Re: [PATCH v3 3/3] ref-filter: use pretty.c logic for trailers

[Junio C Hamano <gitster@pobox.com>]

Hariom verma <hariom18599@gmail.com> writes:

> I suspect that "fix" for "log --pretty" isn't going to work here.
>
> Even if we apply the same "log --pretty"'s fix here. I think we still
> end up having an empty blank line between each ref item.

After sleeping on it and seeing a result of an experiment like
this one, I think that might be unavoidable.

    $ git for-each-ref \
	--format="One%0a%(trailers:key=Signed-off-by:)Two%0a" \
	refs/heads/js/range-diff-wo-dotdot
    One
    Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
    Signed-off-by: Junio C Hamano <gitster@pobox.com>
    Two
    $ exit

People who write such "Two" without prefixing it with a newline
"%0a" themselves may view such a "fix" a regression.

It is sad that this %(trailers) itself is relatively a new thing,
and I had thought that all the other ingredients are designed to
strip the trailing newline, e.g. try this:

    $ git for-each-ref \
	--format="%(subject)%0a%(trailers:key=Signed-off-by:)" \
	refs/heads/js/range-diff-wo-dotdot
    range-diff(docs): explain how to specify commit ranges
    Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
    Signed-off-by: Junio C Hamano <gitster@pobox.com>

Notice that %(subject) is followed explicitly by %0a.  I think
%(author:date), etc. would do the same.  But %(trailers) behave
differently, and that is because it expects to be multi-line and
perhaps to mimic %(body)?  In any case, it may be too late to change
its behaviour.  At least I do not think of a good waoy to do so.

By the way, when merged to 'seen' (you can try the above that shows
%(subject) followed by %(trailers) with the tip of 'seen'), it dies
like this:

    $ git for-each-ref \
	--format="%(subject)%0a%(trailers:key=Signed-off-by:)" \
	refs/heads/js/range-diff-wo-dotdot
    free(): double free detected in tcache 2
    Aborted

There must be some interaction with another topic but I didn't dig
deeper.

Thanks.