Re: Bug in 'git am' when applying a broken patch

[Eric Sunshine <sunshine@sunshineco.com>]

On Mon, Jun 1, 2015 at 2:58 PM, Junio C Hamano <gitster@pobox.com> wrote:
> Subject: apply: reject a hunk that does not do anything
>
> A hunk like this in a hand-edited patch without correctly adjusting
> the line counts:
>
>      @@ -660,2 +660,2 @@ inline struct sk_buff *ieee80211_authentic...
>              auth = (struct ieee80211_authentication *)
>                      skb_put(skb, sizeof(struct ieee80211_authentication));
>      -       some old text
>      +       some new text
>      --
>      2.1.0
>
>      dev mailing list
>
> at the end of the patch does not have a good way for us to diagnose
> it as corrupt patch.  We just read two lines and discard the remainder
> as cruft, which we must do in order to ignore the e-mail footer.
>
> If the hand-edited hunk header were "@@ -660,3, +660,2", this fix
> will not help---we would just remove the old text without adding the
> enw one, and treat "+ some new text" and everything after that line

s/enw/new/

> as trailing cruft.  So it is dubious that this patch would help very
> much in practice, but it is better than nothing ;-)
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  builtin/apply.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/builtin/apply.c b/builtin/apply.c
> index 146be97..54aba4e 100644
> --- a/builtin/apply.c
> +++ b/builtin/apply.c
> @@ -1638,6 +1638,9 @@ static int parse_fragment(const char *line, unsigned long size,
>         }
>         if (oldlines || newlines)
>                 return -1;
> +       if (!deleted && !added)
> +               return -1;
> +
>         fragment->leading = leading;
>         fragment->trailing = trailing;
>
> --