Drop space before slash in empty elements

Currently, the plug-in enforces a space before the closing slash in empty elements when xmlSelfClosingTags is true, normalizing <foo></foo> and <foo/> to <foo />.

Some projects prefer the tighter <foo/> syntax, so if an option already exists to configure empty tag handling, perhaps a third value could be added to support this convention, like:

• true (no space) – <foo/>
• false – <foo></foo>
• space (current behavior) – <foo />

If so, this setting could also be applied to the XML declaration, to permit

<?xml version="1.0" encoding="UTF-8"?>

instead of rewriting to insert an extra space before the closing ?> as noted in #3:

<?xml version="1.0" encoding="UTF-8" ?>

[kddnewton]

Ehh alright. You convinced me. I’ll release that today.

[gtwohig]

@kddnewton too bad that it was dropped as lack of this feature is a blocker for us going to 1.0.

Use case: we are cleaning up/standardizing formatting on XML that is returned to us via the Salesforce metadata API. They (salesforce) do not include a space before the ?> on the xml version line nor do they on self closing elements. With xmlSelfClosingSpace: false the only files with a diff after the pull are ones that have a substantive change. This allows pretty-quick to run super fast because only a few files need to be prettified. With the 1.0 behavior we have thousands of files with whitespace only diffs that need to be cleaned up by prettier eliminating the significant speed improvements we get from pretty-quick.