shove comes to shovel

"If push comes to shove" means that a slight push will escalate into a fight, then this means that you're fighting the opponents until you have to bury them. In other words, this is the next step up in escalation, often as an extreme last-resort measure.

"Hey Mark, aren't you supposed to be studying for finals instead the Saturday night happy hour?"
"Nah, it's in 2 weeks, so I'll just wing it and study at a relaxed pace."
"Bro. You DO know that it's actually next week, right?"
"Oh damn, I gotta get studying! If push comes to shove, I'll just wing it all throughout the week though."
"But Mr. Smith's test is on Monday!"
"Now it looks like the time when shove comes to shovel... I'm gonna have to pull an all-nighter or two."