After installing new packages, the M-x man command might not list the new manpages for those packages, because the whatis DB used by man gets updated weekly via a cron job. Further, any manpages for programs that are part of the XCode Commandline Tools will never get installed because the cron job inexplicably excludes them. To make force them to be generated, run the following:
sudo /etc/periodic/weekly/320.whatis
sudo /usr/libexec/makewhatis /Applications/Xcode.app/Contents/Developer/usr/share/man