bug#55871: Acknowledgement (27.1; vc-git.el log view 'a', 'f', 'd' do not work when following renames)

[Dmitry Gutov]

On 13/12/2022 03:23, Dmitry Gutov wrote:
> > I read your message, and I think immitating GitHub's UI is a great
> > idea, as it liberates us from having to do any kind of "pretreatment"
> > of the git log (which can be expensive for large repos).
>
> Indeed. I suppose we'll lose out in some more complex cases (e.g. if 
> --follow tracks copies, it might track the cases when several files had 
> been copied into one, including when that action spanned several 
> commits; and thus --follow could show the history of each such file), 
> but we should win in the most common cases (single-file copies and 
> renames) OOtB, which we don't have any good support for still.
>
> > We should focus in this direction to fix this issue. If I get some
> > spare time over the holidays I will try to take a look (sadly, I
> > cannot promise that will be the case...).
>
> We won't be able to put the improvement into Emacs 29 anyway (the 
> release branch has been cut, it's now bugfix-only), so there is no hurry.
>
> Let's see who gets to this first. If you wanted to finish up your patch 
> instead, I'm not going to say no either. But GitHub's approach seems 
> like it should require less (and less complex) code.

Attached is the implementation for this alternative approach.

It's Git-only, but otherwise seems to function well (with potential for 
future additions). The look of the message and the button could use some 
work, but this is the best I came up thus far.

As far as testing, it allowed following all files in Emacs's repo (that 
I have tried) to their original creation. Including etc/NEWS.29, and 
most other NEWS.*, with NEWS.28 being an exception (apparently because 
on that occasion NEWS was truncated before NEWS.28 was created).

Also important: set vc-git-print-log-follow to nil. Otherwise logs don't 
end on renames, and this feature doesn't get a chance to work.

Cheers,
Dmitry.

vc-git-file-name-changes.diff
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