mercurial/templates/json/changelist.tmpl

templatekw: add {path} keyword to host documentation

It's hidden since I'm not sure if filectx templates can be a thing. The plan
is to add {status}, {size}, etc., which are usable within {files % ...}
context.

\{
  "node": {node|json},
  "changeset_count": {changesets|json},
  "changesets": [{join(entries%changelistentry, ", ")}]
}