perl/Git/SVN/Fetcher.pm

package Git::SVN::Fetcher;
use vars qw/@ISA $_ignore_regex $_preserve_empty_dirs $_placeholder_filename
            @deleted_gpath %added_placeholder $repo_id/;
use strict;
use warnings;
use SVN::Delta;
use Carp qw/croak/;
use File::Basename qw/dirname/;
use IO::File qw//;
use Git qw/command command_oneline command_noisy command_output_pipe
           command_input_pipe command_close_pipe
           command_bidi_pipe command_close_bidi_pipe/;
BEGIN {
	@ISA = qw(SVN::Delta::Editor);
}

# file baton members: path, mode_a, mode_b, pool, fh, blob, base
sub new {
	my ($class, $git_svn, $switch_path) = @_;
	my $self = SVN::Delta::Editor->new;
	bless $self, $class;
	if (exists $git_svn->{last_commit}) {
		$self->{c} = $git_svn->{last_commit};
		$self->{empty_symlinks} =
		                  _mark_empty_symlinks($git_svn, $switch_path);
	}

	# some options are read globally, but can be overridden locally
	# per [svn-remote "..."] section.  Command-line options will *NOT*
	# override options set in an [svn-remote "..."] section
	$repo_id = $git_svn->{repo_id};
	my $k = "svn-remote.$repo_id.ignore-paths";
	my $v = eval { command_oneline('config', '--get', $k) };
	$self->{ignore_regex} = $v;

	$k = "svn-remote.$repo_id.preserve-empty-dirs";
	$v = eval { command_oneline('config', '--get', '--bool', $k) };
	if ($v && $v eq 'true') {
		$_preserve_empty_dirs = 1;
		$k = "svn-remote.$repo_id.placeholder-filename";
		$v = eval { command_oneline('config', '--get', $k) };
		$_placeholder_filename = $v;
	}

	# Load the list of placeholder files added during previous invocations.
	$k = "svn-remote.$repo_id.added-placeholder";
	$v = eval { command_oneline('config', '--get-all', $k) };
	if ($_preserve_empty_dirs && $v) {
		# command() prints errors to stderr, so we only call it if
		# command_oneline() succeeded.
		my @v = command('config', '--get-all', $k);
		$added_placeholder{ dirname($_) } = $_ foreach @v;
	}

	$self->{empty} = {};
	$self->{dir_prop} = {};
	$self->{file_prop} = {};
	$self->{absent_dir} = {};
	$self->{absent_file} = {};
	require Git::IndexInfo;
	$self->{gii} = $git_svn->tmp_index_do(sub { Git::IndexInfo->new });
	$self->{pathnameencoding} = Git::config('svn.pathnameencoding');
	$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, $switch_path) = @_;
	my $bool = Git::config_bool('svn.brokenSymlinkWorkaround');
	return {} if (!defined($bool)) || (defined($bool) && ! $bool);

	my %ret;
	my ($rev, $cmt) = $git_svn->last_rev_commit;
	return {} unless ($rev && $cmt);

	# allow the warning to be printed for each revision we fetch to
	# ensure the user sees it.  The user can also disable the workaround
	# on the repository even while git svn is running and the next
	# revision fetched will skip this expensive function.
	my $printed_warning;
	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 $pfx = defined($switch_path) ? $switch_path : $git_svn->path;
	$pfx .= '/' if length($pfx);
	while (<$ls>) {
		chomp;
		s/\A100644 blob $empty_blob\t//o or next;
		unless ($printed_warning) {
			print STDERR "Scanning for empty symlinks, ",
			             "this may take a while if you have ",
				     "many empty files\n",
				     "You may disable this with `",
				     "git config svn.brokenSymlinkWorkaround ",
				     "false'.\n",
				     "This may be done in a different ",
				     "terminal without restarting ",
				     "git svn\n";
			$printed_warning = 1;
		}
		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;
}

