+/*
+ * Call fn for each reference in the specified submodule for which the
+ * refname begins with base. If trim is non-zero, then trim that many
+ * characters off the beginning of each refname before passing the
+ * refname to fn. flags can be DO_FOR_EACH_INCLUDE_BROKEN to include
+ * broken references in the iteration. If fn ever returns a non-zero
+ * value, stop the iteration and return that value; otherwise, return
+ * 0.
+ */