Lights in my outdoor enclosure

So, I have an outdoor working area covered by a tarp-garage. It is up against my building covering a window.

I have two florescent lamps of the ballast variety that I'm hoping to affix to the metal structure of the 'shed' to provide some light while I'm working.

I'm hoping to avoid bringing true electrical wiring out of the building and just bringing an extension out through the window, into the shed, and wiring up the lights with fixture cord.

Is this a bad idea? What else might be a smart thing for me to do?

I don't understand "tarp-garage" but I assume it's a temporary structure. As such, a temporary extension lead sounds OK to me. Make sure it's safe.

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