I use GNU Emacs as my text editor, and I love it. I regularly use it to work with multiple workspaces that have identical sets of files and directories.

After I’ve worked in one workspace for a while, I often want to switch to another workspace. Specifically, I want to close all of the files I have open in the old workspace, then open the corresponding files in the new workspace.

For example, I might press C-x C-b to get a *Buffer List* and see that I have these files open:

 MR Buffer            Size  Mode  File
 -- ------            ----  ----  ----
    foo.cc           10423  C++   ~/src/foo/foo.cc
    foo.h             2933  C++   ~/src/foo/foo.h
.   foo_unittest.cc  17965  C++   ~/src/foo/foo_unittest.cc
    *scratch*            0  Lisp  /tmp/*scratch*
 *  *Messages*         726  Fundamental  

When I finish the change I’m working on in ~/src/, I might want to start a new change in ~/src2/. To do that, I’d have to close foo.cc, foo.h, and foo_unittest.cc, and reopen them in src2.

This elisp adds a command to buffer-menu-mode, used in *Buffer List*, to do just that. To use it, mark the files you want to reopen with m, then press r to run the Buffer-menu-reopen function. It will ask you for a pattern and a replacement, then reopen the marked files in the new location.

(defun Buffer-menu-reopen (regexp replacement)
  "Reopens marked files in a different place by replacing part of their path."
  (interactive "sReplace: \nsWith: ")
  (goto-char (point-min))
  (while (search-forward "\n>" nil t)
    (let* ((original-buffer (Buffer-menu-buffer nil))
           (original-file (buffer-file-name original-buffer)))
      (when (and original-buffer
                 original-file
                 (string-match regexp original-file))
        (let ((new-file (replace-match replacement nil nil original-file)))
          (when (file-exists-p new-file)
            (kill-buffer original-buffer)
            (find-file-noselect new-file))))))
  (list-buffers))

; add keybinding
(define-key Buffer-menu-mode-map "r" 'Buffer-menu-reopen)

; add to docstring
(progn
  (put 'Buffer-menu-mode 'function-documentation nil)
  (put 'Buffer-menu-mode 'function-documentation
       (concat (documentation 'Buffer-menu-mode t)
               "\n\\[Buffer-menu-reopen] -- reopen the files marked with m "
               "in a new place in the filesystem.")))

Similarly, this function reopens the current buffer in a new location.

(defun replace-path-and-reopen (regexp replacement)
  "Reopens the file visited by the current buffer in a different location."
  (interactive "sReplace: \nsWith: ")
  (let ((orig-buffer (current-buffer))
        (orig-file (buffer-file-name (current-buffer))))
    (if (string-match regexp orig-file)
        (progn
          (find-file (replace-match replacement nil nil orig-file))
          (kill-buffer orig-buffer))
      (error "No match for %s in %s" regexp orig-file))))