Re: [PATCH (topgit) 1/2] Implement setup_pager just like in git

Kirill Smelkov wrote:

On Tue, Jan 06, 2009 at 09:32:03PM +0100, martin f krafft wrote:

quoted

I find this very confusing. Why not simply

  TG_PAGER="${GIT_PAGER:-}"
  TG_PAGER="${TG_PAGER:-$PAGER}"

?

I find it confusing too, but this is needed because they usually do
something like this

    $ GIT_PAGER='' <some-git-command>

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=
  $ 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.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch