boltdb/bolt — pull request #212 by mkobetic (2014-06-24 16:05:11+00:00)
Title: Improve Stats.Sub()

Few tweaks to Stats.Sub() to make it more usable.
* Return the receiver stats fields that aren't subtracted (rather than zeros)
* Subtract TxN
* Guard against nil pointers

@benbjohnson

/cc @snormore @charlescng