Re: [PATCH 2/2] diff: teach diff to read gitattribute diff-algorithm

>
> Hi Elijah
>
> On 09/02/2023 09:09, Elijah Newren wrote:
> > Hi John and Phillip,
> >
> > On Tue, Feb 7, 2023 at 9:05 AM John Cai <johncai86@gmail.com> wrote:
> >>
> > [...]
> >>> Perhaps I'm over simplifying but having read the issue you linked to I couldn't help feeling that the majority of users might be satisfied by just changing gitlab to use the patience algorithm when generating diffs.
> >>
> >> Right, I recognize this is a judgment call that may be best left up to the list.
> >>
> >> We don't have a way in GitLab to change the diff algorithm currently. Of course
> >> that can be implemented outside of Git,
> >
> > Well, the below doesn't allow users to make diffs better for
> > *individual* files of interest, but if you agree with me that we
> > should just make diffs better for all users automatically, it's a
> > two-line change in git.git that I'd love to eventually convince the
> > project to take (though obviously doing that would also require some
> > documentation changes and some good messaging in release notes and
> > whatnot).  I've used it for a good long while, and had a few dozen
> > users using this patch too, all without complaint:
>
> I'd support a change to either patience or histogram as the default
> algorithm. My personal preference would be for the patience algorithm as
> I think it generally gives nicer diffs in the cases that the two
> disagree (see below, I've tried changing diff.algorithm to histogram a
> few times and I always end up changing it back to patience pretty
> quickly). However I can see there is an advantage in having "diff" and
> "merge" use the same algorithm as users who diffing either side to the
> merge base will see the same diff that the merge is using. The histogram
> algorithm is known to produce sub-optimal diffs in certain cases[1] but
> I'm not sure how much worse it is in that respect than any of the other
> algorithms.

> To see the differences between the output of patience and histogram
> algorithms I diffed the output of "git log -p --no-merges
> --diff-algorithm=patience" and "git log -p --no-merges
> --diff-algorithm=histogram". The first three differences are
>
> - 6c065f72b8 (http: support CURLOPT_PROTOCOLS_STR, 2023-01-16)
>    In get_curl_allowed_protocols() the patience algorithm shows the
>    change in the return statement more clearly
>
> - 47cfc9bd7d (attr: add flag `--source` to work with tree-ish, 2023-01-14)
>     The histogram algorithm shows read_attr_from_index() being moved
>     whereas the patience algorithm does not making the diff easier to
>     follow.
>
> - b0226007f0 (fsmonitor: eliminate call to deprecated FSEventStream
> function, 2022-12-14)
>    In fsm_listen__stop_async() the histogram algorithm shows
>    data->shutdown_style = SHUTDOWN_EVENT;
>    being moved, which is not as clear as the patience output which
>    shows it as a context line.