From e9a3ab8ab115a663975026c84332a1d0bdc7264b Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Fri, 6 Jan 2017 17:01:14 +0000
Subject: [PATCH] Dgit.pm: Provide git_cat_file

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 Debian/Dgit.pm | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/Debian/Dgit.pm b/Debian/Dgit.pm
index e9921d6a..314bd8c7 100644
--- a/Debian/Dgit.pm
+++ b/Debian/Dgit.pm
@@ -28,6 +28,7 @@ use IO::Handle;
 use Config;
 use Digest::SHA;
 use Data::Dumper;
+use IPC::Open2;
 
 BEGIN {
     use Exporter   ();
@@ -45,7 +46,8 @@ BEGIN {
                       waitstatusmsg failedcmd_waitstatus
 		      failedcmd_report_cmd failedcmd
                       cmdoutput cmdoutput_errok
-                      git_rev_parse git_get_ref git_for_each_ref
+                      git_rev_parse git_cat_file
+		      git_get_ref git_for_each_ref
                       git_for_each_tag_referring is_fast_fwd
                       $package_re $component_re $deliberately_re
                       $branchprefix
@@ -306,6 +308,28 @@ sub git_rev_parse ($) {
     return cmdoutput qw(git rev-parse), "$_[0]~0";
 }
 
+sub git_cat_file ($) {
+    my ($objname) = @_;
+    # => ($type, $data) or ('missing', undef)
+    our ($gcf_pid, $gcf_i, $gcf_o);
+    if (!$gcf_pid) {
+	my @cmd = qw(git cat-file --batch);
+	debugcmd "GCF|", @cmd;
+	$gcf_pid = open2 $gcf_o, $gcf_i, @cmd or die $!;
+    }
+    printdebug "GCF>| ", $objname, "\n";
+    print $gcf_i $objname, "\n" or die $!;
+    my $x = <$gcf_o>;
+    printdebug "GCF<| ", $x;
+    if ($x =~ m/ (missing)$/) { return ($1, undef); }
+    my ($type, $size) = $x =~ m/^.* (\w+) (\d+)\n/ or die "$objname ?";
+    my $data;
+    (read $gcf_o, $data, $size) == $size or die "$objname $!";
+    $x = <$gcf_o>;
+    $x eq "\n" or die "$objname ($_) $!";
+    return ($type, $data);
+}
+
 sub git_for_each_ref ($$;$) {
     my ($pattern,$func,$gitdir) = @_;
     # calls $func->($objid,$objtype,$fullrefname,$reftail);
-- 
2.30.2