[users at bb.net] How to use regular expressions in steps.ShellCommand?

[kipade]

I want to use tar to compress a directory into a single
tarbar file. I write buildstep like:

factory.addStep(steps.ShellCommand(command=["tar", "czvf", "rootfs.tar.gz", "rootfs/*"])

but I will got an error about no such file ‘rootfs/*',
it seems buildbot add a paire quote to my regular expression
string rootfs/*, but I just want it send all the command
to shell directly.
What should I do to avoiding such failure?

Regards,
-- 
kipade <kipade at 163.com>