Add new config for PrettyPrinter to minimize empty tags

[ashawley]

This commit containing a unit test was mentioned last year in #46, and I thought the copy constructor using minimizeEmpty=true was broken, but it appears scala-xml does the right thing!

A new parameter to PrettyPrinter is added here for passing minimizeEmpty to the pretty-printed XML:

val pp = new xml.PrettyPrinter(80, 2, minimizeEmpty = true)
val x = <node><leaf></leaf></node>
pp.format(x))
// <node>
//   <leaf/>
// </node> 

[debanne]

Hello, when the option minimizeEmpty is set to true, is PretttyPrinter still transforming <a ... /> to <a>\n </a> when the line is longer than "width" or does it prevent this behaviour?

[ashawley]

@debanne Thanks for the note. This PR is just for providing a method to use the existing feature to minimize empty tags by adding a class parameter to configure as such. If there are existing issues with the pretty printer's behavior, they aren't taken up here.

So, the splitting of empty tags, making them open-close tags, and then annoyingly spreading them across two lines: That will need to be a separate issue or PR.

Here's one unit test, to get it started, though!:

  @UnitTest
  def prettyPrintAddsNewlines: Unit = {
    val pp = new xml.PrettyPrinter(4, 2)
    val x = <a/>
    // What it does:
    // assertEquals("<a>\n</a>", pp.format(x))
    // What it should do:
    assertEquals("<a/>", pp.format(x))
  }

This assumes I've understood your question.

[SethTisue]

needs rebase now.

other than that, where do we stand, here...?

[ashawley]

Rebased.

This fixes half of #46 where it doesn't have a minimize empty option. I've renamed the issue so it doesn't auto-close. The other issues in #46 will have to be taken up separately.

[hosamaly]

Could you please document the expected behaviour when this parameter is set to true? (e.g. in @param)