Introducing contrib/git-svn.

2 files changed, 978 insertions, 0 deletions

diff --git a/contrib/git-svn/git-svn b/contrib/git-svn/git-svn
new file mode 100755
index 000000000..62fc14fb0
--- /dev/null
+++ b/contrib/git-svn/git-svn
@@ -0,0 +1,770 @@
+#!/usr/bin/env perl
+use warnings;
+use strict;
+use vars qw/	$AUTHOR $VERSION
+		$SVN_URL $SVN_INFO $SVN_WC
+		$GIT_SVN_INDEX $GIT_SVN
+		$GIT_DIR $REV_DIR/;
+$AUTHOR = 'Eric Wong <normalperson@yhbt.net>';
+$VERSION = '0.9.0';
+$GIT_DIR = $ENV{GIT_DIR} || "$ENV{PWD}/.git";
+$GIT_SVN = $ENV{GIT_SVN_ID} || 'git-svn';
+$GIT_SVN_INDEX = "$GIT_DIR/$GIT_SVN/index";
+$ENV{GIT_DIR} ||= $GIT_DIR;
+$SVN_URL = undef;
+$REV_DIR = "$GIT_DIR/$GIT_SVN/revs";
+$SVN_WC = "$GIT_DIR/$GIT_SVN/tree";
+
+# make sure the svn binary gives consistent output between locales and TZs:
+$ENV{TZ} = 'UTC';
+$ENV{LC_ALL} = 'C';
+
+# If SVN:: library support is added, please make the dependencies
+# optional and preserve the capability to use the command-line client.
+# See what I do with XML::Simple to make the dependency optional.
+use Carp qw/croak/;
+use IO::File qw//;
+use File::Basename qw/dirname basename/;
+use File::Path qw/mkpath/;
+use Getopt::Long qw/:config gnu_getopt no_ignore_case auto_abbrev/;
+use File::Spec qw//;
+my $sha1 = qr/[a-f\d]{40}/;
+my $sha1_short = qr/[a-f\d]{6,40}/;
+my ($_revision,$_stdin,$_no_ignore_ext,$_no_stop_copy,$_help,$_rmdir,$_edit);
+
+GetOptions(	'revision|r=s' => \$_revision,
+		'no-ignore-externals' => \$_no_ignore_ext,
+		'stdin|' => \$_stdin,
+		'edit|e' => \$_edit,
+		'rmdir' => \$_rmdir,
+		'help|H|h' => \$_help,
+		'no-stop-copy' => \$_no_stop_copy );
+my %cmd = (
+	fetch => [ \&fetch, "Download new revisions from SVN" ],
+	init => [ \&init, "Initialize and fetch (import)"],
+	commit => [ \&commit, "Commit git revisions to SVN" ],
+	rebuild => [ \&rebuild, "Rebuild git-svn metadata (after git clone)" ],
+	help => [ \&usage, "Show help" ],
+);
+my $cmd;
+for (my $i = 0; $i < @ARGV; $i++) {
+	if (defined $cmd{$ARGV[$i]}) {
+		$cmd = $ARGV[$i];
+		splice @ARGV, $i, 1;
+		last;
+	}
+};
+
+# we may be called as git-svn-(command), or git-svn(command).
+foreach (keys %cmd) {
+	if (/git\-svn\-?($_)(?:\.\w+)?$/) {
+		$cmd = $1;
+		last;
+	}
+}
+usage(0) if $_help;
+usage(1) unless (defined $cmd);
+svn_check_ignore_externals();
+$cmd{$cmd}->[0]->(@ARGV);
+exit 0;
+
+####################### primary functions ######################
+sub usage {
+	my $exit = shift || 0;
+	my $fd = $exit ? \*STDERR : \*STDOUT;
+	print $fd <<"";
+git-svn - bidirectional operations between a single Subversion tree and git
+Usage: $0 <command> [options] [arguments]\n
+Available commands:
+
+	foreach (sort keys %cmd) {
+		print $fd '  ',pack('A10',$_),$cmd{$_}->[1],"\n";
+	}
+	print $fd <<"";
+\nGIT_SVN_ID may be set in the environment to an arbitrary identifier if
+you're tracking multiple SVN branches/repositories in one git repository
+and want to keep them separate.
