Re: [External] : Re: Adding refactoring capabilities to Emacs

[Alfred M. Szmidt]

   Is this whole discussion, or even much of it, really about whether
   to keep diff-mode buffers read-only by default, and whether to
   provide refactoring commands/keys that let you change the content
   in special ways when the buffer is read-only?

You need to define what a "diff buffer" is first.  Is it a file you
open, is it the output from M-x diff-buffer-with-file, is it the
output from C-x v = ?

   I don't really see a fundamental difference between a diff buffer
   and, say, a grep or an occur buffer.  (But yes, you often _apply_
   the diff content, so you want to ensure it keeps to a proper
   formatting.)

Occur and grep buffers are by default read-only (and there is a
regression in that too -- you can no longer edit a grep/occur buffer
easily due to strange font lock or other properties).

They are also not files, if you open a file (any file really) you will
expect to be able to edit it using normal commands not specific to the
mode (i.e. self-inser-command ...).  vc-diff etc, are more akin to
occur and grep -- the user doesn't work against the file, but rather a
buffer.

   We already have, and are used to, the universal idiom of `C-x C-q'
   to toggle a buffer read-only.  I use that in grep and occur buffers
   without a second thought.  Why isn't that "sufficient" for diff
   buffers as well?

Because we are also talking about files on disk.  If you save a
compilation buffer (essentially the same thing as M-x grep or M-x
occur) to disk, and re-open it, it will not be read-only -- and it
would make little sense for it to be so.  Where as M-x compile _will_
be read-only.

   I can see that some might want commands/keys that act on the buffer
   content, including to change it in
   structured/"legitimate"/refactoring ways, while keeping it
   read-only.

One can have both, diff-mode already allows you to edit the file, and
act on it in a structure manner -- much like any programming mode.

   That way, by default, diff buffers would still be read-only by
   default, quitable with `q', but also modifiable in all the usual
   ways after `C-x C-q'.

But diff buffers aren't read-only -- it depends on their context.