mbostock/topojson — pull request #184 by jasondavies (2014-07-16 12:08:26+00:00)
Title: Remove successive coincident arcs from rings.

Quantisation can introduce coincident arcs. If this occurs during
pre-quantisation, it can result in awkward topologies, violating
assumptions made by topojson.mergeArcs.

Ideally we’d like to remove all coincident arcs from polygons, including
those generating when quantising an isthmus (which splits a ring into
two). Removing successive coincident arcs should fix the most common
cases for now, and doesn’t require splitting rings.

Related discussion in #164.