Your bug report

#13789: Undo (C-/) silently ignored in Homebrew emacs v24.2.1

which was filed against the emacs,ns package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 13789@debbugs.gnu.org.

-- 
13789: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=13789
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