git-svn: add join_paths() to safely concatenate paths

Otherwise you might wind up with things like...

    my $path1 = undef;
    my $path2 = 'foo';
    my $path = $path1 . '/' . $path2;

creating '/foo'.  Or this...

    my $path1 = 'foo/';
    my $path2 = 'bar';
    my $path = $path1 . '/' . $path2;

creating 'foo//bar'.

Could have used File::Spec, but I'm shying away from it due to SVN
1.7's pickiness about paths.  Felt it would be better to have our own
we can control completely.

[ew: commit title]

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

4 files changed, 72 insertions, 5 deletions

diff --git a/git-svn.perl b/git-svn.perl
index a857484c58..6e3e240473 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -34,6 +34,7 @@ use Git::SVN::Utils qw(
 	can_compress
 	canonicalize_path
 	canonicalize_url
+	join_paths
 );
 
 use Git qw(
@@ -1275,7 +1276,7 @@ sub get_svnprops {
 	$path = $cmd_dir_prefix . $path;
 	fatal("No such file or directory: $path") unless -e $path;
 	my $is_dir = -d $path ? 1 : 0;
-	$path = $gs->{path} . '/' . $path;
+	$path = join_paths($gs->{path}, $path);
 
 	# canonicalize the path (otherwise libsvn will abort or fail to
 	# find the file)
diff --git a/perl/Git/SVN.pm b/perl/Git/SVN.pm
index fc1ac07136..ff747821fb 100644
--- a/perl/Git/SVN.pm
+++ b/perl/Git/SVN.pm
@@ -23,7 +23,11 @@ use Git qw(
     command_output_pipe
     command_close_pipe
 );
-use Git::SVN::Utils qw(fatal can_compress);
+use Git::SVN::Utils qw(
+	fatal
+	can_compress
+	join_paths
+);
 
 my $can_use_yaml;
 BEGIN {
@@ -316,9 +320,7 @@ sub init_remote_config {
 			}
 			my $old_path = $self->path;
 			$url =~ s!^\Q$min_url\E(/|$)!!;
-			if (length $old_path) {
-				$url .= "/$old_path";
-			}
+			$url = join_paths($url, $old_path);
 			$self->path($url);
 			$url = $min_url;
 		}
diff --git a/perl/Git/SVN/Utils.pm b/perl/Git/SVN/Utils.pm
index 4925410dd1..4005da9d7d 100644
--- a/perl/Git/SVN/Utils.pm
+++ b/perl/Git/SVN/Utils.pm
@@ -12,6 +12,7 @@ our @EXPORT_OK = qw(
 	can_compress
 	canonicalize_path
 	canonicalize_url
+	join_paths
 );
 
 
@@ -134,4 +135,35 @@ sub _canonicalize_url_ourselves {
 }
 
 
+=head3 join_paths
+
+    my $new_path = join_paths(@paths);
+
+Appends @paths together into a single path.  Any empty paths are ignored.
+
+=cut
+
+sub join_paths {
+	my @paths = @_;
+
+	@paths = grep { defined $_ && length $_ } @paths;
+
+	return '' unless @paths;
+	return $paths[0] if @paths == 1;
+
+	my $new_path = shift @paths;
+	$new_path =~ s{/+$}{};
+
+	my $last_path = pop @paths;
+	$last_path =~ s{^/+}{};
+
+	for my $path (@paths) {
+		$path =~ s{^/+}{};
+		$path =~ s{/+$}{};
+		$new_path .= "/$path";
+	}
+
+	return $new_path .= "/$last_path";
+}
+
 1;
diff --git a/t/Git-SVN/Utils/join_paths.t b/t/Git-SVN/Utils/join_paths.t
new file mode 100644
index 0000000000..d4488e7162
--- /dev/null
+++ b/t/Git-SVN/Utils/join_paths.t
@@ -0,0 +1,32 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use Test::More 'no_plan';
+
+use Git::SVN::Utils qw(
+	join_paths
+);
+
+# A reference cannot be a hash key, so we use an array.
+my @tests = (
+	[]					=> '',
+	["/x.com", "bar"]			=> '/x.com/bar',
+	["x.com", ""]				=> 'x.com',
+	["/x.com/foo/", undef, "bar"]		=> '/x.com/foo/bar',
+	["x.com/foo/", "/bar/baz/"]		=> 'x.com/foo/bar/baz/',
+	["foo", "bar"]				=> 'foo/bar',
+	["/foo/bar", "baz", "/biff"]		=> '/foo/bar/baz/biff',
+	["", undef, "."]			=> '.',
+	[]					=> '',
+
+);
+
+while(@tests) {
+	my($have, $want) = splice @tests, 0, 2;
+
+	my $args = join ", ", map { qq['$_'] } map { defined($_) ? $_ : 'undef' } @$have;
+	my $name = "join_paths($args) eq '$want'";
+	is join_paths(@$have), $want, $name;
+}