+
+	exit $exit;
+}
+
+sub rebuild {
+	$SVN_URL = shift or undef;
+	my $repo_uuid;
+	my $newest_rev = 0;
+
+	my $pid = open(my $rev_list,'-|');
+	defined $pid or croak $!;
+	if ($pid == 0) {
+		exec("git-rev-list","$GIT_SVN-HEAD") or croak $!;
+	}
+	my $first;
+	while (<$rev_list>) {
+		chomp;
+		my $c = $_;
+		croak "Non-SHA1: $c\n" unless $c =~ /^$sha1$/o;
+		my @commit = grep(/^git-svn-id: /,`git-cat-file commit $c`);
+		next if (!@commit); # skip merges
+		my $id = $commit[$#commit];
+		my ($url, $rev, $uuid) = ($id =~ /^git-svn-id:\s(\S+?)\@(\d+)
+						\s([a-f\d\-]+)$/x);
+		if (!$rev || !$uuid || !$url) {
+			# some of the original repositories I made had
+			# indentifiers like this:
+			($rev, $uuid) = ($id =~/^git-svn-id:\s(\d+)
+							\@([a-f\d\-]+)/x);
+			if (!$rev || !$uuid) {
+				croak "Unable to extract revision or UUID from ",
+					"$c, $id\n";
+			}
+		}
+		print "r$rev = $c\n";
+		unless (defined $first) {
+			if (!$SVN_URL && !$url) {
+				croak "SVN repository location required: $url\n";
+			}
+			$SVN_URL ||= $url;
+			$repo_uuid = setup_git_svn();
+			$first = $rev;
+		}
+		if ($uuid ne $repo_uuid) {
+			croak "Repository UUIDs do not match!\ngot: $uuid\n",
+						"expected: $repo_uuid\n";
+		}
+		assert_revision_eq_or_unknown($rev, $c);
+		sys('git-update-ref',"$GIT_SVN/revs/$rev",$c);
+		$newest_rev = $rev if ($rev > $newest_rev);
+	}
+	close $rev_list or croak $?;
+	if (!chdir $SVN_WC) {
+		my @svn_co = ('svn','co',"-r$first");
+		push @svn_co, '--ignore-externals' unless $_no_ignore_ext;
+		sys(@svn_co, $SVN_URL, $SVN_WC);
+		chdir $SVN_WC or croak $!;
+	}
+
+	$pid = fork;
+	defined $pid or croak $!;
+	if ($pid == 0) {
+		my @svn_up = qw(svn up);
+		push @svn_up, '--ignore-externals' unless $_no_ignore_ext;
+		sys(@svn_up,"-r$newest_rev");
+		$ENV{GIT_INDEX_FILE} = $GIT_SVN_INDEX;
+		git_addremove();
+		exec('git-write-tree');
+	}
+	waitpid $pid, 0;
+}
+
+sub init {
+	$SVN_URL = shift or croak "SVN repository location required\n";
+	unless (-d $GIT_DIR) {
+		sys('git-init-db');
+	}
+	setup_git_svn();
+}
+
+sub fetch {
+	my (@parents) = @_;
+	$SVN_URL ||= file_to_s("$GIT_DIR/$GIT_SVN/info/url");
+	my @log_args = -d $SVN_WC ? ($SVN_WC) : ($SVN_URL);
+	if (-d $SVN_WC && !$_revision) {
+		$_revision = 'BASE:HEAD';
+	}
+	push @log_args, "-r$_revision" if $_revision;
+	push @log_args, '--stop-on-copy' unless $_no_stop_copy;
+
+	eval { require XML::Simple or croak $! };
+	my $svn_log = $@ ? svn_log_raw(@log_args) : svn_log_xml(@log_args);
+
+	my $base = shift @$svn_log or croak "No base revision!\n";
+	my $last_commit = undef;
+	unless (-d $SVN_WC) {
+		my @svn_co = ('svn','co',"-r$base->{revision}");
+		push @svn_co,'--ignore-externals' unless $_no_ignore_ext;
+		sys(@svn_co, $SVN_URL, $SVN_WC);
+		chdir $SVN_WC or croak $!;
+		$last_commit = git_commit($base, @parents);
+		unless (-f "$GIT_DIR/refs/heads/master") {
+			sys(qw(git-update-ref refs/heads/master),$last_commit);
+		}
+		assert_svn_wc_clean($base->{revision}, $last_commit);
+	} else {
+		chdir $SVN_WC or croak $!;
+		$last_commit = file_to_s("$REV_DIR/$base->{revision}");
+	}
+	my @svn_up = qw(svn up);
+	push @svn_up, '--ignore-externals' unless $_no_ignore_ext;
+	my $last_rev = $base->{revision};
+	foreach my $log_msg (@$svn_log) {
+		assert_svn_wc_clean($last_rev, $last_commit);
+		$last_rev = $log_msg->{revision};
+		sys(@svn_up,"-r$last_rev");
+		$last_commit = git_commit($log_msg, $last_commit, @parents);
+	}
+	assert_svn_wc_clean($last_rev, $last_commit);
+	return pop @$svn_log;
+}
+
+sub commit {
+	my (@commits) = @_;
+	if ($_stdin || !@commits) {
+		print "Reading from stdin...\n";
+		@commits = ();
+		while (<STDIN>) {
+			if (/^([a-f\d]{6,40})\b/) {
+				unshift @commits, $1;
+			}
+		}
+	}
+	my @revs;
+	foreach (@commits) {
+		push @revs, (safe_qx('git-rev-parse',$_));
+	}
+	chomp @revs;
+
+	fetch();
+	chdir $SVN_WC or croak $!;
+	my $svn_current_rev =  svn_info('.')->{'Last Changed Rev'};
