-- Where inside its repository a module lives.
--
-- novox/hq ADR 0069. A module is a repository and a path within it. The mesh recorded the
-- repository and the ref and not the path, which was survivable only while every module was
-- assumed to sit at a repository's root — an assumption that matched nothing that exists. The
-- catalogue holds its modules one to a directory, and the system this replaces has always built a
-- module from a repository and a path.
--
-- Without this column the mesh can record that a module's source has moved ahead of what it holds
-- and then be unable to rebuild it, because it cannot say which part of the repository the module
-- is. That is the failure this prevents: noticing, and then not being able to act.
--
-- Empty rather than null, and defaulted, because "the repository's root" is a real answer and the
-- ordinary one — not an absence. Every module recorded before this keeps exactly the meaning it
-- had.
alter table module add column source_path text not null default '';