Doing search and replace via *grep* buffer

[storm@cua.dk (Kim F. Storm)]

Here is a small patch which provides a very handy search and replace
functionality via the normal grep interfaces (including lgrep/rgrep).

It requires that grep regexp highlighting works (I suppose most modern
grep programs do that).


Here is an example of its use, replacing _some_ occurrences of 
the identifier `oldtext' with `newtext':

First use rgrep to search for oldtext in all .c and .h files:
  M-x rgrep RET oldtext RET ch RET RET

Then in the *grep* buffer, move to the first instance which you want to
replace (use `n' or C-n).

Then hit / and type the replacement text:
  / newtext RET

Now, still in the *grep* buffer, move to the next instance you want
to modify, and just hit . to repeat the replacement, for example:
  n n . n . n . n n n .

(I suppose VI users will find this very familiar).


*** grep.el	14 Feb 2007 12:54:20 +0100	1.69
--- grep.el	15 Feb 2007 12:46:01 +0100	
***************
*** 185,192 ****
--- 185,195 ----
      (define-key map "\r" 'compile-goto-error)  ;; ?
      (define-key map "n" 'next-error-no-select)
      (define-key map "p" 'previous-error-no-select)
+     (define-key map "o" 'grep-goto-error-no-select)
      (define-key map "{" 'compilation-previous-file)
      (define-key map "}" 'compilation-next-file)
+     (define-key map "/" 'grep-replace-match)
+     (define-key map "." 'grep-repeat-replace-match)
      (define-key map "\t" 'compilation-next-error)
      (define-key map [backtab] 'compilation-previous-error)
  
***************
*** 790,795 ****
--- 793,831 ----
  	  (if (eq next-error-last-buffer (current-buffer))
  	      (setq default-directory dir)))))))
  
+ (defun grep-goto-error-no-select ()
+   "Display currently grep match in other window."
+   (interactive)
+   (save-selected-window
+     (compile-goto-error)))
+ 
+ (defvar grep-last-replace-string nil)
+ 
+ (defun grep-replace-match-internal ()
+   (when compilation-highlight-overlay
+     (let ((start (overlay-start compilation-highlight-overlay)))
+       (goto-char start)
+       (undo-boundary)
+       (delete-region start (overlay-end compilation-highlight-overlay))
+       (insert grep-last-replace-string)
+       (move-overlay compilation-highlight-overlay start (point)))))
+ 
+ (defun grep-replace-match (string)
+   "Replace current grep match with string STRING."
+   (interactive "sReplace with: ")
+   (save-selected-window
+     (setq grep-last-replace-string string)
+     (let ((next-error-highlight
+ 	   (if (numberp next-error-highlight) next-error-highlight 0.01))
+ 	  (next-error-hook '(grep-replace-match-internal)))
+       (compile-goto-error))))
+ 
+ (defun grep-repeat-replace-match ()
+   "Replace current grep match with last match replace string."
+   (interactive)
+   (if (not grep-last-replace-string)
+       (call-interactively 'grep-replace-match)
+     (grep-replace-match grep-last-replace-string)))
+ 
  
  (provide 'grep)
  

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk