Small doc related to new completion functions

* doc/lispref/minibuf.texi (Programmed Completion):
Mention completion-table-with-cache.

* lisp/minibuffer.el (completion-table-dynamic)
(completion-table-with-cache): Doc fixes.

* etc/NEWS: Related markup.  Unrelated copyedit.

2 files changed, 12 insertions, 0 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 6a105a03b3b..6eb45dc3f4f 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2014-02-27  Glenn Morris  <rgm@gnu.org>
+
+        * minibuf.texi (Programmed Completion):
+        Mention completion-table-with-cache.
+
 2014-02-25  Glenn Morris  <rgm@gnu.org>
 
         * display.texi (Window Systems):
diff --git a/doc/lispref/minibuf.texi b/doc/lispref/minibuf.texi
index d618912de8a..fded0dfdd92 100644
--- a/doc/lispref/minibuf.texi
+++ b/doc/lispref/minibuf.texi
@@ -1814,6 +1814,13 @@ possible completions of it.  You can think of
 and the interface for programmed completion functions.
 @end defun
 
+@defun completion-table-with-cache function &optional ignore-case
+This is a wrapper for @code{completion-table-dynamic} that saves the
+last argument-result pair.  This means that multiple lookups with the
+same argument only need to call @var{function} once.  This can be useful
+when a slow operation is involved, such as calling an external process.
+@end defun
+
 @node Completion in Buffers
 @subsection Completion in Ordinary Buffers
 @cindex inline completion