support addprefix()

addprefix(prefix, base) takes a `prefix` and a (possibly space-separated) `base` string,
and append `prefix` to the beginning of each word in the base string;
for example, addprefix('src', 'foo bar baz') -> 'src/foo src/bar src/baz'

src/function.rs

@@ -21,6 +21,7 @@ pub(crate) fn get(name: &str) -> Option<Function> {
   let function = match name {
     "absolute_path" => Unary(absolute_path),
     "arch" => Nullary(arch),
+    "addprefix" => Binary(addprefix),
     "blake3" => Unary(blake3),
     "blake3_file" => Unary(blake3_file),
     "canonicalize" => Unary(canonicalize),
@@ -255,6 +256,16 @@ fn invocation_directory_native(context: &FunctionContext) -> Result<String, Stri
     })
 }
 
+fn addprefix(_context: &FunctionContext, pref: &str, base: &str) -> Result<String, String> {
+  Ok(
+    base
+      .split(" ")
+      .map(|s| format!("{pref}{s}"))
+      .collect::<Vec<String>>()
+      .join(" "),
+  )
+}
+
 fn join(
   _context: &FunctionContext,
   base: &str,

tests/functions.rs

@@ -481,6 +481,20 @@ fn trim_end() {
   assert_eval_eq("trim_end('  f  ')", "  f");
 }
 
+#[test]
+fn addprefix() {
+  assert_eval_eq("addprefix('8', 'r s t')", "8r 8s 8t");
+  assert_eval_eq(
+    "addprefix('src/', 'main sar x11')",
+    "src/main src/sar src/x11",
+  );
+  assert_eval_eq("addprefix('-', 'c v h y')", "-c -v -h -y");
+  assert_eval_eq(
+    "addprefix('0000', '11 10 01 00')",
+    "000011 000010 000001 000000",
+  );
+}
+
 #[test]
 #[cfg(not(windows))]
 fn join() {