phases: add a very simple test Note that the expected output is wrong as is should be phase-1. But the machinery to plant new root is to come in later commit.

phases: add a phase template keyword

phases: add a phase method to context

phases: add a cache allowing to know in which phase a changeset is

phases: handle errors other than ENOENT appropriately

phases: basic I/O logic Add function to read and write phase roots. Add a _phaseroots filecache on localrepo class to access the phaseroots data.