Re: [PATCH] sideband: allow ANSI SGR with colon-separated subfields

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

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Hi Mantas,
>
> On Wed, 13 May 2026, grawity@nullroute.lt wrote:
>
>> From: Mantas Mikulėnas <grawity@gmail.com>
>> 
>> The SGR values used for 256-color formatting are officially defined to
>> be a single field with :-separated subfields (e.g. "\e[1;38:5:XX;40m")
>> despite the more common but kludgy use of separate values (which then
>> become context-dependent and lead to misinterpretation by incompatible
>> terminals).
>> 
>> See also: https://github.com/ThomasDickey/xterm-snapshots/blob/6380a3eaed857c182ea6cfa78cd706966b2628d0/charproc.c#L2047-L2118
>
> This change seems well-motivated and well-executed to me. Just in case
> anybody was waiting for my objections, there ain't any coming ;-)

Should I take it as an Ack?

FWIW, this patch literally flew below my radar coverage.  Thanks for
noticing.

A need for fix-up like this does makes me doubt out decision to go
with whitelisting very narrow cases that are known to be OK (and
finding that the cases were too narrow and we need to extend),
instead of rejecting known-bad cases, by the way.

Thanks.

> Ciao,
> Johannes
>
>> 
>> Signed-off-by: Mantas Mikulėnas <grawity@gmail.com>
>> ---
>>  sideband.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>> 
>> diff --git a/sideband.c b/sideband.c
>> index 04282a568e..6cf70ef6f6 100644
>> --- a/sideband.c
>> +++ b/sideband.c
>> @@ -163,6 +163,10 @@ static int handle_ansi_sequence(struct strbuf *dest, const char *src, int n)
>>  	 *
>>  	 * ESC [ [<n> [; <n>]*] m
>>  	 *
>> +	 * where <n> can be either zero-length, or a decimal number, or a
>> +	 * series of decimal numbers separated by a colon (for 256-color or
>> +	 * true-color codes).
>> +	 *
>>  	 * These are part of the Select Graphic Rendition sequences which
>>  	 * contain more than just color sequences, for more details see
>>  	 * https://en.wikipedia.org/wiki/ANSI_escape_code#SGR.
>> @@ -210,7 +214,7 @@ static int handle_ansi_sequence(struct strbuf *dest, const char *src, int n)
>>  			strbuf_add(dest, src, i + 1);
>>  			return i;
>>  		}
>> -		if (!isdigit(src[i]) && src[i] != ';')
>> +		if (!isdigit(src[i]) && src[i] != ':' && src[i] != ';')
>>  			break;
>>  	}
>>  
>> -- 
>> 2.54.0
>> 
>>