+	foreach my $c (@revs) {
+		print "Committing $c\n";
+		svn_checkout_tree($svn_current_rev, $c);
+		$svn_current_rev = svn_commit_tree($svn_current_rev, $c);
+	}
+	print "Done committing ",scalar @revs," revisions to SVN\n";
+
+}
+
+########################### utility functions #########################
+
+sub setup_git_svn {
+	defined $SVN_URL or croak "SVN repository location required\n";
+	unless (-d $GIT_DIR) {
+		croak "GIT_DIR=$GIT_DIR does not exist!\n";
+	}
+	mkpath(["$GIT_DIR/$GIT_SVN"]);
+	mkpath(["$GIT_DIR/$GIT_SVN/info"]);
+	mkpath([$REV_DIR]);
+	s_to_file($SVN_URL,"$GIT_DIR/$GIT_SVN/info/url");
+	my $uuid = svn_info($SVN_URL)->{'Repository UUID'} or
+					croak "Repository UUID unreadable\n";
+	s_to_file($uuid,"$GIT_DIR/$GIT_SVN/info/uuid");
+
+	open my $fd, '>>', "$GIT_DIR/$GIT_SVN/info/exclude" or croak $!;
+	print $fd '.svn',"\n";
+	close $fd or croak $!;
+	return $uuid;
+}
+
+sub assert_svn_wc_clean {
+	my ($svn_rev, $commit) = @_;
+	croak "$svn_rev is not an integer!\n" unless ($svn_rev =~ /^\d+$/);
+	croak "$commit is not a sha1!\n" unless ($commit =~ /^$sha1$/o);
+	my $svn_info = svn_info('.');
+	if ($svn_rev != $svn_info->{'Last Changed Rev'}) {
+		croak "Expected r$svn_rev, got r",
+				$svn_info->{'Last Changed Rev'},"\n";
+	}
+	my @status = grep(!/^Performing status on external/,(`svn status`));
+	@status = grep(!/^\s*$/,@status);
+	if (scalar @status) {
+		print STDERR "Tree ($SVN_WC) is not clean:\n";
+		print STDERR $_ foreach @status;
+		croak;
+	}
+	my ($tree_a) = grep(/^tree $sha1$/o,`git-cat-file commit $commit`);
+	$tree_a =~ s/^tree //;
+	chomp $tree_a;
+	chomp(my $tree_b = `GIT_INDEX_FILE=$GIT_SVN_INDEX git-write-tree`);
+	if ($tree_a ne $tree_b) {
+		croak "$svn_rev != $commit, $tree_a != $tree_b\n";
+	}
+}
+
+sub parse_diff_tree {
+	my $diff_fh = shift;
+	local $/ = "\0";
+	my $state = 'meta';
+	my @mods;
+	while (<$diff_fh>) {
+		chomp $_; # this gets rid of the trailing "\0"
+		print $_,"\n";
+		if ($state eq 'meta' && /^:(\d{6})\s(\d{6})\s
+					$sha1\s($sha1)\s([MTCRAD])\d*$/xo) {
+			push @mods, {	mode_a => $1, mode_b => $2,
+					sha1_b => $3, chg => $4 };
+			if ($4 =~ /^(?:C|R)$/) {
+				$state = 'file_a';
+			} else {
+				$state = 'file_b';
+			}
+		} elsif ($state eq 'file_a') {
+			my $x = $mods[$#mods] or croak __LINE__,": Empty array\n";
+			if ($x->{chg} !~ /^(?:C|R)$/) {
+				croak __LINE__,": Error parsing $_, $x->{chg}\n";
+			}
+			$x->{file_a} = $_;
+			$state = 'file_b';
+		} elsif ($state eq 'file_b') {
+			my $x = $mods[$#mods] or croak __LINE__,": Empty array\n";
+			if (exists $x->{file_a} && $x->{chg} !~ /^(?:C|R)$/) {
+				croak __LINE__,": Error parsing $_, $x->{chg}\n";
+			}
+			if (!exists $x->{file_a} && $x->{chg} =~ /^(?:C|R)$/) {
+				croak __LINE__,": Error parsing $_, $x->{chg}\n";
+			}
+			$x->{file_b} = $_;
+			$state = 'meta';
+		} else {
+			croak __LINE__,": Error parsing $_\n";
+		}
+	}
+	close $diff_fh or croak $!;
+	return \@mods;
+}
+
+sub svn_check_prop_executable {
+	my $m = shift;
+	if ($m->{mode_b} =~ /755$/ && $m->{mode_a} !~ /755$/) {
+		sys(qw(svn propset svn:executable 1), $m->{file_b});
+	} elsif ($m->{mode_b} !~ /755$/ && $m->{mode_a} =~ /755$/) {
+		sys(qw(svn propdel svn:executable), $m->{file_b});
+	}
+}
+
+sub svn_ensure_parent_path {
+	my $dir_b = dirname(shift);
+	svn_ensure_parent_path($dir_b) if ($dir_b ne File::Spec->curdir);
+	mkpath([$dir_b]) unless (-d $dir_b);
+	sys(qw(svn add -N), $dir_b) unless (-d "$dir_b/.svn");
+}
+
+sub svn_checkout_tree {
+	my ($svn_rev, $commit) = @_;
+	my $from = file_to_s("$REV_DIR/$svn_rev");
+	assert_svn_wc_clean($svn_rev,$from);
+	print "diff-tree '$from' '$commit'\n";
+	my $pid = open my $diff_fh, '-|';
+	defined $pid or croak $!;
+	if ($pid == 0) {
+		exec(qw(git-diff-tree -z -r -C), $from, $commit) or croak $!;
+	}
+	my $mods = parse_diff_tree($diff_fh);
+	unless (@$mods) {
+		# git can do empty commits, SVN doesn't allow it...
