mapbox/tilemill — pull request #1026 by incanus (2011-12-15 23:35:09+00:00)
Title: refs #1014: allow runtime switching of live/dev appcast

First cut; needs testing. @willwhite, not positive if you had a specific dev appcast URL in mind, but see https://github.com/mapbox/tilemill/commit/2373e1fe71ba38b0fc2fb17cc6a4e9199e4b847b#L1R17 for what I went with.