Formalize ZeroSamplePair as return value for non-existing samples.
Change LastSamplePairForFingerprint to return a SamplePair (and not a
pointer to it), which saves allocations in a potentially extremely
frequent call.
This is with `golint -min_confidence=0.5`.
I left several lint warnings untouched because they were either
incorrect or I felt it was better not to change them at the moment.
This commit adds a federation handler on /federate. It accepts `match[]`
query parameters containing vector selectors. Their intersection determines
the in-memory metrics that are returned in the same way as the
/metrics endpoint does (modulo sorting).
beorn7
Fabian Reinartz
Julius Volz