git gui diff widget (was Re: [msysGit] Re: [cheetah] Questions about NOTES)

From: Steffen Prohaska <prohaska-wjoc1khpmeg@public.gmane.org>
Date: Jan 30, 2008, 07:00 UTC
Message-ID: <75E9DFB9-BE1B-4B60-921D-EE0898DFA9F3@zib.de>
In-Reply-To: <20080130040336.GN24004-o8xcbExO1WpAfugRpC6u6w@public.gmane.org>

[ I put the git list on CC and chose a new topic. ]

On Jan 30, 2008, at 5:03 AM, Shawn O. Pearce wrote:

Show 34 quoted lines

>
> Johannes Schindelin <Johannes.Schindelin-Mmb7MZpHnFY@public.gmane.org> wrote:
>> On Mon, 28 Jan 2008, Shawn O. Pearce wrote:
>>> Johannes Schindelin <Johannes.Schindelin-Mmb7MZpHnFY@public.gmane.org> wrote:
>>>>
>>>> Another thing (and this concerns you, Shawn): there is this lovely
>>>> program called git-gui, and it has most of what we will ever  
>>>> want to
>>>> drive from git-cheetah.  Is there any method to call git-gui  
>>>> such that
>>>> it performs a certain command, or is there a chance to get such a
>>>> method?
>>
>> I did not mean to remote control it, just to start it with a default
>> action, such as "diff file <xyz> to HEAD", or "diff directory  
>> <xyz> to
>> index".
>
> Oh, like we do for `git gui blame HEAD file` ?  :-)
>
> That isn't too difficult.  git-gui currently cannot show a diff of
> a directory, it can only diff a single file at a time, but yea,
> it wouldn't be hard to add a `git gui diff file` to have it open
> up and show the current difference of index<->file or HEAD<->index
> for that path.
>
> Doing a diff against a random other tree-ish, or between two random
> tree-ishes would be possible, but a lot more of a challenge.
>
> The diff viewer in git-gui isn't exactly a reusable widget.
> We'd need to refactor that so it could take patch output from any
> of the patch generating git commands.  Doing such is on my list
> of things I'd like to fix in git-gui, but I haven't had time to
> do it yet.

Hmm, I'm not sure if such a full diff viewer is the most important thing to address. Most users (especially Windows users) already have a favorite graphical diff tool and they expect a mechanism to plug it into a git workflow.

A difficulty they face is that in a git workflow they often need to diff between two trees and this case is currently not handled in a sensible way if you want to view the diffs graphically. Well you could set GIT_EXTERNAL_DIFF to a graphical tool. But then git would pop-up a new instance of your graphical tool for every single file and this is certainly not what you expect (I tried it once and immediately stopped this experiment).

I think a tool that presents the list of files with differences and can launch an external tool for one of these files would be very helpful. I started to think about a command line version, git-difftool, implementing this idea, but do not yet have code. A GUI version would be preferable for cheetah anyway. Maybe the patch viewer you sketched above could provide a way to launch an external tool for any of the files touched by the patch? If the widget would be reusable maybe it could also be used in gitk?

	Steffen