Re: [PATCH] patch-id: ignore newline at end of file in diff_flush_patch_id()

>
> Whitespace is ignored when calculating patch IDs.  This is done by
> removing all whitespace from diff lines before hashing them, including
> a newline at the end of a file.  If that newline is missing, however,
> diff reports that fact in a separate line containing "\ No newline at
> end of file\n", and this marker is hashed like a context line.
>
> This goes against our goal of making patch IDs independent of
> whitespace.  Use the same heuristic that 2485eab55cc (git-patch-id: do
> not trip over "no newline" markers, 2011-02-17) added to git patch-id
> instead and skip diff lines that start with a backslash and a space
> and are longer than twelve characters.
>
> Reported-by: Tilman Vogel <tilman.vogel@web.de>
> Initial-test-by: Tilman Vogel <tilman.vogel@web.de>
> Signed-off-by: René Scharfe <l.s.r@web.de>
> ---
>  diff.c            |  2 ++
>  t/t3500-cherry.sh | 23 +++++++++++++++++++++++
>  2 files changed, 25 insertions(+)
>
> diff --git a/diff.c b/diff.c
> index f9709de7b45..f175019eb7a 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -6044,6 +6044,8 @@ static void patch_id_consume(void *priv, char *line, unsigned long len)
>         struct patch_id_t *data = priv;
>         int new_len;
>
> +       if (len > 12 && starts_with(line, "\\ "))
> +               return;
>         new_len = remove_space(line, len);
>
>         the_hash_algo->update_fn(data->ctx, line, new_len);
> diff --git a/t/t3500-cherry.sh b/t/t3500-cherry.sh
> index f038f34b7c0..2b8d9cb38ed 100755
> --- a/t/t3500-cherry.sh
> +++ b/t/t3500-cherry.sh
> @@ -55,4 +55,27 @@ test_expect_success \
>       expr "$(echo $(git cherry master my-topic-branch) )" : "+ [^ ]* - .*"
>  '
>
> +test_expect_success 'cherry ignores whitespace' '
> +       git switch --orphan=upstream-with-space &&
> +       test_commit initial file &&
> +       >expect &&
> +       git switch --create=feature-without-space &&
> +
> +       # A spaceless file on the feature branch.  Expect a match upstream.
> +       printf space >file &&
> +       git add file &&
> +       git commit -m"file without space" &&
> +       git log --format="- %H" -1 >>expect &&
> +
> +       # A further change.  Should not match upstream.
> +       test_commit change file &&
> +       git log --format="+ %H" -1 >>expect &&
> +
> +       git switch upstream-with-space &&
> +       # Same as the spaceless file, just with spaces and on upstream.
> +       test_commit "file with space" file "s p a c e" file-with-space &&
> +       git cherry upstream-with-space feature-without-space >actual &&
> +       test_cmp expect actual
> +'
> +
>  test_done
> --
> 2.28.0