diff --git a/lib/diff.js b/lib/diff.js
index b397ecd2b..c812c9f9b 100644
--- a/lib/diff.js
+++ b/lib/diff.js
@@ -58,6 +58,22 @@ Diff.prototype.findSimilar = function(opts) {
 };
 
 var blobToBuffer = Diff.blobToBuffer;
+/**
+ * Directly run a diff between a blob and a buffer.
+ * @async
+ * @param {Blob} old_blob Blob for old side of diff, or NULL for empty blob
+ * @param {String} old_as_path Treat old blob as if it had this filename;
+ * can be NULL
+ * @param {String} buffer Raw data for new side of diff, or NULL for empty
+ * @param {String} buffer_as_path Treat buffer as if it had this filename;
+ * can be NULL
+ * @param {DiffOptions} opts Options for diff, or NULL for default options
+ * @param {Function} file_cb Callback for "file"; made once if there is a diff;
+ * can be NULL
+ * @param {Function} binary_cb Callback for binary files; can be NULL
+ * @param {Function} hunk_cb Callback for each hunk in diff; can be NULL
+ * @param {Function} line_cb Callback for each line in diff; can be NULL
+ */
 Diff.blobToBuffer= function(
     old_blob,
     old_as_path,