git: use core.abbrev=no on git 2.31+

This makes it easier to support SHA-256 inboxes in the future.
Tested with both git 2.30.2 (Debian stable) and 2.39.1

1 files changed, 23 insertions, 4 deletions

diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index c9ed48be..ff3ac40f 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -16,7 +16,7 @@ use Errno qw(EINTR EAGAIN ENOENT);
 use File::Glob qw(bsd_glob GLOB_NOSORT);
 use File::Spec ();
 use Time::HiRes qw(stat);
-use PublicInbox::Spawn qw(popen_rd spawn);
+use PublicInbox::Spawn qw(popen_rd which);
 use PublicInbox::Tmpfile;
 use IO::Poll qw(POLLIN);
 use Carp qw(croak carp);
@@ -46,7 +46,6 @@ my %GIT_ESC = (
 );
 my %ESC_GIT = map { $GIT_ESC{$_} => $_ } keys %GIT_ESC;
 
-
 # unquote pathnames used by git, see quote.c::unquote_c_style.c in git.git
 sub git_unquote ($) {
         return $_[0] unless ($_[0] =~ /\A"(.*)"\z/);
@@ -122,6 +121,26 @@ sub _bidi_pipe {
                 }
                 return;
         }
+
+        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};
@@ -129,8 +148,8 @@ sub _bidi_pipe {
                 $rdr->{-C} = $gd;
                 $gd = $1;
         }
-        my @cmd = (qw(git), "--git-dir=$gd",
-                        qw(-c core.abbrev=40 cat-file), $batch);
+        my @cmd = ($exe, "--git-dir=$gd", '-c', "core.abbrev=$abbr",
+                        'cat-file', $batch);
         if ($err) {
                 my $id = "git.$self->{git_dir}$batch.err";
                 my $fh = tmpfile($id) or $self->fail("tmpfile($id): $!");