Re: git-diff bug?

From: René Scharfe <l.s.r@web.de>
Date: Nov 2, 2020, 17:45 UTC
Message-ID: <72cfef26-e986-d34c-eea4-46ec0fda2688@web.de>
In-Reply-To: <CALO-guviA4xKjUi0HfA+RLkTPPaQw7KArj__A9fKz0oP3m5MGw@mail.gmail.com>

Am 02.11.20 um 07:53 schrieb Eli Barzilay:

Show 17 quoted lines

> Is the following a bug?
>
>     $ printf "aaa\nbbb\nccc\n\n" > 1
>     $ printf "aaa\nbbb\n\nccc\n" > 2
>     $ git diff --ignore-blank-lines 1 2
>
> This shows a weird output, as if `ccc` was removed and then re-added.
> Flipping the 1 & 2 names makes it show no difference at all.  I tried
> a bunch of variants, including --minimal, and the four algorithms, and
> all show the same results.  (Similar brokenness happens with an empty
> line at the beginning on one side and after the first line on the
> other.)
>
> I'm really not sure that the following is a bug, because I see the
> same behavior from `diff` (which is what made me try git-diff, hoping
> that it would be more consistent).  (But I can't think of any rational
> that would make it not a bug.)

    $ printf "aaa\nbbb\nccc\n\n" > 1
    $ printf "aaa\nbbb\n\nccc\n" > 2

    $ diff --ignore-blank-lines -u 1 2
    --- 1	2020-11-02 18:11:04.618133008 +0100
    +++ 2	2020-11-02 18:11:04.618133008 +0100
    @@ -1,4 +1,4 @@
     aaa
     bbb
    -ccc

    +ccc
    $ diff --ignore-blank-lines -u 2 1

This matches your results. That the order makes a difference is a bit odd. Both are valid diffs of the inputs and neither one changes blank lines, though, so it doesn't look like a bug.

    $ git diff --ignore-blank-lines 1 2
    $ git diff --ignore-blank-lines 2 1
    $ git --version
    git version 2.29.2

This matches your expectation, but not your results. Which version do you use?

René