Michael Kuhn 53ddefa0df Fix shift warning on zsh (#8805) ... When using zsh, trying to shift when there are no arguments left results in warnings like this: spack:shift:22: shift count must be <= $#		2018-07-27 08:14:01 -05:00
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spack	Fix shift warning on zsh (#8805)	2018-07-27 08:14:01 -05:00