git-svn: handle empty files marked as symlinks in SVN

Broken SVN clients generate empty files with the svn:special set
to '*'.  This attempts to denote a symlink pointing to a file
with an empty path (""), which cannot be generated on a POSIX
system.

Thus, we mimic the behavior of svn(1) and create a zero-byte
file in our tree.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

git-svn.perl

@@ -3200,7 +3200,10 @@ sub new {
 	my ($class, $git_svn) = @_;
 	my $self = SVN::Delta::Editor->new;
 	bless $self, $class;
-	$self->{c} = $git_svn->{last_commit} if exists $git_svn->{last_commit};
+	if (exists $git_svn->{last_commit}) {
+		$self->{c} = $git_svn->{last_commit};
+		$self->{empty_symlinks} = _mark_empty_symlinks($git_svn);
+	}
 	$self->{empty} = {};
 	$self->{dir_prop} = {};
 	$self->{file_prop} = {};
@@ -3210,6 +3213,34 @@ sub new {
 	$self;
 }
 
+# this uses the Ra object, so it must be called before do_{switch,update},
+# not inside them (when the Git::SVN::Fetcher object is passed) to
+# do_{switch,update}
+sub _mark_empty_symlinks {
+	my ($git_svn) = @_;
+	my %ret;
+	my ($rev, $cmt) = $git_svn->last_rev_commit;
+	return {} unless ($rev && $cmt);
+
+	chomp(my $empty_blob = `git hash-object -t blob --stdin < /dev/null`);
+	my ($ls, $ctx) = command_output_pipe(qw/ls-tree -r -z/, $cmt);
+	local $/ = "\0";
+	my $pfx = $git_svn->{path};
+	$pfx .= '/' if length($pfx);
+	while (<$ls>) {
+		chomp;
+		s/\A100644 blob $empty_blob\t//o or next;
+		my $path = $_;
+		my (undef, $props) =
+		               $git_svn->ra->get_file($pfx.$path, $rev, undef);
+		if ($props->{'svn:special'}) {
+			$ret{$path} = 1;
+		}
+	}
+	command_close_pipe($ls, $ctx);
+	\%ret;
+}
+
 sub set_path_strip {
 	my ($self, $path) = @_;
 	$self->{path_strip} = qr/^\Q$path\E(\/|$)/ if length $path;
@@ -3268,6 +3299,9 @@ sub open_file {
 	unless (defined $mode && defined $blob) {
 		die "$path was not found in commit $self->{c} (r$rev)\n";
 	}
+	if ($mode eq '100644' && $self->{empty_symlinks}->{$path}) {
+		$mode = '120000';
+	}
 	{ path => $path, mode_a => $mode, mode_b => $mode, blob => $blob,
 	  pool => SVN::Pool->new, action => 'M' };
 }
@@ -3346,7 +3380,10 @@ sub apply_textdelta {
 	open my $dup, '<&', $fh or croak $!;
 	my $base = $::_repository->temp_acquire('git_blob');
 	if ($fb->{blob}) {
-		print $base 'link ' if ($fb->{mode_a} == 120000);
+		if ($fb->{mode_a} eq '120000' &&
+		    ! $self->{empty_symlinks}->{$fb->{path}}) {
+			print $base 'link ' or die "print $!\n";
+		}
 		my $size = $::_repository->cat_blob($fb->{blob}, $base);
 		die "Failed to read object $fb->{blob}" if ($size < 0);
 
@@ -3379,11 +3416,19 @@ sub close_file {
 		}
 		if ($fb->{mode_b} == 120000) {
 			sysseek($fh, 0, 0) or croak $!;
-			sysread($fh, my $buf, 5) == 5 or croak $!;
+			my $rd = sysread($fh, my $buf, 5);
 
-			unless ($buf eq 'link ') {
+			if (!defined $rd) {
+				croak "sysread: $!\n";
+			} elsif ($rd == 0) {
 				warn "$path has mode 120000",
-						" but is not a link\n";
+				     " but it points to nothing\n",
+				     "converting to an empty file with mode",
+				     " 100644\n";
+				$fb->{mode_b} = '100644';
+			} elsif ($buf ne 'link ') {
+				warn "$path has mode 120000",
+				     " but is not a link\n";
 			} else {
 				my $tmp_fh = $::_repository->temp_acquire(
 					'svn_hash');

t/t9131-git-svn-empty-symlink.sh

@@ -0,0 +1,90 @@
+#!/bin/sh
+
+test_description='test that git handles an svn repository with empty symlinks'
+
+. ./lib-git-svn.sh
+test_expect_success 'load svn dumpfile' '
+	svnadmin load "$rawsvnrepo" <<EOF
+SVN-fs-dump-format-version: 2
+
+UUID: 60780f9a-7df5-43b4-83ab-60e2c0673ef7
+
+Revision-number: 0
+Prop-content-length: 56
+Content-length: 56
+
+K 8
+svn:date
+V 27
+2008-11-26T07:17:27.590577Z
+PROPS-END
+
+Revision-number: 1
+Prop-content-length: 111
+Content-length: 111
+
+K 7
+svn:log
+V 4
+test
+K 10
+svn:author
+V 12
+normalperson
+K 8
+svn:date
+V 27
+2008-11-26T07:18:03.511836Z
+PROPS-END
+
+Node-path: bar
+Node-kind: file
+Node-action: add
+Prop-content-length: 33
+Text-content-length: 0
+Text-content-md5: d41d8cd98f00b204e9800998ecf8427e
+Content-length: 33
+
+K 11
+svn:special
+V 1
+*
+PROPS-END
+
+Revision-number: 2
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 13
+bar => doink
+
+K 10
+svn:author
+V 12
+normalperson
+K 8
+svn:date
+V 27
+2008-11-27T03:55:31.601672Z
+PROPS-END
+
+Node-path: bar
+Node-kind: file
+Node-action: change
+Text-content-length: 10
+Text-content-md5: 92ca4fe7a9721f877f765c252dcd66c9
+Content-length: 10
+
+link doink
+
+EOF
+'
+
+test_expect_success 'clone using git svn' 'git svn clone -r1 "$svnrepo" x'
+test_expect_success '"bar" is an empty file' 'test -f x/bar && ! test -s x/bar'
+test_expect_success 'get "bar" => symlink fix from svn' \
+		'(cd x && git svn rebase)'
+test_expect_success '"bar" becomes a symlink' 'test -L x/bar'
+test_done