Re: New function: vc-ediff

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I cleaned up the patch and also updated Changelogs, NEWS and manual.



> +@findex vc-ediff
> +The function @code{vc-ediff} works similar to @code{vc-diff} and
> +provides a way to visually compare two revisions of a file an Ediff
                                                            ^^^
                                                            in?

> +2011-03-22  Christoph Scholtes  <cschol2112@googlemail.com>
> +
> +	* vc/ediff-vers.el (ediff-revision-internal): New
> +	function. Factored out interface to ediff-revision without user
> +	interaction.
> +
> +	* vc/ediff.el: Require ediff-vers (for ediff-revision-internal).
> +	(ediff-revision): Use new function ediff-revision-internal.
> +
> +	* vc/vc.el (vc-ediff): New function. Provides functionality
> +	similar to vc-diff using ediff backend.

No need to give any detail about a new function's purpose, just "New
function" is enough: the source code should explain the purpose (either
self-evidently or via comments&docstrings).
Also, remove the empty lines to make it clear that those three file-changes
go together.

> +(defun ediff-revision-internal (rev1 rev2 &optional startup-hook)
> +  ;; Call backend-specific ediff function. Uses `vc.el' or `rcs.el'
> +  ;; depending on `ediff-version-control-package'."
> +  (funcall
> +   (intern (format "ediff-%S-internal" ediff-version-control-package))
> +   rev1 rev2 startup-hook))

I think this is not needed.

> === modified file 'lisp/vc/ediff.el'
> --- lisp/vc/ediff.el	2011-01-25 04:08:28 +0000
> +++ lisp/vc/ediff.el	2011-03-22 03:08:42 +0000
> @@ -120,7 +120,8 @@
>  (eval-when-compile
>    (require 'dired)
>    (require 'ediff-util)
> -  (require 'ediff-ptch))
> +  (require 'ediff-ptch)
> +  (require 'ediff-vers))
>  ;; end pacifier
 
>  (require 'ediff-init)
> @@ -1435,10 +1436,7 @@
>  	   (format "Revision 2 to compare (default %s's current state): "
>  		   (file-name-nondirectory file))))
>      (ediff-load-version-control)
> -    (funcall
> -     (intern (format "ediff-%S-internal" ediff-version-control-package))
> -     rev1 rev2 startup-hooks)
> -    ))
> +    (ediff-revision-internal rev1 rev2 startup-hooks)))
 
If we don't need ediff-revision-internal then I think the above changes
can also be dropped.

> +(defun vc-ediff (historic &optional not-urgent)
> +  "Display diffs between revisions of a file using ediff.
> +Normally this compares the currently selected file with its
> +working revision. With the prefix argument HISTORIC, it reads two revision
> +designators specifying which revisions to compare.
> +
> +The optional argument NOT-URGENT non-nil means it is ok to say no
> +to saving the buffer."
> +  (interactive (list current-prefix-arg t))
> +  (when buffer-file-name (vc-buffer-sync not-urgent))
> +  (let* ((vc-fileset (vc-deduce-fileset not-urgent))
> +         (files (cadr vc-fileset))
> +         (first (car files)))
> +    (cond
> +     ;; FIXME: Only supports one selected file (for now?).
> +     ;; Alternatively, we could spin off a separate ediff session
> +     ;; for each of the selected files.
> +     ((= (length files) 1)
> +      (if historic
> +          ;; Let user select revisions to compare.
> +          (ediff-revision first)

Problem with this code is that you depend on ediff-revision to get
the revision arguments.  E.g. this doesn't provide completion.
IOW we should use more of vc-diff's code here.

> +        (find-file first)
> +        ;; With empty arguments, function compares latest version of
> +        ;; current buffer's file with current buffer.
> +        (ediff-revision-internal "" "")))

Call ediff-vc-internal here.


        Stefan