shelve: store shelved node in a new data file It is useful for a version of shelve not based on bundle and strip. Having more data does not hurt the bundle based case so we introduce it in all cases before doing more rework. We also keep storing the patch using another method. note: We could have this metadata file list all the file involved in the shelve and use that for cleanup. This would be more future proof than having a hard-coded list of file to purge. However, this is an adventure for another series.

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.