wxr importer uses wrong category when duplicate name exists

[tellyworth]

It's legit for two categories to have the same name when they're in different parts of a hierarchy:

Foo A
Foo Parent - Foo A

The importer gets this wrong however. It inserts both categories with the correct names and parents, but posts in the second cat will incorrectly be assigned to the first on import.

The 'Category name clash' post in this import file reproduces the problem. It should be in the Foo Parent - Foo A category, not the top level Foo A category.

​http://svn.automattic.com/wordpress-tests/wp-testdata/export/asdftestblog1.2007-12-10.xml

[tellyworth]

The exporter is part of the problem here - it lists post categories by name rather than by a unique identifier.

[edir]

I got the same problem, using version WPMU 2.9.2, discussing here.
​http://wordpress.org/support/topic/401799

[nacin]

(In [15961]) Importer and exporter overhaul, mega props duck.

Exporter overhaul:

• Add author information to export
• Greater usage of slug identifiers
• Don't export auto-drafts, spam comments, or edit lock/last meta keys
• Inline documentation improvements
• Remove filtering for now (@todo)
• Bump WXR version to 1.1, but remain back compat in the importer

Importer overhaul (​http://plugins.trac.wordpress.org/changeset/304249):

• Use an XML parser where available (SimpleXML, XML Parser)
• Proper import support for navigation menus
• Many bug fixes, specifically improvements to category and custom taxonomy handling
• Better author/user mapping

Fixes #5447 #5460 #7400 #7973 #8471 #9237 #10319 #11118 #11144 #11354 #11574 #12685 #13364 #13394 #13453 #13454 #13627 #14306 #14442 #14524 #14750 #15055 #15091 #15108.

See #15197.