Re: Truncating file names with Unicode characters

From: Jeff King <peff@peff.net>
Date: Jun 9, 2018, 06:23 UTC
Message-ID: <20180609062351.GC30224@sigill.intra.peff.net>
In-Reply-To: <CA+v=Qh7eiLoN4YcnSdtjL4-wp8rTjCpA85BkQD2fRoG7u=9_Fw@mail.gmail.com>

On Fri, Jun 08, 2018 at 09:25:29PM +0300, Vitaly Potyarkin wrote:

Show 8 quoted lines

> # Truncating file names with Unicode characters
> 
> When shortening file names that contain Unicode characters, git performs
> truncation without awareness of two-byte characters. That often leads to
> splitting a character in half and displaying a garbage byte that's left.
> 
> Unawareness of Unicode also means that filename length is calculated incorrectly
> and some output gets misaligned.

Yeah, I agree it would be nice for this to be more aware of multi-byte glyphs.

Unfortunately, we don't actually know what encoding the paths are in (and they might not even all be in the same encoding). But hopefully we could at least make the common case work a bit better. If we know that core.quotepath is off, then the user is expecting paths in their terminal encoding. So possibly we could just rely on i18n.logOutputEncoding at that point (which of course defaults to utf8).

If anyone is interested in working on it, the relevant code is in diff.c:show_stats(). Looks like we do a straight strlen() to get the width, which should become utf8_strwidth(). That would solve the problem where we use the wrong width.

To deal with the broken code points, I think you'd need to copy the name into a strbuf and use strbuf_utf8_replace() to truncate (it doesn't seem to be well documented, but you can grep for a few other callers).

-Peff