diff --git a/refs.c b/refs.c
index 597800a5ed..af34c3b5ec 100644
--- a/refs.c
+++ b/refs.c
@@ -21,6 +21,11 @@ struct ref_array {
 	struct ref_entry **refs;
 };
 
+/*
+ * Parse one line from a packed-refs file.  Write the SHA1 to sha1.
+ * Return a pointer to the refname within the line (null-terminated),
+ * or NULL if there was a problem.
+ */
 static const char *parse_ref_line(char *line, unsigned char *sha1)
 {
 	/*