- my ($out_r, $out_w);
- pipe($out_r, $out_w) or $self->fail("pipe failed: $!");
- my @cmd = (qw(git), "--git-dir=$self->{git_dir}",
- qw(-c core.abbrev=40 cat-file), $batch);
- my $redir = { 0 => $out_r };
+
+ state $EXE_ST = ''; # pack('dd', st_ctime, st_size);
+ my $exe = which('git') // die "git not found in $ENV{PATH}";
+ my @st = stat($exe) or die "stat: $!";
+ my $st = pack('dd', $st[10], $st[7]);
+ state $VER;
+ if ($st ne $EXE_ST) {
+ my $rd = popen_rd([ $exe, '--version' ]);
+ my $v = readline($rd);
+ $v =~ /\b([0-9]+(?:\.[0-9]+){2})/ or die
+ "$exe --version output: $v # unparseable";
+ my @v = split(/\./, $1, 3);
+ $VER = ($v[0] << 24) | ($v[1] << 16) | $v[2];
+ $EXE_ST = $st;
+ }
+
+ # git 2.31.0+ supports -c core.abbrev=no, don't bother with
+ # core.abbrev=64 since not many releases had SHA-256 prior to 2.31
+ my $abbr = $VER < (2 << 24 | 31 << 16) ? 40 : 'no';
+
+ pipe(my ($out_r, $out_w)) or $self->fail("pipe failed: $!");
+ my $rdr = { 0 => $out_r, pgid => 0 };
+ my $gd = $self->{git_dir};
+ if ($gd =~ s!/([^/]+/[^/]+)\z!/!) {
+ $rdr->{-C} = $gd;
+ $gd = $1;
+ }
+ my @cmd = ($exe, "--git-dir=$gd", '-c', "core.abbrev=$abbr",
+ 'cat-file', $batch);