+		return $svn_rev;
+	}
+	my %rm;
+	foreach my $m (@$mods) {
+		if ($m->{chg} eq 'C') {
+			svn_ensure_parent_path( $m->{file_b} );
+			sys(qw(svn cp),		$m->{file_a}, $m->{file_b});
+			blob_to_file(		$m->{sha1_b}, $m->{file_b});
+			svn_check_prop_executable($m);
+		} elsif ($m->{chg} eq 'D') {
+			$rm{dirname $m->{file_b}}->{basename $m->{file_b}} = 1;
+			sys(qw(svn rm --force), $m->{file_b});
+		} elsif ($m->{chg} eq 'R') {
+			svn_ensure_parent_path( $m->{file_b} );
+			sys(qw(svn mv --force), $m->{file_a}, $m->{file_b});
+			blob_to_file(		$m->{sha1_b}, $m->{file_b});
+			svn_check_prop_executable($m);
+			$rm{dirname $m->{file_a}}->{basename $m->{file_a}} = 1;
+		} elsif ($m->{chg} eq 'M') {
+			if ($m->{mode_b} =~ /^120/ && $m->{mode_a} =~ /^120/) {
+				unlink $m->{file_b} or croak $!;
+				blob_to_symlink($m->{sha1_b}, $m->{file_b});
+			} else {
+				blob_to_file($m->{sha1_b}, $m->{file_b});
+			}
+			svn_check_prop_executable($m);
+		} elsif ($m->{chg} eq 'T') {
+			sys(qw(svn rm --force),$m->{file_b});
+			if ($m->{mode_b} =~ /^120/ && $m->{mode_a} =~ /^100/) {
+				blob_to_symlink($m->{sha1_b}, $m->{file_b});
+			} else {
+				blob_to_file($m->{sha1_b}, $m->{file_b});
+			}
+			svn_check_prop_executable($m);
+			sys(qw(svn add --force), $m->{file_b});
+		} elsif ($m->{chg} eq 'A') {
+			svn_ensure_parent_path( $m->{file_b} );
+			blob_to_file(		$m->{sha1_b}, $m->{file_b});
+			if ($m->{mode_b} =~ /755$/) {
+				chmod 0755, $m->{file_b};
+			}
+			sys(qw(svn add --force), $m->{file_b});
+		} else {
+			croak "Invalid chg: $m->{chg}\n";
+		}
+	}
+	if ($_rmdir) {
+		my $old_index = $ENV{GIT_INDEX_FILE};
+		$ENV{GIT_INDEX_FILE} = $GIT_SVN_INDEX;
+		foreach my $dir (keys %rm) {
+			my $files = $rm{$dir};
+			my @files;
+			foreach (safe_qx('svn','ls',$dir)) {
+				chomp;
+				push @files, $_ unless $files->{$_};
+			}
+			sys(qw(svn rm),$dir) unless @files;
+		}
+		if ($old_index) {
+			$ENV{GIT_INDEX_FILE} = $old_index;
+		} else {
+			delete $ENV{GIT_INDEX_FILE};
+		}
+	}
+}
+
+sub svn_commit_tree {
+	my ($svn_rev, $commit) = @_;
+	my $commit_msg = "$GIT_DIR/$GIT_SVN/.svn-commit.tmp.$$";
+	open my $msg, '>', $commit_msg  or croak $!;
+
+	chomp(my $type = `git-cat-file -t $commit`);
+	if ($type eq 'commit') {
+		my $pid = open my $msg_fh, '-|';
+		defined $pid or croak $!;
+
+		if ($pid == 0) {
+			exec(qw(git-cat-file commit), $commit) or croak $!;
+		}
+		my $in_msg = 0;
+		while (<$msg_fh>) {
+			if (!$in_msg) {
+				$in_msg = 1 if (/^\s*$/);
+			} else {
+				print $msg $_ or croak $!;
+			}
+		}
+		close $msg_fh or croak $!;
+	}
+	close $msg or croak $!;
+
+	if ($_edit || ($type eq 'tree')) {
+		my $editor = $ENV{VISUAL} || $ENV{EDITOR} || 'vi';
+		system($editor, $commit_msg);
+	}
+	my @ci_output = safe_qx(qw(svn commit -F),$commit_msg);
+	my ($committed) = grep(/^Committed revision \d+\./,@ci_output);
+	unlink $commit_msg;
+	defined $committed or croak
+			"Commit output failed to parse committed revision!\n",
+			join("\n",@ci_output),"\n";
+	my ($rev_committed) = ($committed =~ /^Committed revision (\d+)\./);
+
+	# resync immediately
+	my @svn_up = (qw(svn up), "-r$svn_rev");
+	push @svn_up, '--ignore-externals' unless $_no_ignore_ext;
+	sys(@svn_up);
+	return fetch("$rev_committed=$commit")->{revision};
+}
+
+sub svn_log_xml {
+	my (@log_args) = @_;
+	my $log_fh = IO::File->new_tmpfile or croak $!;
+
+	my $pid = fork;
+	defined $pid or croak $!;
+
+	if ($pid == 0) {
+		open STDOUT, '>&', $log_fh or croak $!;
+		exec (qw(svn log --xml), @log_args) or croak $!
