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

[Juri Linkov]

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'.