Save current file with a slightly different name

Question

My files have long filenames and a part of the filename is a date and a version number. Often I'd like to save the file in the buffer using nearly the same name, just change version number or date.

This would be much easier, if I had a command which puts the filename of the current buffer into the kill ring, so that I can open a file, then type C-x C-w (write file), yank the current name with C-y, change it and save it.

I'm using Emacs 24.3 on Windows and 24.4 on Linux. I have to use different filenames and not git for various reasons. I'd be happy if this command worked with AUCTeX / LaTeX as major mode.

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Edit 1:

I made a mistake: I don't want to type C-x C-f (=find file), but C-x C-w (=write file). I corrected this above.

Edit 2:

Found a duplicate question and answer: https://unix.stackexchange.com/a/45381 But there is no better anwswer!

Edit 3:

Here: http://www.gnu.org/software/emacs/manual/html_node/elisp/File-Name-Components.html is a function, which selects the "nondirectory" part of the filname:

Function: file-name-nondirectory filename

This function returns the nondirectory part of filename.

          (file-name-nondirectory "lewis/foo")
               ⇒ "foo"
          (file-name-nondirectory "foo")
               ⇒ "foo"
          (file-name-nondirectory "lewis/")
               ⇒ ""

If I only knew lisp...

Answer 1

There's no need to do all that.

Simply:

1. Still in the original file, hit C-x C-w. You will be prompted for a new filename.
2. Hit M-n, and the current filename will be inserted for you.
3. Edit what you want and hit RET to save the file to this new name.

You will still have the original file. If you want to go back to it, just visit it again with C-x C-f.

Answer 2

Copying the name of file in the current buffer

Here is a function I use from Cameron Desautels' blog that copies the current buffer file name and displays it in minibuffer.

 
;; Source: http://camdez.com/blog/2013/11/14/emacs-show-buffer-file-name/
(defun show-copy-buffer-file-name ()
  "Show the full path to the current file in the minibuffer and also copy it to the kill-ring."
  (interactive)
  (let ((file-name (buffer-file-name)))
    (if file-name
        (progn
          (message file-name)
          (kill-new file-name))
      (error "Buffer not visiting a file"))))

Renaming the name of file in current buffer

Magnar Sveen has implemented the below function in one of his blogs that conveniently renames the current buffer in one go. This is not what you asked for but I thought it could be related to your use case.

;; Source: http://www.whattheemacsd.com/
(defun rename-current-buffer-file ()
  "Renames current buffer and file it is visiting."
  (interactive)
  (let ((name (buffer-name))
        (filename (buffer-file-name)))
    (if (not (and filename (file-exists-p filename)))
        (error "Buffer '%s' is not visiting a file!" name)
      (let ((new-name (read-file-name "New name: " filename)))
        (if (get-buffer new-name)
            (error "A buffer named '%s' already exists!" new-name)
          (rename-file filename new-name 1)
          (rename-buffer new-name)
          (set-visited-file-name new-name)
          (set-buffer-modified-p nil)
          (message "File '%s' successfully renamed to '%s'."
                   name (file-name-nondirectory new-name)))))))