Re: [PATCH 6/8] git-prompt: add fallback for shells without $'...'

From: avih <avihpit@yahoo.com>
Date: Jul 25, 2024, 20:03 UTC
Message-ID: <511935853.2797881.1721937799082@mail.yahoo.com>
In-Reply-To: <xmqqsevxignu.fsf@gitster.g>

 On Thursday, July 25, 2024 at 07:19:56 PM GMT+3, Junio C Hamano <gitster@pobox.com> wrote:

> I think you are over-engineering this.  We do not have immediate
> need for such facility to be used by other scripts.  On the other
> hand, we know exactly what git-prompt wants to see available, and
> you already implemented them.

Yes. It was a misunderstanding on my part, and it was overengineered.

But because I initially misinterpreted your statement as "disallow $'...' at the guidelines, and we need to find one variant (form) to use", it got me thinking, because I wasn't very happy with the existing form at the patch either.

And it did eventually lead to a solution we both liked. I'm OK taking that road, but next time I should probably wait a bit more before going pulic with half-baked ideas.

> So just losing "make assignment asuming $'blah' works, and then
> reassign based on what printf gave us" and always using the printf
> thing is what we want to see here.

Yes.

> Are you sure that everybody's implementation of printf(1) is happy
> with \d and \dd?  I am an old timer who learnt in a distant past to
> always spell octals as \ddd without omitting any leading 0-digit,
> because some was unhappy.

If I knew who "everybody" is, then maybe.

But "learned in the distant past" does carry weight, as do existing practices. However, there seem to be almost no cases in non - /t/... files, and most of them are in git-prompt.sh.

In test scripts though, it's a mixed bag. I think in decreasing order
of popularity:
- Always use \ddd form.
- Allow less than 3 if it begins with 0, like \01, and many \0 .
- Yes, \1 or \4 are fine (there are not many of those).

I'll use the \ddd form you because you prefer it and it does seem the most popular (I think also outside of git codebase), and even if only for being bullet-proof against following '0'-'7' chars at the string.

But back to the question of how much I'm sure, then I'm sure there are exceptions, but I couldn't find one yet.

It works in all the shell-builtin-printf I have access to (~ 20), as well as gnu /bin/printf. Obviously there are many common ancestors there (esp. ash and pdksh), but they are still different codebases, and others don't share code with those, like ksh, bash, Schily, yash.

As a cute data point, this printf statement, copy-pasted into a 1981 BSD 2.11 running on PDP11, prints the exact output as it does today:

    printf 'a="\1" b="\2" c="\33" d="\n" e="\r\n"' | od -c

https://skn.noip.me/pdp11/pdp11.html  ("boot RP1", user root, no pass)

On Thursday, July 25, 2024 at 07:24:08 PM GMT+3, Junio C Hamano <gitster@pobox.com> wrote:

Show 8 quoted lines

> avih <avihpit@yahoo.com> writes:
> >    eval "$(printf '
> >        __git_SOH="\1" __git_STX="\2" __git_ESC="\33"
> >        __git_LF="\n" __git_CRLF="\r\n"
> >    ')"
>
> Modulo my superstition against \d and \dd, the above does look
> very readable and hard to break.

Thanks.