+	}
+
+	waitpid $pid, 0;
+	croak $? if $?;
+
+	seek $log_fh, 0, 0;
+	my @svn_log;
+	my $log = XML::Simple::XMLin( $log_fh,
+				ForceArray => ['path','revision','logentry'],
+				KeepRoot => 0,
+				KeyAttr => {	logentry => '+revision',
+						paths => '+path' },
+			)->{logentry};
+	foreach my $r (sort {$a <=> $b} keys %$log) {
+		my $log_msg = $log->{$r};
+		my ($Y,$m,$d,$H,$M,$S) = ($log_msg->{date} =~
+					/(\d{4})\-(\d\d)\-(\d\d)T
+					 (\d\d)\:(\d\d)\:(\d\d)\.\d+Z$/x)
+					 or croak "Failed to parse date: ",
+						 $log->{$r}->{date};
+		$log_msg->{date} = "+0000 $Y-$m-$d $H:$M:$S";
+
+		# XML::Simple can't handle <msg></msg> as a string:
+		if (ref $log_msg->{msg} eq 'HASH') {
+			$log_msg->{msg} = "\n";
+		} else {
+			$log_msg->{msg} .= "\n";
+		}
+		push @svn_log, $log->{$r};
+	}
+	return \@svn_log;
+}
+
+sub svn_log_raw {
+	my (@log_args) = @_;
+	my $pid = open my $log_fh,'-|';
+	defined $pid or croak $!;
+
+	if ($pid == 0) {
+		exec (qw(svn log), @log_args) or croak $!
+	}
+
+	my @svn_log;
+	my $state;
+	while (<$log_fh>) {
+		chomp;
+		if (/^\-{72}$/) {
+			$state = 'rev';
+
+			# if we have an empty log message, put something there:
+			if (@svn_log) {
+				$svn_log[0]->{msg} ||= "\n";
+			}
+			next;
+		}
+		if ($state eq 'rev' && s/^r(\d+)\s*\|\s*//) {
+			my $rev = $1;
+			my ($author, $date) = split(/\s*\|\s*/, $_, 2);
+			my ($Y,$m,$d,$H,$M,$S,$tz) = ($date =~
+					/(\d{4})\-(\d\d)\-(\d\d)\s
+					 (\d\d)\:(\d\d)\:(\d\d)\s([\-\+]\d+)/x)
+					 or croak "Failed to parse date: $date\n";
+			my %log_msg = (	revision => $rev,
+					date => "$tz $Y-$m-$d $H:$M:$S",
+					author => $author,
+					msg => '' );
+			unshift @svn_log, \%log_msg;
+			$state = 'msg_start';
+			next;
+		}
+		# skip the first blank line of the message:
+		if ($state eq 'msg_start' && /^$/) {
+			$state = 'msg';
+		} elsif ($state eq 'msg') {
+			$svn_log[0]->{msg} .= $_."\n";
+		}
+	}
+	close $log_fh or croak $?;
+	return \@svn_log;
+}
+
+sub svn_info {
+	my $url = shift || $SVN_URL;
+
+	my $pid = open my $info_fh, '-|';
+	defined $pid or croak $!;
+
+	if ($pid == 0) {
+		exec(qw(svn info),$url) or croak $!;
+	}
+
+	my $ret = {};
+	# only single-lines seem to exist in svn info output
+	while (<$info_fh>) {
+		chomp $_;
+		if (m#^([^:]+)\s*:\s*(\S*)$#) {
+			$ret->{$1} = $2;
+			push @{$ret->{-order}}, $1;
+		}
+	}
+	close $info_fh or croak $!;
+	return $ret;
+}
+
+sub sys { system(@_) == 0 or croak $? }
+
+sub git_addremove {
+	system(	"git-ls-files -z --others ".
+			"'--exclude-from=$GIT_DIR/$GIT_SVN/info/exclude'".
