Re: [PATCH v4 1/2] diff.c: When appropriate, use utf8_strwidth(), part1

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 7, 2022, 18:31 UTC
Message-ID: <xmqqedwnujce.fsf@gitster.g>
In-Reply-To: <20220907043040.idqqivi3jt35jyst@tb-raspi4>

Torsten Bögershausen <tboegi@web.de> writes:

Show 9 quoted lines

>
> OK - the comment can be removed.
>
> I didn't know how to read this comment:
>>...but the former may chomp a single multi-byte letter in the middle,
>> which would need to be corrected as a part of this change.
>
> After diffing into the code some more times, I think that we don't
> chomp a single byte out of an UTF-8 sequence.

When turning a/b/c vs a/B/c into a/{b->B}/c, two steps are involved. Take common prefix and suffix (in this case 'a' and 'c') and turn 'b' vs 'B' into {b->B} is one step. The other is what to do when prefix and suffix are long. After turning aaaaa/b/c vs aaaaa/B/c into aaaaa/{b->B}/c, if the result is overly long, how we shorten the prefix (i.e. aaaaa) and the suffix?

I knew the code that produces {b->B} honored '/' boundary, but I just did not remember offhand what diff.c::pprint_rename() did in its latter half, specifically, if it just chomped pfx and sfx as a sequence of bytes (which would have been wrong) or insisted that the common sequence search honors '/' boundary (which would be OK, as byte '/' will not appear in the middle of a single multi-byte UTF-8 "letter"). I think iti s doing the latter, so it should be fine.

Thanks.