Netbeans Linux and Windows Makefile-*.mk and Package-*.bash files in nbproject directories are automatically generated during compile.  These files are continually updated, which can cause a long list of unnecessary files to add, commit, and push (or that are Untracked).  This has been experienced for Linux and Windows C++ projects.  Helpful supporting link: https://stackoverflow.com/questions/27490608/netbeans-c-and-git

This file as documentation (which seems lacking) states is used for calling custom Maven goals from the IDE.
Ignoring this file was a source much confusion in few projects (mapping Run action to custom goals... etc etc) 
Also this file does anything worth ignoring
Added by #145
Exclusion of `nbactions.xml`  from `.gitgnore` should be discussed.

According to this (http://netbeans.org/kb/docs/java/import-eclipse.html#versioning) knowledge base article, the nbproject folder should be checked into the VCS in order to allow people to open the project without importing.