From: Junio C Hamano <junkio@cox.net>
Date: Sat, 28 Apr 2007 17:31:28 GMT
Subject: Re: git-svn failure when symlink added in svn
Message-ID: <7virbgjthr.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <loom.20070428T144858-521@post.gmane.org>

Is it really the redirection that is the problem?

The process seeks $fh back to the beginning, reads 5 bytes from
it (to ensure that is 'link '), and then forks to feed $fh to
git-hash-object.

Now what do you really want to hash here?  I do not know what
this "file that begins with 'link '" magic is about, but I
suspect that the child may or may not start reading from byte
offset 5 of that file, depending on how the low-level I/O is
tied to Perl.

Here is a little test script to imitate what the part in
close_file sub is doing.  What does it output on MacOS (or
whatever systems that are having the same problem)?

On a Linux box, it appears that it reads the remainder of the
file and the test script says "child says: >>12345", so I am
assuming that is what close_file sub wants to do.  If my
suspicion is correct, you would get "child says: >>link 12345",
in which case sysseek() commented out below would help,
perhaps.

-- >8 --
#!/usr/bin/perl -w

open F, ">footest";
print F "link 12345\n";
close F;

my ($fh, $buf, $n, $pid, $out);

open $fh, "<footest";
seek($fh, 0, 0);
$n = read($fh, $buf, 5);
print "read[$n]: $buf\n";

$pid = open $out , '-|';
if (!$pid) {
	my $at = tell $fh;
	print "child: at $at\n";

	# We may want to do
        #
	#	 sysseek($fh, 5, 0);
        #
        # here.

	open STDIN, '<&', $fh;
	exec qw(sed -e s/^/>>/);
}
while (my $read = <$out>) {
	print "child says: $read";
}
close ($out);
close ($fh);