# returns true if a given path is inside a ".git" directory
sub in_dot_git {
	$_[0] =~ m{(?:^|/)\.git(?:/|$)};
}

# return value: 0 -- don't ignore, 1 -- ignore
sub is_path_ignored {
	my ($self, $path) = @_;
	return 1 if in_dot_git($path);
	return 1 if defined($self->{ignore_regex}) &&
	            $path =~ m!$self->{ignore_regex}!;
	return 0 unless defined($_ignore_regex);
	return 1 if $path =~ m!$_ignore_regex!o;
	return 0;
}

sub set_path_strip {
	my ($self, $path) = @_;
	$self->{path_strip} = qr/^\Q$path\E(\/|$)/ if length $path;
}

sub open_root {
	{ path => '' };
}

sub open_directory {
	my ($self, $path, $pb, $rev) = @_;
	{ path => $path };
}

sub git_path {
	my ($self, $path) = @_;
	if (my $enc = $self->{pathnameencoding}) {
		require Encode;
		Encode::from_to($path, 'UTF-8', $enc);
	}
	if ($self->{path_strip}) {
		$path =~ s!$self->{path_strip}!! or
		  die "Failed to strip path '$path' ($self->{path_strip})\n";
	}
	$path;
}

sub delete_entry {
	my ($self, $path, $rev, $pb) = @_;
	return undef if $self->is_path_ignored($path);

	my $gpath = $self->git_path($path);
	return undef if ($gpath eq '');

	# remove entire directories.
	my ($tree) = (command('ls-tree', '-z', $self->{c}, "./$gpath")
	                 =~ /\A040000 tree ([a-f\d]{40})\t\Q$gpath\E\0/);
	if ($tree) {
		my ($ls, $ctx) = command_output_pipe(qw/ls-tree
		                                     -r --name-only -z/,
				                     $tree);
		local $/ = "\0";
		while (<$ls>) {
			chomp;
			my $rmpath = "$gpath/$_";
			$self->{gii}->remove($rmpath);
			print "\tD\t$rmpath\n" unless $::_q;
		}
		print "\tD\t$gpath/\n" unless $::_q;
		command_close_pipe($ls, $ctx);
	} else {
		$self->{gii}->remove($gpath);
		print "\tD\t$gpath\n" unless $::_q;
	}
	# Don't add to @deleted_gpath if we're deleting a placeholder file.
	push @deleted_gpath, $gpath unless $added_placeholder{dirname($path)};
	$self->{empty}->{$path} = 0;
	undef;
}

sub open_file {
	my ($self, $path, $pb, $rev) = @_;
	my ($mode, $blob);

	goto out if $self->is_path_ignored($path);

	my $gpath = $self->git_path($path);
	($mode, $blob) = (command('ls-tree', '-z', $self->{c}, "./$gpath")
	                     =~ /\A(\d{6}) blob ([a-f\d]{40})\t\Q$gpath\E\0/);
	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';
	}
out:
	{ path => $path, mode_a => $mode, mode_b => $mode, blob => $blob,
	  pool => SVN::Pool->new, action => 'M' };
}

sub add_file {
	my ($self, $path, $pb, $cp_path, $cp_rev) = @_;
	my $mode;

	if (!$self->is_path_ignored($path)) {
		my ($dir, $file) = ($path =~ m#^(.*?)/?([^/]+)$#);
		delete $self->{empty}->{$dir};
		$mode = '100644';

		if ($added_placeholder{$dir}) {
			# Remove our placeholder file, if we created one.
			delete_entry($self, $added_placeholder{$dir})
				unless $path eq $added_placeholder{$dir};
			delete $added_placeholder{$dir}
		}
	}

