Subject: Re: [PATCH] Introduce git version --list-features for porcelain use

From: "Shawn O. Pearce" <[email-masked]>
Date: Thu, 31 May 2007 23:09:59 -0400

Junio C Hamano <[email-masked]> wrote:
> "Shawn O. Pearce" <[email-masked]> writes:
> 
> > As a porcelain author I'm finding it difficult to keep track of
> > what features I can use in git-gui.  Newer versions of Git have
> > newer capabilities but they don't always immediately get newer
> > version numbers that I can easily test for.
> >
> > This is a simple plumbing option that lets a porcelain ask the
> > plumbing for its capabilities, at which point the porcelain can
> > work around anything missing, or recommend to the user that they
> > upgrade their plumbing layer.
> >
> > Signed-off-by: Shawn O. Pearce <[email-masked]>
> > ---
> >
> > 	Johannes Schindelin <[email-masked]> wrote:
> > 	>
> > 	> On Wed, 30 May 2007, Alex Riesen wrote:
> > 	>
> > 	> > git-version --features?
> > 	>
> > 	> Melikes.
> >
> > 	Good?
> 
> Hmmm.  I am not sure if you want list-features in the features
> list -- how are you going to test for it?

Yes, its a recursive definition.  But its also a feature that won't
ever be removed; if list-features is here then the list-features
feature is also here.  Makes the test in t0000 a lot easier, and
its not a huge deal to say "yes, the feature that i implement is
here too".  ;-)
 
> Also I still do not understand why you want redirect-stderr.
> Are you writing for a shell-less environment?

The redirect-stderr thing grew out of the MinGW port camp.
Apparently they cannot use (or its hard to use) an important little
tool called `cat` over there.

Why cat?  Tcl is so horribly broken that to get data for both stdout
and stderr through a pipe I have to do something sick like:

	git fetch 2>&1 | cat

because in Tcl its actually:

	set rdr [open "| git fetch |& cat" r]

The |& means 2>&1| in normal shell.  But that means I have to have
a process after it to receive the data.  Normally that's cat.
But MinGW doesn't have cat.  (Nor do they have dog, but neither
does Linux...).  So I need a way to redirect output.

Dscho's patch to git.c to give me `git --redirect-stderr` is quite
simple, and makes my life in git-gui easier.  I can just require
that to use git-gui on MinGW you must have the 'redirect-stderr'
feature supported in your plumbing layer.  On non-MinGW systems I
can fallback to "&| cat" if its not supported.

-- 
Shawn.