From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Rast <trast@student.ethz.ch>
Subject: Re: [PATCH (topgit) 1/2] Implement setup_pager just like in git
Date: Wed, 7 Jan 2009 13:24:44 +0100
Message-ID: <200901071324.57222.trast@student.ethz.ch>
References: <cover.1231254832.git.kirr@landau.phys.spbu.ru> <20090106203203.GA11274@lapse.rw.madduck.net> <20090107112754.GA15158@roro3>
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Cc: martin f krafft <madduck@madduck.net>, git@vger.kernel.org,
	pasky@suse.cz
To: Kirill Smelkov <kirr@landau.phys.spbu.ru>
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Kirill Smelkov wrote:
> On Tue, Jan 06, 2009 at 09:32:03PM +0100, martin f krafft wrote:
> > I find this very confusing. Why not simply
> >=20
> >   TG_PAGER=3D"${GIT_PAGER:-}"
> >   TG_PAGER=3D"${TG_PAGER:-$PAGER}"
> >=20
> > ?
>=20
> I find it confusing too, but this is needed because they usually do
> something like this
>=20
>     $ GIT_PAGER=3D'' <some-git-command>
>=20
> to force it to be pagerless.
[...]
> So I think it would be better to preserve the same semantics for `tg
> patch` callers, though it's a pity that it's hard (maybe I'm wrong ?) to
> see whether an env var is unset.

Admittedly I haven't really studied your patch, but the ${} constructs
can in fact tell empty from unset:

  $ EMPTY=3D
  $ unset UNDEFINED
  $ echo ${UNDEFINED-foo}
  foo
  $ echo ${UNDEFINED:-foo}
  foo
  $ echo ${EMPTY-foo}

  $ echo ${EMPTY:-foo}
  foo

'man bash' indeed says

  When not performing substring expansion, bash tests for a parameter
  that is unset or null; omitting the colon results in a test only for
  a parameter that is unset.

So I suppose you could use

  ${GIT_PAGER-${PAGER-less}}

or similar.

=2D-=20
Thomas Rast
trast@{inf,student}.ethz.ch


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