	{ path => $path, mode_a => $mode, mode_b => $mode,
	  pool => SVN::Pool->new, action => 'A' };
}

sub add_directory {
	my ($self, $path, $cp_path, $cp_rev) = @_;
	goto out if $self->is_path_ignored($path);
	my $gpath = $self->git_path($path);
	if ($gpath eq '') {
		my ($ls, $ctx) = command_output_pipe(qw/ls-tree
		                                     -r --name-only -z/,
				                     $self->{c});
		local $/ = "\0";
		while (<$ls>) {
			chomp;
			$self->{gii}->remove($_);
			print "\tD\t$_\n" unless $::_q;
			push @deleted_gpath, $gpath;
		}
		command_close_pipe($ls, $ctx);
		$self->{empty}->{$path} = 0;
	}
	my ($dir, $file) = ($path =~ m#^(.*?)/?([^/]+)$#);
	delete $self->{empty}->{$dir};
	$self->{empty}->{$path} = 1;

	if ($added_placeholder{$dir}) {
		# Remove our placeholder file, if we created one.
		delete_entry($self, $added_placeholder{$dir});
		delete $added_placeholder{$dir}
	}

out:
	{ path => $path };
}

sub change_dir_prop {
	my ($self, $db, $prop, $value) = @_;
	return undef if $self->is_path_ignored($db->{path});
	$self->{dir_prop}->{$db->{path}} ||= {};
	$self->{dir_prop}->{$db->{path}}->{$prop} = $value;
	undef;
}

sub absent_directory {
	my ($self, $path, $pb) = @_;
	return undef if $self->is_path_ignored($path);
	$self->{absent_dir}->{$pb->{path}} ||= [];
	push @{$self->{absent_dir}->{$pb->{path}}}, $path;
	undef;
}

sub absent_file {
	my ($self, $path, $pb) = @_;
	return undef if $self->is_path_ignored($path);
	$self->{absent_file}->{$pb->{path}} ||= [];
	push @{$self->{absent_file}->{$pb->{path}}}, $path;
	undef;
}

sub change_file_prop {
	my ($self, $fb, $prop, $value) = @_;
	return undef if $self->is_path_ignored($fb->{path});
	if ($prop eq 'svn:executable') {
		if ($fb->{mode_b} != 120000) {
			$fb->{mode_b} = defined $value ? 100755 : 100644;
		}
	} elsif ($prop eq 'svn:special') {
		$fb->{mode_b} = defined $value ? 120000 : 100644;
	} else {
		$self->{file_prop}->{$fb->{path}} ||= {};
		$self->{file_prop}->{$fb->{path}}->{$prop} = $value;
	}
	undef;
}

sub apply_textdelta {
	my ($self, $fb, $exp) = @_;
	return undef if $self->is_path_ignored($fb->{path});
	my $fh = $::_repository->temp_acquire('svn_delta');
	# $fh gets auto-closed() by SVN::TxDelta::apply(),
	# (but $base does not,) so dup() it for reading in close_file
	open my $dup, '<&', $fh or croak $!;
	my $base = $::_repository->temp_acquire('git_blob');

	if ($fb->{blob}) {
		my ($base_is_link, $size);

		if ($fb->{mode_a} eq '120000' &&
		    ! $self->{empty_symlinks}->{$fb->{path}}) {
			print $base 'link ' or die "print $!\n";
			$base_is_link = 1;
		}
	retry:
		$size = $::_repository->cat_blob($fb->{blob}, $base);
		die "Failed to read object $fb->{blob}" if ($size < 0);

		if (defined $exp) {
			seek $base, 0, 0 or croak $!;
			my $got = ::md5sum($base);
			if ($got ne $exp) {
				my $err = "Checksum mismatch: ".
				       "$fb->{path} $fb->{blob}\n" .
				       "expected: $exp\n" .
				       "     got: $got\n";
				if ($base_is_link) {
					warn $err,
					     "Retrying... (possibly ",
					     "a bad symlink from SVN)\n";
					$::_repository->temp_reset($base);
					$base_is_link = 0;
					goto retry;
				}
				die $err;
			}
		}
	}
	seek $base, 0, 0 or croak $!;
	$fb->{fh} = $fh;
	$fb->{base} = $base;
	[ SVN::TxDelta::apply($base, $dup, undef, $fb->{path}, $fb->{pool}) ];
}

