When you have some temporary files or new files that are not going to be part of your next commit, you exclude them in the commit window. While selective commit on line/hunk level isn't possible yet, complete excluding is and it's frequently used.
The "Diff" tab of commit window also has a line through on excluded files but when you select the full diff it will include those files and the diff can be a bit confusing as it doesn't reflect what you would probably expect.
hmm, did help only for files excluded before the commit window has been open/
along with this fix it should work now as you expect...
Integrated into 'main-silver', will be available in build *201411200001* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
User: Ondrej Vrabec <email@example.com>
Log: #248711 - Full textual diff in commit window should exclude excluded files
Filter out excluded files before showing the overall diff.