URL: null
spec: ftp://ftp.foo.com/dir1/entry.txt
expected: ftp://ftp.foo.com/dir1/entry.txt

URL: null
spec: ftp://br:pwd@ftp.foo.com/dir1/jar.jar
expected: ftp://br:pwd@ftp.foo.com/dir1/jar.jar

URL: ftp://ftp.foo.com/dir1/foo.txt
spec: bar.txt
expected: ftp://ftp.foo.com/dir1/bar.txt

URL: ftp://ftp.foo.com/dir1/jar.jar
spec: /entry.txt
expected: ftp://ftp.foo.com/entry.txt

URL: ftp://ftp.foo.com/dir1/jar.jar
spec: dir1/entry.txt
expected: ftp://ftp.foo.com/dir1/dir1/entry.txt

URL: ftp://ftp.foo.com/dir1/jar.jar
spec: /dir1/entry.txt
expected: ftp://ftp.foo.com/dir1/entry.txt

URL: ftp://br:pwd@ftp.foo.com/dir1/jar.jar
spec: /dir1/entry.txt
expected: ftp://br:pwd@ftp.foo.com/dir1/entry.txt