sub close_file {
	my ($self, $fb, $exp) = @_;
	return undef if $self->is_path_ignored($fb->{path});

	my $hash;
	my $path = $self->git_path($fb->{path});
	if (my $fh = $fb->{fh}) {
		if (defined $exp) {
			seek($fh, 0, 0) or croak $!;
			my $got = ::md5sum($fh);
			if ($got ne $exp) {
				die "Checksum mismatch: $path\n",
				    "expected: $exp\n    got: $got\n";
			}
		}
		if ($fb->{mode_b} == 120000) {
			sysseek($fh, 0, 0) or croak $!;
			my $rd = sysread($fh, my $buf, 5);

			if (!defined $rd) {
				croak "sysread: $!\n";
			} elsif ($rd == 0) {
				warn "$path has mode 120000",
				     " 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');
				my $res;
				while ($res = sysread($fh, my $str, 1024)) {
					my $out = syswrite($tmp_fh, $str, $res);
					defined($out) && $out == $res
						or croak("write ",
							Git::temp_path($tmp_fh),
							": $!\n");
				}
				defined $res or croak $!;

				($fh, $tmp_fh) = ($tmp_fh, $fh);
				Git::temp_release($tmp_fh, 1);
			}
		}

		$hash = $::_repository->hash_and_insert_object(
				Git::temp_path($fh));
		$hash =~ /^[a-f\d]{40}$/ or die "not a sha1: $hash\n";

		Git::temp_release($fb->{base}, 1);
		Git::temp_release($fh, 1);
	} else {
		$hash = $fb->{blob} or die "no blob information\n";
	}
	$fb->{pool}->clear;
	$self->{gii}->update($fb->{mode_b}, $hash, $path) or croak $!;
	print "\t$fb->{action}\t$path\n" if $fb->{action} && ! $::_q;
	undef;
}

sub abort_edit {
	my $self = shift;
	$self->{nr} = $self->{gii}->{nr};
	delete $self->{gii};
	$self->SUPER::abort_edit(@_);
}

sub close_edit {
	my $self = shift;

	if ($_preserve_empty_dirs) {
		my @empty_dirs;

		# Any entry flagged as empty that also has an associated
		# dir_prop represents a newly created empty directory.
		foreach my $i (keys %{$self->{empty}}) {
			push @empty_dirs, $i if exists $self->{dir_prop}->{$i};
		}

		# Search for directories that have become empty due subsequent
		# file deletes.
		push @empty_dirs, $self->find_empty_directories();

		# Finally, add a placeholder file to each empty directory.
		$self->add_placeholder_file($_) foreach (@empty_dirs);

		$self->stash_placeholder_list();
	}

	$self->{git_commit_ok} = 1;
	$self->{nr} = $self->{gii}->{nr};
	delete $self->{gii};
	$self->SUPER::close_edit(@_);
}

sub find_empty_directories {
	my ($self) = @_;
	my @empty_dirs;
	my %dirs = map { dirname($_) => 1 } @deleted_gpath;

	foreach my $dir (sort keys %dirs) {
		next if $dir eq ".";

		# If there have been any additions to this directory, there is
		# no reason to check if it is empty.
		my $skip_added = 0;
		foreach my $t (qw/dir_prop file_prop/) {
			foreach my $path (keys %{ $self->{$t} }) {
				if (exists $self->{$t}->{dirname($path)}) {
					$skip_added = 1;
					last;
				}
			}
			last if $skip_added;
		}
		next if $skip_added;

		# Use `git ls-tree` to get the filenames of this directory
		# that existed prior to this particular commit.
		my $ls = command('ls-tree', '-z', '--name-only',
				 $self->{c}, "$dir/");
		my %files = map { $_ => 1 } split(/\0/, $ls);