+				"| git-update-index --add -z --stdin; ".
+		"git-ls-files -z --deleted ".
+				"| git-update-index --remove -z --stdin; ".
+		"git-ls-files -z --modified".
+				"| git-update-index -z --stdin") == 0 or croak $?
+}
+
+sub s_to_file {
+	my ($str, $file, $mode) = @_;
+	open my $fd,'>',$file or croak $!;
+	print $fd $str,"\n" or croak $!;
+	close $fd or croak $!;
+	chmod ($mode &~ umask, $file) if (defined $mode);
+}
+
+sub file_to_s {
+	my $file = shift;
+	open my $fd,'<',$file or croak "$!: file: $file\n";
+	local $/;
+	my $ret = <$fd>;
+	close $fd or croak $!;
+	$ret =~ s/\s*$//s;
+	return $ret;
+}
+
+sub assert_revision_unknown {
+	my $revno = shift;
+	if (-f "$REV_DIR/$revno") {
+		croak "$REV_DIR/$revno already exists! ",
+				"Why are we refetching it?";
+	}
+}
+
+sub assert_revision_eq_or_unknown {
+	my ($revno, $commit) = @_;
+	if (-f "$REV_DIR/$revno") {
+		my $current = file_to_s("$REV_DIR/$revno");
+		if ($commit ne $current) {
+			croak "$REV_DIR/$revno already exists!\n",
+				"current: $current\nexpected: $commit\n";
+		}
+		return;
+	}
+}
+
+sub git_commit {
+	my ($log_msg, @parents) = @_;
+	assert_revision_unknown($log_msg->{revision});
+	my $out_fh = IO::File->new_tmpfile or croak $!;
+	my $info = svn_info('.');
+	my $uuid = $info->{'Repository UUID'};
+	defined $uuid or croak "Unable to get Repository UUID\n";
+
+	# commit parents can be conditionally bound to a particular
+	# svn revision via: "svn_revno=commit_sha1", filter them out here:
+	my @exec_parents;
+	foreach my $p (@parents) {
+		next unless defined $p;
+		if ($p =~ /^(\d+)=($sha1_short)$/o) {
+			if ($1 == $log_msg->{revision}) {
+				push @exec_parents, $2;
+			}
+		} else {
+			push @exec_parents, $p if $p =~ /$sha1_short/o;
+		}
+	}
+
+	my $pid = fork;
+	defined $pid or croak $!;
+	if ($pid == 0) {
+		$ENV{GIT_INDEX_FILE} = $GIT_SVN_INDEX;
+		git_addremove();
+		chomp(my $tree = `git-write-tree`);
+		croak if $?;
+		my $msg_fh = IO::File->new_tmpfile or croak $!;
+		print $msg_fh $log_msg->{msg}, "\ngit-svn-id: ",
+					"$SVN_URL\@$log_msg->{revision}",
+					" $uuid\n" or croak $!;
+		$msg_fh->flush == 0 or croak $!;
+		seek $msg_fh, 0, 0 or croak $!;
+
+		$ENV{GIT_AUTHOR_NAME} = $ENV{GIT_COMMITTER_NAME} =
+						$log_msg->{author};
+		$ENV{GIT_AUTHOR_EMAIL} = $ENV{GIT_COMMITTER_EMAIL} =
+						$log_msg->{author}."\@$uuid";
+		$ENV{GIT_AUTHOR_DATE} = $ENV{GIT_COMMITTER_DATE} =
+						$log_msg->{date};
+		my @exec = ('git-commit-tree',$tree);
+		push @exec, '-p', $_  foreach @exec_parents;
+		open STDIN, '<&', $msg_fh or croak $!;
+		open STDOUT, '>&', $out_fh or croak $!;
+		exec @exec or croak $!;
+	}
+	waitpid($pid,0);
+	croak if $?;
+
+	$out_fh->flush == 0 or croak $!;
+	seek $out_fh, 0, 0 or croak $!;
+	chomp(my $commit = do { local $/; <$out_fh> });
+	if ($commit !~ /^$sha1$/o) {
+		croak "Failed to commit, invalid sha1: $commit\n";
+	}
+	my @update_ref = ('git-update-ref',"refs/heads/$GIT_SVN-HEAD",$commit);
+	if (my $primary_parent = shift @exec_parents) {
+		push @update_ref, $primary_parent;
+	}
+	sys(@update_ref);
+	sys('git-update-ref',"$GIT_SVN/revs/$log_msg->{revision}",$commit);
+	print "r$log_msg->{revision} = $commit\n";
+	return $commit;
+}
+
+sub blob_to_symlink {
+	my ($blob, $link) = @_;
+	defined $link or croak "\$link not defined!\n";
+	croak "Not a sha1: $blob\n" unless $blob =~ /^$sha1$/o;
+	my $dest = `git-cat-file blob $blob`; # no newline, so no chomp
+	symlink $dest, $link or croak $!;
+}
+
+sub blob_to_file {
+	my ($blob, $file) = @_;
+	defined $file or croak "\$file not defined!\n";
+	croak "Not a sha1: $blob\n" unless $blob =~ /^$sha1$/o;
+	open my $blob_fh, '>', $file or croak "$!: $file\n";
+	my $pid = fork;
+	defined $pid or croak $!;
+
+	if ($pid == 0) {
+		open STDOUT, '>&', $blob_fh or croak $!;
+		exec('git-cat-file','blob',$blob);
+	}
+	waitpid $pid, 0;
+	croak $? if $?;
+
+	close $blob_fh or croak $!;
+}
+
+sub safe_qx {
+	my $pid = open my $child, '-|';
+	defined $pid or croak $!;
+	if ($pid == 0) {
