I know that I can tell conda to build from github as:
source:
fn: v1.6.0.tar.gz
url: https://github.com/SciTools/iris/archive/v1.6.0.tar.gz
md5: 24c2d55758325a8f05aadf99748c0d2a
or
source:
git_url: git@github.com:SciTools/iris.git
git_tag: v1.6.0
but how would one tell conda to build from a github branch?