app.Before receives a cli.Context but without flags parsed. There is no
point calling ctx.Bool() or ctx.IsSet() at that stage.
However, flags are parsed in commands, so minio initialization and
setting global variables (globalJSON, globalQuiet, etc..) can be moved
to the Before function of all commands.
Avoid setting command.Before for non leaf commands, otherwise Before
function will be called multiples times until it reaches the leaf
command.
Stat() is supposed to return valid information for existing
objects and existing prefixes as well.
The current mechanism issues a listing request and searches
for the object or prefix in the returned list, but this could take
time if there are a lot of entries under a parent prefix.
The new commit changes the internal behavior but not the
functional output. It issues a HEAD request first, if there
is no object then assumes it is a prefix and does listing
in order to find it.
