Re: [PATCH 3/4] Fit to Plan 9's ANSI/POSIX compatibility layer

From: Kyohei Kadota <lufia@lufia.org>
To: Junio C Hamano <gitster@pobox.com>
Cc: "brian m. carlson" <sandals@crustytoothpaste.net>,
	lufia via GitGitGadget <gitgitgadget@gmail.com>,
	Git List <git@vger.kernel.org>
Subject: Re: [PATCH 3/4] Fit to Plan 9's ANSI/POSIX compatibility layer
Date: Mon, 10 Aug 2020 19:53:46 +0900	[thread overview]
Message-ID: <CAFMepckAe9r1O8xrQemytHoZKeyLSjEpfdH=yP=+SzKPoCOf8w@mail.gmail.com> (raw)
In-Reply-To: <xmqq5z9vlk5q.fsf@gitster.c.googlers.com>

>
> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
>
> > I will note that usually the project prefers to have a human's personal
> > name here and in the commit metadata instead of a username.  Junio may
> > chime in here with an opinion.
>
> Thanks, I just did.
>
> >>  command_list () {
> >> -    eval "grep -ve '^#' $exclude_programs" <"$1"
> >> +    eval "grep -v -e '^#' $exclude_programs" <"$1"
> >
> > Is it really the case that Plan 9's grep cannot deal with bundled short
> > options?  That seems to be a significant departure from POSIX and Unix
> > behavior.  Regardless, this should be explained in the commit message.
>
> I am not interested in this ball of wax, but there are some pieces
> that are worth salvaging.  This is one of those good bits.
>
> diff --git a/GIT-VERSION-GEN b/GIT-VERSION-GEN
> index 9db2f4feab..a7cc01caf9 100755
> --- a/GIT-VERSION-GEN
> +++ b/GIT-VERSION-GEN
> @@ -26,7 +26,7 @@ else
>         VN="$DEF_VER"
>  fi
>
> -VN=$(expr "$VN" : v*'\(.*\)')
> +VN=${VN#v}
>
>  if test -r $GVF
>  then
>
> BUT.
>
> Dealing with "grep" that cannot take "-ve" and forces developers to
> spell it as "-v -e" is not one of them.  So is forbidding use of
> "cut".

I see. I will rewrite Plan 9's ape/grep to handle bundled options well.

> >>  get_categories () {
> >> -    tr ' ' '\n'|
> >> +    tr ' ' '\012'|
> >
> > Okay, I guess.  Is this something we need to handle elsewhere as well?
> > The commit message should tell us why this is necessary, and what Plan 9
> > does and doesn't support.
>
> Yeah, POSIX does want you to understand '\n' and others, but this is
> within reason for portability that I think we could swallow.

I'm happy, thanks.

> >> +if test -z "$(echo -n)"
> >> +then
> >> +    alias print='echo -n'
> >> +else
> >> +    alias print='printf %s'
> >> +fi
> >
> > Let's avoid an alias here (especially with a common builtin name) and
> > instead use a shell function.  Maybe like this (not tab-indented):
> >
> >   print_nonl () {
> >     if command -v printf >/dev/null 2>&1
> >     then
> >       printf "%s" "$@"
> >     else
> >       echo -n "$@"
> >     fi
> >   }
>
> I'd rather not to see this done; "echo -n" and "echo '...\c'" are
> not portable and we do want people to use 'printf'.  This directly
> goes against it.
>
> > This is also going to need some patching in the testsuite, since we use
> > printf extensively (more than 1300 times).  I do hope you have perl
> > available.
>
> Eh, so what would Plan9 people do with Perl?  Write a single-liner
> 'printf' script and put it in a directory on their $PATH?
>
> I am not sure if it is worth crippling the toolset our developers
> are allowed to choose from and use in our scripts and tests like
> this patch tries to do.

Like other topics, I decide to implement printf(1).
These new POSIX tools will be installed to Plan 9 systems
from other repo or patches before building git.

> If this were Windows, it might have been a different story, but what
> we are talking about is Plan 9, which had the last "fourth edition"
> in 2002, right?  During the 18 years since then, none of its users
> and developers work on porting many OSS packages, whose primary user
> base are on POSIXy systems, to it and we need to apply patches like
> these to each and every OSS packages of interest?  I would have
> expected that any exotic-minority-but-thriving-platform would be
> able to tell its users "here are ports of POSIXy programs---install
> them and it can become usable by those who only know Linux"?
>
> So, I dunno.

Final official distribution from Bell labs was released in Jan 2015.
Now, There are some distributions that forked from official Plan 9 and
are maintained by that community,
such as 9legacy, 9front or others.

I will try to implement POSIX toolsets if it is needed because POSIX
is a large spec.
Thanks for your advice.