bug#10705: 24.0.93; Collect strings matching regexp from Isearch

[Juri Linkov <juri@jurta.org>]

Currently `isearch-occur' is not in sync with the interactive specification
of `occur' that provides a new feature of `C-u M-x occur RET' that collects
the matching strings into the `*Occur*' buffer without line numbers.

The following patch syncs code from `occur-read-primary-args' to `isearch-occur'.

It doesn't quit Isearch when there are no subexpression in the regexp
(it collects the entire match with "\\&").

But in case of subexpression in the regexp, it quits Isearch because
it needs to ask for a substituted replacement string using `read-string'.

=== modified file 'lisp/isearch.el'
--- lisp/isearch.el	2012-01-25 17:54:01 +0000
+++ lisp/isearch.el	2012-02-02 21:01:12 +0000
@@ -1467,12 +1467,27 @@ (defun isearch-occur (regexp &optional n
 Interactively, REGEXP is the current search regexp or a quoted search
 string.  NLINES has the same meaning as in `occur'."
   (interactive
-   (list
-    (cond
-     (isearch-word (word-search-regexp isearch-string))
-     (isearch-regexp isearch-string)
-     (t (regexp-quote isearch-string)))
-    (if current-prefix-arg (prefix-numeric-value current-prefix-arg))))
+   (let* ((perform-collect (consp current-prefix-arg))
+	  (regexp (cond
+		   (isearch-word (word-search-regexp isearch-string))
+		   (isearch-regexp isearch-string)
+		   (t (regexp-quote isearch-string)))))
+     (list regexp
+	   (if perform-collect
+	       ;; Perform collect operation
+	       (if (zerop (regexp-opt-depth regexp))
+		   ;; No subexpression so collect the entire match.
+		   "\\&"
+		 ;; Get the regexp for collection pattern.
+		 (isearch-done nil t)
+		 (isearch-clean-overlays)
+		 (let ((default (car occur-collect-regexp-history)))
+		   (read-string
+		    (format "Regexp to collect (default %s): " default)
+		    nil 'occur-collect-regexp-history default)))
+	     ;; Otherwise normal occur takes numerical prefix argument.
+	     (when current-prefix-arg
+	       (prefix-numeric-value current-prefix-arg))))))
   (let ((case-fold-search isearch-case-fold-search)
 	;; Set `search-upper-case' to nil to not call
 	;; `isearch-no-upper-case-p' in `occur-1'.