[PATCH] p5303: avoid sed GNU-ism

[Jeff King <peff@peff.net>]

On Fri, Jan 29, 2021 at 02:32:50PM -0500, Jeff King wrote:

> > this construct:
> > 
> > 	... |
> > 	sed -n '1~5p' |
> > 	head -n "$1" |
> >         ...
> > 
> > which is a GNUism.  Peff often says that very small population
> > actually run our perf suite, and this seems to corroborate the
> > conjecture.
> 
> Oops. Looks like I was the one who introduced that. Nobody seems to have
> complained, so I'm somewhat tempted to leave it. But it would not be too
> hard to replace with perl, I think.

Maybe worth doing this?

-- >8 --
Subject: [PATCH] p5303: avoid sed GNU-ism

Using "1~5" isn't portable. Nobody seems to have noticed, since perhaps
people don't tend to run the perf suite on more exotic platforms. Still,
it's better to set a good example.

We can use:

  perl -ne 'print if $. % 5 == 1'

instead. But we can further observe that perl does a good job of the
other parts of this pipeline, and fold the whole thing together.

Signed-off-by: Jeff King <peff@peff.net>
---
 t/perf/p5303-many-packs.sh | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/t/perf/p5303-many-packs.sh b/t/perf/p5303-many-packs.sh
index f4c2ab0584..ce0c42cc9f 100755
--- a/t/perf/p5303-many-packs.sh
+++ b/t/perf/p5303-many-packs.sh
@@ -21,10 +21,14 @@ repack_into_n () {
 	mkdir staging &&
 
 	git rev-list --first-parent HEAD |
-	sed -n '1~5p' |
-	head -n "$1" |
-	perl -e 'print reverse <>' \
-	>pushes
+	perl -e '
+		my $n = shift;
+		while (<>) {
+			last unless @commits < $n;
+			push @commits, $_ if $. % 5 == 1;
+		}
+		print reverse @commits;
+	' "$1" >pushes
 
 	# create base packfile
 	head -n 1 pushes |
-- 
2.30.0.759.g69d54d14a7