		# Remove the filenames that were deleted during this commit.
		delete $files{$_} foreach (@deleted_gpath);

		# Report the directory if there are no filenames left.
		push @empty_dirs, $dir unless (scalar %files);
	}
	@empty_dirs;
}

sub add_placeholder_file {
	my ($self, $dir) = @_;
	my $path = "$dir/$_placeholder_filename";
	my $gpath = $self->git_path($path);

	my $fh = $::_repository->temp_acquire($gpath);
	my $hash = $::_repository->hash_and_insert_object(Git::temp_path($fh));
	Git::temp_release($fh, 1);
	$self->{gii}->update('100644', $hash, $gpath) or croak $!;

	# The directory should no longer be considered empty.
	delete $self->{empty}->{$dir} if exists $self->{empty}->{$dir};

	# Keep track of any placeholder files we create.
	$added_placeholder{$dir} = $path;
}

sub stash_placeholder_list {
	my ($self) = @_;
	my $k = "svn-remote.$repo_id.added-placeholder";
	my $v = eval { command_oneline('config', '--get-all', $k) };
	command_noisy('config', '--unset-all', $k) if $v;
	foreach (values %added_placeholder) {
		command_noisy('config', '--add', $k, $_);
	}
}

1;
__END__

Git::SVN::Fetcher - tree delta consumer for "git svn fetch"

=head1 SYNOPSIS

    use SVN::Core;
    use SVN::Ra;
    use Git::SVN;
    use Git::SVN::Fetcher;
    use Git;

    my $gs = Git::SVN->find_by_url($url);
    my $ra = SVN::Ra->new(url => $url);
    my $editor = Git::SVN::Fetcher->new($gs);
    my $reporter = $ra->do_update($SVN::Core::INVALID_REVNUM, '',
                                  1, $editor);
    $reporter->set_path('', $old_rev, 0);
    $reporter->finish_report;
    my $tree = $gs->tmp_index_do(sub { command_oneline('write-tree') });

    foreach my $path (keys %{$editor->{dir_prop}) {
        my $props = $editor->{dir_prop}{$path};
        foreach my $prop (keys %$props) {
            print "property $prop at $path changed to $props->{$prop}\n";
        }
    }
    foreach my $path (keys %{$editor->{empty}) {
        my $action = $editor->{empty}{$path} ? 'added' : 'removed';
        print "empty directory $path $action\n";
    }
    foreach my $path (keys %{$editor->{file_prop}) { ... }
    foreach my $parent (keys %{$editor->{absent_dir}}) {
        my @children = @{$editor->{abstent_dir}{$parent}};
        print "cannot fetch directory $parent/$_: not authorized?\n"
            foreach @children;
    }
    foreach my $parent (keys %{$editor->{absent_file}) { ... }

=head1 DESCRIPTION

This is a subclass of C<SVN::Delta::Editor>, which means it implements
callbacks to act as a consumer of Subversion tree deltas.  This
particular implementation of those callbacks is meant to store
information about the resulting content which B<git svn fetch> could
use to populate new commits and new entries for F<unhandled.log>.
More specifically:

=over

=item * Additions, removals, and modifications of files are propagated
to git-svn's index file F<$GIT_DIR/svn/$refname/index> using
B<git update-index>.

=item * Changes in Subversion path properties are recorded in the
C<dir_prop> and C<file_prop> fields (which are hashes).

=item * Addition and removal of empty directories are indicated by
entries with value 1 and 0 respectively in the C<empty> hash.

=item * Paths that are present but cannot be conveyed (presumably due
to permissions) are recorded in the C<absent_file> and
C<absent_dirs> hashes.  For each key, the corresponding value is
a list of paths under that directory that were present but
could not be conveyed.

=back

The interface is unstable.  Do not use this module unless you are
developing git-svn.

=head1 DEPENDENCIES

L<SVN::Delta> from the Subversion perl bindings,
the core L<Carp>, L<File::Basename>, and L<IO::File> modules,
and git's L<Git> helper module.

C<Git::SVN::Fetcher> has not been tested using callers other than
B<git-svn> itself.

=head1 SEE ALSO

L<SVN::Delta>,
L<Git::SVN::Editor>.

=head1 INCOMPATIBILITIES

None reported.

=head1 BUGS

None.