git-svn: New flag to emulate empty directories

rchyena · Eric Wong · commit 40a1530c07a6 · 2011-09-01T07:10:22.000Z
Adds a --preserve-empty-dirs flag to the clone operation that will detect
empty directories in the remote Subversion repository and create placeholder
files in the corresponding local Git directories.  This allows "empty"
directories to exist in the history of a Git repository.

Also adds the --placeholder-file flag to control the name of any placeholder
files created.  Default value is ".gitignore".

Signed-off-by: Ray Chen &lt;rchen@cs.umd.edu&gt;
Acked-by: Eric Wong &lt;normalperson@yhbt.net&gt;
diff --git a/Documentation/git-svn.txt b/Documentation/git-svn.txt
@@ -157,6 +157,17 @@ Skip "branches" and "tags" of first level directories;;
 	affecting the working tree; and the 'rebase' command will be
 	able to update the working tree with the latest changes.
 
+--preserve-empty-dirs;;
+	Create a placeholder file in the local Git repository for each
+	empty directory fetched from Subversion.  This includes directories
+	that become empty by removing all entries in the Subversion
+	repository (but not the directory itself).  The placeholder files
+	are also tracked and removed when no longer necessary.
+
+--placeholder-filename=<filename>;;
+	Set the name of placeholder files created by --preserve-empty-dirs.
+	Default: ".gitignore"
+
 'rebase'::
 	This fetches revisions from the SVN parent of the current HEAD
 	and rebases the current (uncommitted to SVN) work against it.
diff --git a/git-svn.perl b/git-svn.perl
@@ -89,6 +89,7 @@ BEGIN
 	$_prefix, $_no_checkout, $_url, $_verbose,
 	$_git_format, $_commit_url, $_tag, $_merge_info);
 $Git::SVN::_follow_parent = 1;
+$SVN::Git::Fetcher::_placeholder_filename = ".gitignore";
 $_q ||= 0;
 my %remote_opts = ( 'username=s' => \$Git::SVN::Prompt::_username,
                     'config-dir=s' => \$Git::SVN::Ra::config_dir,
@@ -139,6 +140,10 @@ BEGIN
 			   %fc_opts } ],
 	clone => [ \&cmd_clone, "Initialize and fetch revisions",
 			{ 'revision|r=s' => \$_revision,
+			  'preserve-empty-dirs' =>
+				\$SVN::Git::Fetcher::_preserve_empty_dirs,
+			  'placeholder-filename=s' =>
+				\$SVN::Git::Fetcher::_placeholder_filename,
 			   %fc_opts, %init_opts } ],
 	init => [ \&cmd_init, "Initialize a repo for tracking" .
 			  " (requires URL argument)",
@@ -386,6 +391,12 @@ sub do_git_init_db {
 	my $ignore_regex = \$SVN::Git::Fetcher::_ignore_regex;
 	command_noisy('config', "$pfx.ignore-paths", $$ignore_regex)
 		if defined $$ignore_regex;
+
+	if (defined $SVN::Git::Fetcher::_preserve_empty_dirs) {
+		my $fname = \$SVN::Git::Fetcher::_placeholder_filename;
+		command_noisy('config', "$pfx.preserve-empty-dirs", 'true');
+		command_noisy('config', "$pfx.placeholder-filename", $$fname);
+	}
 }
 
 sub init_subdir {
@@ -4080,12 +4091,13 @@ sub _read_password {
 }
 
 package SVN::Git::Fetcher;
-use vars qw/@ISA/;
+use vars qw/@ISA $_ignore_regex $_preserve_empty_dirs $_placeholder_filename
+            @deleted_gpath %added_placeholder $repo_id/;
 use strict;
 use warnings;
 use Carp qw/croak/;
+use File::Basename qw/dirname/;
 use IO::File qw//;
-use vars qw/$_ignore_regex/;
 
 # file baton members: path, mode_a, mode_b, pool, fh, blob, base
 sub new {
@@ -4097,8 +4109,34 @@ sub new {
 		$self->{empty_symlinks} =
 		                  _mark_empty_symlinks($git_svn, $switch_path);
 	}
-	$self->{ignore_regex} = eval { command_oneline('config', '--get',
-			     "svn-remote.$git_svn->{repo_id}.ignore-paths") };
+
+	# 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} = {};
@@ -4227,6 +4265,8 @@ sub delete_entry {
 		$self->{gii}->remove($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;
 }
@@ -4259,7 +4299,15 @@ sub add_file {
 		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' };
 }
@@ -4277,13 +4325,21 @@ sub add_directory {
 			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 };
 }
@@ -4447,12 +4503,96 @@ sub 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, $_);
+	}
+}
+
 package SVN::Git::Editor;
 use vars qw/@ISA $_rmdir $_cp_similarity $_find_copies_harder $_rename_limit/;
 use strict;
diff --git a/t/t9160-git-svn-preserve-empty-dirs.sh b/t/t9160-git-svn-preserve-empty-dirs.sh
