From: Junio C Hamano <gitster@pobox.com>
Date: Mon, 26 Nov 2018 04:02:30 GMT
Subject: Re: BUG: CR marker ^M doesn't show up in '-' lines of diffs when the ending of the removed line is CR+LF
Message-ID: <xmqqr2f8zdt5.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <30442f9c-a1cb-4635-d8e3-a301d94a56fd@kdbg.org>

Johannes Sixt <j6t@kdbg.org> writes:

> But incorrect whitespace is never highlighted in removed lines, why
> should CR be an exception?
> ...
> Same here for other cases, for example
> 
> -something<SP>
> +something
>
> will not have on obvious indicator that whitespace was corrected.

All correct, but misses one point in Frank's original report, which
observed

	-something
	+something_new^M

with ^M highlighted for whitespace error.  The highlighting is
correct.  But notice lack of caret-em on the preimage line?

It turns out that we show something like this

    <RED>-something<RESET> CR LF

for the preimage line, while showing something like this

    <GREEN>+something_new<RESET><BG-RED> CR <RESET> LF

for the postimage line.  

Because CR on the postimage line, thanks to highlighting, appears
alone separate from the LF, it is shown as two-letter caret-em
sequence to the user.

On the other hand, because CR and LF appear next to each other on
the preimage line, the pager and/or the terminal behaves as if CR is
not even there and that is where Frank's complaint comes from, I think.

The code is doing the right thing by showing CR, but it is hidden by
the pager and/or the terminal.