+		exec(@_) or croak $?;
+	}
+	my @ret = (<$child>);
+	close $child or croak $?;
+	die $? if $?; # just in case close didn't error out
+	return wantarray ? @ret : join('',@ret);
+}
+
+sub svn_check_ignore_externals {
+	return if $_no_ignore_ext;
+	unless (grep /ignore-externals/,(safe_qx(qw(svn co -h)))) {
+		print STDERR "W: Installed svn version does not support ",
+				"--ignore-externals\n";
+		$_no_ignore_ext = 1;
+	}
+}
+__END__
+
+Data structures:
+
+@svn_log = array of log_msg hashes
+
+$log_msg hash
+{
+	msg => 'whitespace-formatted log entry
+',						# trailing newline is preserved
+	revision => '8',			# integer
+	date => '2004-02-24T17:01:44.108345Z',	# commit date
+	author => 'committer name'
+};
+
+
+@mods = array of diff-index line hashes, each element represents one line
+	of diff-index output
+
+diff-index line ($m hash)
+{
+	mode_a => first column of diff-index output, no leading ':',
+	mode_b => second column of diff-index output,
+	sha1_b => sha1sum of the final blob,
+	chg => change type [MCRAD],
+	file_a => original file name of a file (iff chg is 'C' or 'R')
+	file_b => new/current file name of a file (any chg)
+}
+;
diff --git a/contrib/git-svn/git-svn.txt b/contrib/git-svn/git-svn.txt
new file mode 100644
index 000000000..4b79fb0be
--- /dev/null
+++ b/contrib/git-svn/git-svn.txt
@@ -0,0 +1,208 @@
+git-svn(1)
+==========
+
+NAME
+----
+git-svn - bidirectional operation between a single Subversion branch and git
+
+SYNOPSIS
+--------
+'git-svn' <command> [options] [arguments]
+
+DESCRIPTION
+-----------
+git-svn is a simple conduit for changesets between a single Subversion
+branch and git.
+
+git-svn is not to be confused with git-svnimport.  The were designed
+with very different goals in mind.
+
+git-svn is designed for an individual developer who wants a
+bidirectional flow of changesets between a single branch in Subversion
+and an arbitrary number of branches in git.  git-svnimport is designed
+for read-only operation on repositories that match a particular layout
+(albeit the recommended one by SVN developers).
+
+For importing svn, git-svnimport is potentially more powerful when
+operating on repositories organized under the recommended
+trunk/branch/tags structure, and should be faster, too.
+
+git-svn completely ignores the very limited view of branching that
+Subversion has.  This allows git-svn to be much easier to use,
+especially on repositories that are not organized in a manner that
+git-svnimport is designed for.
+
+COMMANDS
+--------
+init::
+	Creates an empty git repository with additional metadata
+	directories for git-svn.  The SVN_URL must be specified
+	at this point.
+
+fetch::
+	Fetch unfetched revisions from the SVN_URL we are tracking.
+	refs/heads/git-svn-HEAD will be updated to the latest revision.
+
+commit::
+	Commit specified commit or tree objects to SVN.  This relies on
+	your imported fetch data being up-to-date.  This makes
+	absolutely no attempts to do patching when committing to SVN, it
+	simply overwrites files with those specified in the tree or
+	commit.  All merging is assumed to have taken place
+	independently of git-svn functions.
+
+rebuild::
+	Not a part of daily usage, but this is a useful command if
+	you've just cloned a repository (using git-clone) that was
+	tracked with git-svn.  Unfortunately, git-clone does not clone
+	git-svn metadata and the svn working tree that git-svn uses for
+	its operations.  This rebuilds the metadata so git-svn can
+	resume fetch operations.  SVN_URL may be optionally specified if
+	the directory/repository you're tracking has moved or changed
+	protocols.
+
+OPTIONS
+-------
+-r <ARG>::
+--revision <ARG>::
+	Only used with the 'fetch' command.
+
+	Takes any valid -r<argument> svn would accept and passes it
+	directly to svn. -r<ARG1>:<ARG2> ranges and "{" DATE "}" syntax
+	is also supported.  This is passed directly to svn, see svn
+	documentation for more details.
+
+	This can allow you to make partial mirrors when running fetch.
