Re: [RFC] column: show auto columns when pager is active

[Jeff King <peff@peff.net>]

On Tue, Oct 10, 2017 at 10:10:19AM -0400, Jeff King wrote:

> That said, I'm still puzzled why it would return zero output. Strace
> shows that the read from stdin is getting no input. I suspect this may
> have to do with how we redirect stdin in test-terminal.perl.
> 
> See 18d8c26930 (test_terminal: redirect child process' stdin to a pty,
> 2015-08-04), which claims there's some raciness with closing the
> descriptor.

Ah, yeah, I think that is it. Try:

  echo input | test_terminal sed s/^/foo:/

it will randomly succeed or fail, depending on whether sed manages to
read the input before the stdin terminal is closed.

I'm not sure of an easy way to fix test-terminal, but we could work
around it like this (which also uses "-p" to actually invoke the pager,
and uses a pager that makes it clear when it's being run):

diff --git a/t/t9002-column.sh b/t/t9002-column.sh
index 9441145bf0..d322c3b745 100755
--- a/t/t9002-column.sh
+++ b/t/t9002-column.sh
@@ -180,14 +180,14 @@ EOF
 
 test_expect_success TTY '20 columns, mode auto, pager' '
 	cat >expected <<\EOF &&
-one    seven
-two    eight
-three  nine
-four   ten
-five   eleven
-six
+paged:one    seven
+paged:two    eight
+paged:three  nine
+paged:four   ten
+paged:five   eleven
+paged:six
 EOF
-	test_terminal env PAGER="cat|cat" git column --mode=auto <lista >actual &&
+	test_terminal env PAGER="sed s/^/paged:/" sh -c "git -p column --mode=auto <lista" >actual &&
 	test_cmp expected actual
 '
 test_done

All that said, I think I'd just as soon test a real command like "git
tag", which doesn't care about reading from stdin.

-Peff