Detect ordering-only differences in XML files
*This bug was originally reported by Paul Wise (@pabs) in Debian bug [#1022146](https://bugs.debian.org/1022146):*
```
Package: diffoscope
Version: 224
Severity: wishlist
It would be nice if diffoscope could detect that XML files are only
different because of ordering differences, currently it cannot:
$ head -vn-0 *.xml
==> bar.xml <==
<?xml version='1.0' encoding='UTF-8' ?>
<foo>
<bar attr='bar'/>
<bar attr='foo'/>
</foo>
==> foo.xml <==
<?xml version='1.0' encoding='UTF-8' ?>
<foo>
<bar attr='foo'/>
<bar attr='bar'/>
</foo>
$ diffoscope *.xml
--- bar.xml
+++ foo.xml
│ --- bar.xml
├── +++ foo.xml
│ @@ -1,5 +1,5 @@
│ <?xml version="1.0" encoding="utf-8"?>
│ <foo>
│ - <bar attr="bar"/>
│ <bar attr="foo"/>
│ + <bar attr="bar"/>
│ </foo>
$ echo $?
1
```
issue