+
+-::
+--stdin::
+	Only used with the 'commit' command.
+
+	Read a list of commits from stdin and commit them in reverse
+	order.  Only the leading sha1 is read from each line, so
+	git-rev-list --pretty=oneline output can be used.
+
+--rmdir::
+	Only used with the 'commit' command.
+
+	Remove directories from the SVN tree if there are no files left
+	behind.  SVN can version empty directories, and they are not
+	removed by default if there are no files left in them.  git
+	cannot version empty directories.  Enabling this flag will make
+	the commit to SVN act like git.
+
+-e::
+--edit::
+	Only used with the 'commit' command.
+
+	Edit the commit message before committing to SVN.  This is off by
+	default for objects that are commits, and forced on when committing
+	tree objects.
+
+COMPATIBILITY OPTIONS
+---------------------
+--no-ignore-externals::
+	Only used with the 'fetch' and 'rebuild' command.
+
+	By default, git-svn passes --ignore-externals to svn to avoid
+	fetching svn:external trees into git.  Pass this flag to enable
+	externals tracking directly via git.
+
+	Versions of svn that do not support --ignore-externals are
+	automatically detected and this flag will be automatically
+	enabled for them.
+
+	Otherwise, do not enable this flag unless you know what you're
+	doing.
+
+--no-stop-on-copy::
+	Only used with the 'fetch' command.
+
+	By default, git-svn passes --stop-on-copy to avoid dealing with
+	the copied/renamed branch directory problem entirely.  A
+	copied/renamed branch is the result of a <SVN_URL> being created
+	in the past from a different source.  These are problematic to
+	deal with even when working purely with svn if you work inside
+	subdirectories.
+
+	Do not use this flag unless you know exactly what you're getting
+	yourself into.  You have been warned.
+
+Examples
+~~~~~~~~
+
+Tracking and contributing to an Subversion managed-project:
+
+# Initialize a tree (like git init-db)::
+	git-svn init http://svn.foo.org/project/trunk
+# Fetch remote revisions::
+	git-svn fetch
+# Create your own branch to hack on::
+	git checkout -b my-branch git-svn-HEAD
+# Commit only the git commits you want to SVN::
+	git-svn commit <tree-ish> [<tree-ish_2> ...]
+# Commit all the git commits from my-branch that don't exist in SVN::
+	git rev-list --pretty=oneline git-svn-HEAD..my-branch | git-svn commit
+# Something is committed to SVN, pull the latest into your branch::
+	git-svn fetch && git pull . git-svn-HEAD
+
+DESIGN PHILOSOPHY
+-----------------
+Merge tracking in Subversion is lacking and doing branched development
+with Subversion is cumbersome as a result.  git-svn completely forgoes
+any automated merge/branch tracking on the Subversion side and leaves it
+entirely up to the user on the git side.  It's simply not worth it to do
+a useful translation when the the original signal is weak.
+
+TRACKING MULTIPLE REPOSITORIES OR BRANCHES
+------------------------------------------
+This is for advanced users, most users should ignore this section.
+
+Because git-svn does not care about relationships between different
+branches or directories in a Subversion repository, git-svn has a simple
+hack to allow it to track an arbitrary number of related _or_ unrelated
+SVN repositories via one git repository.  Simply set the GIT_SVN_ID
+environment variable to a name other other than "git-svn" (the default)
+and git-svn will ignore the contents of the $GIT_DIR/git-svn directory
+and instead do all of its work in $GIT_DIR/$GIT_SVN_ID for that
+invocation.
+
+ADDITIONAL FETCH ARGUMENTS
+--------------------------
+This is for advanced users, most users should ignore this section.
+
+Unfetched SVN revisions may be imported as children of existing commits
+by specifying additional arguments to 'fetch'.  Additional parents may
+optionally be specified in the form of sha1 hex sums at the
+command-line.  Unfetched SVN revisions may also be tied to particular
+git commits with the following syntax:
+
+	svn_revision_number=git_commit_sha1
+
+This allows you to tie unfetched SVN revision 375 to your current HEAD::
+
+	git-svn fetch 375=$(git-rev-parse HEAD)
+
+BUGS
+----
+If somebody commits a conflicting changeset to SVN at a bad moment
+(right before you commit) causing a conflict and your commit to fail,
+your svn working tree ($GIT_DIR/git-svn/tree) may be dirtied.  The
+easiest thing to do is probably just to rm -rf $GIT_DIR/git-svn/tree and
+run 'rebuild'.
+
+We ignore all SVN properties except svn:executable.  Too difficult to
+map them since we rely heavily on git write-tree being _exactly_ the
+same on both the SVN and git working trees and I prefer not to clutter
+working trees with metadata files.
+
+svn:keywords can't be ignored in Subversion (at least I don't know of
+a way to ignore them).
+
+Author
+------
+Written by Eric Wong <normalperson@yhbt.net>.
+
+Documentation
+-------------
+Written by Eric Wong <normalperson@yhbt.net>.