Subject: Re: [PATCH] difftool: add support for an extended revision syntax

From: David Aguilar <[email-masked]>
Date: Fri, 27 Mar 2009 09:28:49 -0700

On  0, Jakub Narebski <[email-masked]> wrote:
> David Aguilar <[email-masked]> writes:
> 
> > This adds an extended revision syntax to git-difftool.
> > Users often ask "how do I compare a file against its
> > previous version" and the answer is typically a combination
> > of 'git log <file>' and 'git difftool <sha1> <sha1> <file>'.
> > 
> > [snip]
> > 
> > The extended revision syntax also expands revisions
> > that are suffixed with '!' as a convenient way to
> > see commit diffs.  Specifying only '!' is equivalent
> > to specifying 'HEAD!'.
> > 
> > This makes the following statements equivalent:
> > 
> > 	$ git difftool !
> > 	$ git difftool HEAD!
> > 	$ git difftool HEAD~ HEAD
> 
> Errr... there already exists such syntax, and it is called HEAD^!

Yup, this patch was a mistake ;)

^! does exactly what I needed and difftool supports it since
git-diff does.

I'm still interested in the file~<n> idea [though maybe not
that exact syntax] and have been reading revision.c (as Junio
suggested) to see if it can be done in a good way.

I'm still not sure if it is a good idea since the types of
users who would want it are probably better off with tighter
integration between gitk and difftool as opposed to a
convenient command-line syntax (tho I do see how it would be
useful every now and then).  Ideally, we'd want to select two
commits in gitk and compare them.  I think qgit can do that,
but it doesn't yet know about difftool (since, of course,
difftool is not in master yet).

I noticed that my patches for "add tests to difftool" and "add
the -y shortcut for --no-prompt" were in git.git's pu branch
the other day but aren't there anymore.  Was that intentional?

> (if git-difftool can accept a..b revision specification)... or not,
> as git-rev-parse(1) states:
> 
>   r1^! includes commit r1 but excludes all of its parents.
> 
> So depending on how "r1 --not r1^" and "r1 --not r1^1 r1^2" is
> interpreted by diff (which accpets points, not ranges) it might be, or
> might be not what you wanted by introducying '!' / <rev>:!
> specification...
> 
> -- 
> Jakub Narebski
> Poland
> ShadeHawk on #git

-- 

	David