Improve 'isearch-delete-char' documentation (Bug#32990)

* doc/emacs/search.texi (Basic Isearch): Index
'isearch-delete-char', its keybinding and the isearch "input
item" concept, and define the latter.
(Error in Isearch): Clarify the different uses of DEL and
C-M-w during isearch.

* lisp/isearch.el (isearch-delete-char): Correct its
documentation and link to the Info node '(emacs)Basic Isearch'
which explains less technically how this function works in
everyday usage.

1 files changed, 8 insertions, 5 deletions

diff --git a/lisp/isearch.el b/lisp/isearch.el
index 31571e11cd5..b180e63d8e8 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -1956,11 +1956,14 @@ and reads its face argument using `hi-lock-read-face-name'."
 
 
 (defun isearch-delete-char ()
-  "Discard last input item and move point back.
-Last input means the last character or the last isearch command
-that added or deleted characters from the search string,
-moved point, toggled regexp mode or case-sensitivity, etc.
-If no previous match was done, just beep."
+  "Undo last input item during a search.
+
+An input item is the result of a command that pushes a new state
+of isearch (as recorded by the `isearch--state' structure) to
+`isearch-cmds'.  Info node `(emacs)Basic Isearch' explains when
+Emacs records a new input item.
+
+If no input items have been entered yet, just beep."
   (interactive)
   (if (null (cdr isearch-cmds))
       (ding)