Re: git-diff bug?

[Eli Barzilay <eli@barzilay.org>]

On Mon, Nov 2, 2020 at 12:45 PM René Scharfe <l.s.r@web.de> wrote:
>
>     $ 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

Yes, this is what I'm getting, also without a -u.  (Also on 2.29.2)


> 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.

How is it valid?  Isn't the whole point of `--ignore-blank-lines` to
do the same thing as comparing a version of the files that drops all
empty lines?

>
>     $ 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?

$ git diff --ignore-blank-lines 1 2
diff --git a/1 b/2
index fc13a35..bd05737 100644
--- a/1
+++ b/2
@@ -1,4 +1,4 @@
 aaa
 bbb
-ccc

+ccc
$ git --version
git version 2.29.2


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