patch.pathtransform: add doctests
In upcoming patches we're going to make this function more complex, so add some
unit tests for it.
patch: rename pathstrip to pathtransform
In upcoming patches we'll not just strip path components but also add new ones.
templatekw: forward _hybrid.get to raw values so that get(extras, key) works
ef78450c8df6 implies that the primary goal is to allow "{get(extras, key)}",
but it didn't work.
I'm not sure if _hybrid should forward all unknown attributes to values, so
only "get" is forwarded for now.