cleanup
IDEA-128659 PluginManagerUISettings should not save defaults
EA-59075 - assert: DocumentImpl.setInBulkUpdate
New project/module wizard in IDEA Community doesn't have an option to create Dart project
[git] remove the created changelist, not the possibly null returned one

+ add a check that changesMoved receives even initiated by us
[git] fix deadlocks in cherry-pick, including IDEA-95523

Refresh changes in the background (fixes IDEA-95523),
invoke callback in the background as well (fixes newly introduced
lock with waiting in the EDT).
simplier code for tolerating of 0 got from File.getUsableSpace several times in a row