Fix symlink handling in git-svn, related to PerlIO

After reading the leading contents from a symlink data obtained
from subversion, which we expect to begin with 'link ', the code
forked to hash the remainder (which should match readlink()
result) using git-hash-objects, by redirecting its STDIN from
the filehandle we read that 'link ' from.  This was Ok with Perl
on modern Linux, but on Mac OS, the read in the parent process
slurped more than we asked for in stdio buffer, and the child
did not correctly see the "remainder".

This attempts to fix the issue by using lower level sysseek and
sysread instead of seek and read to bypass the stdio buffer.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Acked-by: Eric Wong <normalperson@yhbt.net>
Acked-by: Seth Falcon <sethfalcon@gmail.com>

diff --git a/git-svn.perl b/git-svn.perl
index 4be85768949f037a0a91c2b8a4ff9ce0e220ade3..6f509f85e45beb03ff9030ce76d36dbd23aefaee 100755 (executable)
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -2470,9 +2470,9 @@ sub close_file {
                my $got = $md5->hexdigest;
                die "Checksum mismatch: $path\n",
                    "expected: $exp\n    got: $got\n" if ($got ne $exp);
-               seek($fh, 0, 0) or croak $!;
+               sysseek($fh, 0, 0) or croak $!;
                if ($fb->{mode_b} == 120000) {
-                       read($fh, my $buf, 5) == 5 or croak $!;
+                       sysread($fh, my $buf, 5) == 5 or croak $!;
                        $buf eq 'link ' or die "$path has mode 120000",
                                               "but is not a link\n";
                }