combine /usr/bin/df and /usr/xpg4/bin/df
Per Garrett D'Amore:
Looking at the code, it appears that the only differences for XPG4 in the command are:
a) support for
P (which could be added trivially - indeed it probably should be.)
b) the specific header text used (and as a result, the spacing of some of the columns)
Those differences are stupid. We should just collapse them.