isearch-search-fun-function doc tweak

* lisp/isearch.el (isearch-search-fun-function): Mention what
the STRING parameter is (bug#21552).

(cherry picked from commit cafc2a5940cdc523cfea6dcf1cf540f48367c62a)

diff --git a/lisp/isearch.el b/lisp/isearch.el
index 218c18a666e6d3cd995b8649c3f89a6e9f9233fe..b2223e7b3081c2cf874d64be96fc39adae6d0b66 100644 (file)
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -2662,8 +2662,9 @@ the word mode."
   "Non-default value overrides the behavior of `isearch-search-fun-default'.
 This variable's value should be a function, which will be called
 with no arguments, and should return a function that takes three
-arguments: STRING, BOUND, and NOERROR.  See `re-search-forward'
-for the meaning of BOUND and NOERROR arguments.
+arguments: STRING, BOUND, and NOERROR.  STRING is the string to
+be searched for.  See `re-search-forward' for the meaning of
+BOUND and NOERROR arguments.
 
 This returned function will be used by `isearch-search-string' to
 search for the first occurrence of STRING.")