+/*
+ * Fetch ref (relative to $GIT_DIR/refs) from the remote, and store
+ * the 20-byte SHA1 in sha1. Return 0 on success, -1 on failure. To
+ * be provided by the particular implementation.
+ */
+extern int fetch_ref(char *ref, unsigned char *sha1);
+
+/* If set, the ref filename to write the target value to. */
+extern const char *write_ref;
+
+/* If set, the hash that the current value of write_ref must be. */
+extern const unsigned char *current_ref;
+
+/* Set to fetch the target tree. */