Let's look at the datasheet for an MMBT3904, just for example. The absolute maximum section talks mostly about maximum voltage differences, and a single current limit - the collector current.
I'm used to using these, and similar BJTs as saturated switches. And I get that once you have a base current that is sufficient that the Hfe causes the collector current to max out... I'm good to go.
When I was a kid, I didn't know this stuff as well as I do now (which says a lot), so I tried setting up saturated BJT switches with no base resistor. So I'd pump way, way too much current from the base to emitter and blow it apart. I'm older and wiser now.
But the question still stands: From the absolute maximums on the datasheet, how do I calculate what is effectively the absolute minimum base resistor? That is, the absolute maximum amount of base current before the blue smoke is released?