July 5, 2011
Move line to end of file and comment
I had to work on a bunch of translation Java property files in an ancient J2EE project that had old translations in between the new ones resulting in a hardly readable mess that confused the hell out of Netbeans’ property file editor plugin, so I decided to just move all those old lines to the bottom of the file and comment them out.
For this I quickly hacked up two elisp functions
(defun move-line-to-end-of-file ()
"Move the current line to the end of the file."
(interactive)
(save-excursion
(beginning-of-line)
(kill-whole-line)
(end-of-buffer)
(yank-as-comment)))
(defun yank-as-comment ()
"Yank the last killed selection as a comment, but leave text
alone that is already a comment according to the current mode."
(interactive)
(save-excursion
(yank)
(if (not (comment-only-p (mark) (point)))
(comment-region (mark) (point)))))
There probably is a much more idiomatic way to do this (which I’d love to hear about), but this seems to work just fine for my use. Note however that move-line-to-end-of-file will just append to the last line if the file doesn’t end with a newline (which isn’t an issue in my case).
theBlackDragon's Blog 
Ian Eure said,
August 23, 2011 at 01:38
The kmacro stuff can probably get you most of the way there, but I think it’s a tossup. You’d need to push the mark or set a register or something to jump back to your source line after running the macro, so it seems a bit more fragile.
If you can add (when (not (looking-at “\\n”)) (insert “\\n”)) to yank-as-comment to work around the lack of newline.
theBlackDragon said,
August 31, 2011 at 16:23
Thanks, that works wonderfully!
One thing I forgot to mention (and that bit me when I needed this function again) is that comment-only-p is defined in newcomment.el so it needs to be loaded.