take increasingly bigger steps

[matthiaskrgr]

After some time, bisect will always check 2 rust versions per month as it goes back in time, but when bisecting stable-to-stable regressions, this still takes a lot of time. It would be nice if could perhaps try to go back by one month at a time a year after the first checked commit and maybe 1.5 months after 2 years? (or just increase the number of days skipped linearly with the further back we go?)

[oli-obk]

we could also just go back exponentially by default and then do a normal bisection when we hit a change

[Mark-Simulacrum]

The choice here was intentional, in my experience the farther back you go the more likely it is that you stop building for different reasons (typically dropping back before the relevant feature is supported), meaning that the "did it build" function is not monotonic, which means you can't bisect: you have bad commits both at the beginning and the end of your curve, which prevents the typical binary search from working.

We can tweak the exact constant, but I would avoid trying anything exponential - that goes too quickly, in my experience.

[matthiaskrgr]

Could be behind an extra cmdline flag. From doing a couple bisections today i already got around 100 bisector toolchains installed which seems like quite a lot .