Re: git-svn failure when symlink added in svn

Linus Torvalds <torvalds <at> linux-foundation.org> writes:

quoted

trying to read the wrong SHA1 file. If one outputs ce->sha1 before
        void *new = read_sha1_file(ce->sha1, &type, size);
is called, one gets different output on Linux and Mac OS X.
For Seth's example, I get 5f34b0af07646aa529b5b005cde3a9559e606210 on Linux
and e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 on Mac OS X ...

Well, 5f34b0af0 is the "bar.txt" blob, while e69de29b is the empty blob

So yeah, the printout matches the SHA1's, and the SHA1's are clearly not 
corrupted: they are just a sign of the fact that the data that was fed to 
whoever generated the SHA1's was simply different.

The SHA1 hashes are generated in the close_file() function in
git-svn.perl by forking git-hash-object -w --stdin and redirecting
STDIN to the passed filehandle. This is what goes wrong (for some
perl-internal reason?) on Mac OS X. Here is a patch that works
around that by putting the data to be hashed in a temporary file
and calling git-hash-object with a filename.

Best regards,
    Alex

From 504892b882d05bdf1fbf2325e7544f52115555d1 Mon Sep 17 00:00:00 2001

From: Alexander Klink <redacted>
Date: Sat, 28 Apr 2007 14:46:27 +0200
Subject: [PATCH] Workaround for git-svn symlink problem on Mac OS X

git-svn had a problem with creating a symlink for a file which existed
as a "real" file beforehand. See the report from Seth Falcon:
http://permalink.gmane.org/gmane.comp.version-control.git/44445
and the test patch by Eric Wong:
http://permalink.gmane.org/gmane.comp.version-control.git/44469

Apparently, the reason for this is that in this case, perl on Mac OS X
does not like the STDIN redirect in close_file() (which forks to
git-hash-object -w --stdin to create the SHA1 hash).
The workaround now creates a temporary file for the git-hash-object input
using File::Temp, calls git-hash-object -w with the filename and safely
unlinks the file afterwards.
---
 git-svn.perl |   18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/git-svn.perl b/git-svn.perl
index 077d6b3..7af45aa 100755
--- a/git-svn.perl
+++ b/git-svn.perl

@@ -2266,6 +2266,7 @@ use warnings;
 use Carp qw/croak/;
 use IO::File qw//;
 use Digest::MD5;
+use File::Temp;
 
 # file baton members: path, mode_a, mode_b, pool, fh, blob, base
 sub new {

@@ -2448,13 +2449,16 @@ sub close_file {
 			$buf eq 'link ' or die "$path has mode 120000",
 			                       "but is not a link\n";
 		}
-		defined(my $pid = open my $out,'-|') or die "Can't fork: $!\n";
-		if (!$pid) {
-			open STDIN, '<&', $fh or croak $!;
-			exec qw/git-hash-object -w --stdin/ or croak $!;
-		}
-		chomp($hash = do { local $/; <$out> });
-		close $out or croak $!;
+
+        # put the data for git-hash-object in a temporary file,
+        # as redirecting STDIN does not always work for some reason on
+        # Mac OS X
+        my ($temp_fh, $temp_filename) = mkstemp("git-hash-input-XXXXXX");
+        print $temp_fh do { local $/; <$fh> };
+
+        chomp($hash = qx(git-hash-object -w $temp_filename));
+        File::Temp::unlink0($temp_fh, $temp_filename)
+            or die "Error unlinking temporary file $temp_filename";
 		close $fh or croak $!;
 		$hash =~ /^[a-f\d]{40}$/ or die "not a sha1: $hash\n";
 		close $fb->{base} or croak $!;

-- 
1.5.2.rc0.34.gda94-dirty