bug#6870: Make vc-root-diff work in more modes

bug#6870: Make vc-root-diff work in more modes

[rogers-emacs]

   It makes sense to me that vc-root-diff uses "(vc-responsible-backend
default-directory)" when in a dired-mode buffer.  But since vc-root-diff
is not at all about the current buffer, why not also make that the
default for shell-mode, diff-mode, or any of the other modes for
non-version-controlled buffers that may be generated in a working copy?

					-- Bob Rogers
					   http://www.rgrjr.com/

------------------------------------------------------------------------
diff --git a/lisp/vc.el b/lisp/vc.el
index 1e52a3c..abba202 100644
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -1655,8 +1655,8 @@ saving the buffer."
     (when buffer-file-name (vc-buffer-sync not-urgent))
     (let ((backend
 	   (cond ((derived-mode-p 'vc-dir-mode)  vc-dir-backend)
-		 ((derived-mode-p 'dired-mode) (vc-responsible-backend default-directory))
-		 (vc-mode (vc-backend buffer-file-name))))
+		 (vc-mode (vc-backend buffer-file-name))
+		 (t (vc-responsible-backend default-directory))))
 	  rootdir working-revision)
       (unless backend
 	(error "Buffer is not version controlled"))

bug#6870: Make vc-root-diff work in more modes

[Lars Magne Ingebrigtsen]

rogers-emacs@rgrjr.dyndns.org writes:

>    It makes sense to me that vc-root-diff uses "(vc-responsible-backend
> default-directory)" when in a dired-mode buffer.  But since vc-root-diff
> is not at all about the current buffer, why not also make that the
> default for shell-mode, diff-mode, or any of the other modes for
> non-version-controlled buffers that may be generated in a working copy?
>
> 					-- Bob Rogers
> 					   http://www.rgrjr.com/
>
> ------------------------------------------------------------------------
> diff --git a/lisp/vc.el b/lisp/vc.el
> index 1e52a3c..abba202 100644
> --- a/lisp/vc.el
> +++ b/lisp/vc.el
> @@ -1655,8 +1655,8 @@ saving the buffer."
>      (when buffer-file-name (vc-buffer-sync not-urgent))
>      (let ((backend
>  	   (cond ((derived-mode-p 'vc-dir-mode)  vc-dir-backend)
> -		 ((derived-mode-p 'dired-mode) (vc-responsible-backend default-directory))
> -		 (vc-mode (vc-backend buffer-file-name))))
> +		 (vc-mode (vc-backend buffer-file-name))
> +		 (t (vc-responsible-backend default-directory))))
>  	  rootdir working-revision)
>        (unless backend
>  	(error "Buffer is not version controlled"))

This looks very reasonable to me, but I'm not all that familiar with
vc.el internals.  Does anybody else have any opinions on this?

-- 
(domestic pets only, the antidote for overdose, milk.)
  bloggy blog http://lars.ingebrigtsen.no/

bug#6870: Make vc-root-diff work in more modes

[Stefan Monnier]

>> (cond ((derived-mode-p 'vc-dir-mode)  vc-dir-backend)
>> -		 ((derived-mode-p 'dired-mode) (vc-responsible-backend default-directory))
>> -		 (vc-mode (vc-backend buffer-file-name))))
>> +		 (vc-mode (vc-backend buffer-file-name))
>> +		 (t (vc-responsible-backend default-directory))))
>> rootdir working-revision)
>> (unless backend
>> (error "Buffer is not version controlled"))

> This looks very reasonable to me, but I'm not all that familiar with
> vc.el internals.  Does anybody else have any opinions on this?

It's only reasonable in buffers where default-directory is really
meaningful.  E.g. in *Help* or *info* it's likely not going to do you
much good.
So feel free to add more major modes (rather than just `dired'), but
I don't think using (vc-responsible-backend default-directory)
everywhere is a good idea.


        Stefan

bug#6870: Make vc-root-diff work in more modes

[Lars Magne Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> It's only reasonable in buffers where default-directory is really
> meaningful.  E.g. in *Help* or *info* it's likely not going to do you
> much good.
> So feel free to add more major modes (rather than just `dired'), but
> I don't think using (vc-responsible-backend default-directory)
> everywhere is a good idea.

What about all buffers that have file names?  A la

(and (buffer-file-name)
     (vc-responsible-backend default-directory))

or something along those lines...
     
-- 
(domestic pets only, the antidote for overdose, milk.)
  bloggy blog http://lars.ingebrigtsen.no/

bug#6870: Make vc-root-diff work in more modes

[Stefan Monnier]

>> It's only reasonable in buffers where default-directory is really
>> meaningful.  E.g. in *Help* or *info* it's likely not going to do you
>> much good.
>> So feel free to add more major modes (rather than just `dired'), but
>> I don't think using (vc-responsible-backend default-directory)
>> everywhere is a good idea.

> What about all buffers that have file names?  A la

> (and (buffer-file-name)
>      (vc-responsible-backend default-directory))

That'd be fine, yes.


        Stefan

bug#6870: Make vc-root-diff work in more modes

[Chong Yidong]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> What about all buffers that have file names?  A la
>
>> (and (buffer-file-name)
>>      (vc-responsible-backend default-directory))
>
> That'd be fine, yes.

But this might be confusing, since this check would not trigger for
non-file buffers generated from those file buffers.

i.e., if you have a buffer with a file name that is not handled by VC,
vc-root-diff would work for that buffer but not for a diff file
generated from that buffer.

Whereas if a buffer with a file name *is* handled by VC, vc-root-diff
would work for both that buffer and a diff file generated for that
buffer.

bug#6870: Make vc-root-diff work in more modes

[Lars Ingebrigtsen]

rogers-emacs@rgrjr.dyndns.org writes:

>    It makes sense to me that vc-root-diff uses "(vc-responsible-backend
> default-directory)" when in a dired-mode buffer.  But since vc-root-diff
> is not at all about the current buffer, why not also make that the
> default for shell-mode, diff-mode, or any of the other modes for
> non-version-controlled buffers that may be generated in a working copy?

[...]

> -		 ((derived-mode-p 'dired-mode) (vc-responsible-backend default-directory))
> -		 (vc-mode (vc-backend buffer-file-name))))
> +		 (vc-mode (vc-backend buffer-file-name))
> +		 (t (vc-responsible-backend default-directory))))

This has been extended somewhat over the years:

(defun vc-deduce-backend ()
  (cond ((derived-mode-p 'vc-dir-mode)   vc-dir-backend)
	((derived-mode-p 'log-view-mode) log-view-vc-backend)
	((derived-mode-p 'log-edit-mode) log-edit-vc-backend)
	((derived-mode-p 'diff-mode)     diff-vc-backend)
        ;; Maybe we could even use comint-mode rather than shell-mode?
	((derived-mode-p 'dired-mode 'shell-mode 'compilation-mode)
	 (ignore-errors (vc-responsible-backend default-directory)))
	(vc-mode (vc-backend buffer-file-name))))

So we still don't do this in all buffers, but since there's some issues
with that, I think this works well now.  So I'm closing this bug
report.  If there's more to be done here, respond to the debbugs address
and we'll reopen the report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no