Collapse BUG_RATIO and DISCOVERY_RATIO into a single introduced work ratio?

[danielnixon]

Are BUG_RATIO and DISCOVERY_RATIO fundamentally different, or could we simplify our lives by having a single ratio for “new work”? Does treating them separately give us some benefit? Greater accuracy?

[kn-ad]

I've got an uncommitted TODO comment related to this:

// TODO: Should we use a compounding formula to account for tickets that get created and
//       then cause new tickets themselves, e.g. bugs introduced by the new features? If so,
//       should we treat the two ratios differently, since more bugs tend to be created by
//       feature tickets and bugs usually don't take as long as features?