {
-}

libimagutil/src/variants.rs

@@ -0,0 +1,23 @@
+/**
+ * Generate variants of a base value by applying parts
+ *
+ * Example:
+ *
+ * ```ignore
+ * generate_variants(path, vec!["foo", "bar", "baz"], |b, v| {
+ *    let b = b.clone();
+ *    b.push(v);
+ *    b
+ * })
+ *
+ * ```
+ *
+ */
+pub fn generate_variants<A, B, C, F>(base: A, modders: Vec<B>, f: &F)
+    -> Vec<C>
+    where
+        F: Fn(&A, B) -> C
+{
+    modders.into_iter().map(|m| f(&base, m)).collect()
+}
+