shelve: mention FILE options in help
Shelve do normally take a list of files or patterns to shelve and the command
summary should thus show [FILE]...
Note: --delete is a bit special and interpret the parameters as a list of
shelve names. This change makes that even less obvious from the help. Too bad
- we can't please everyone.
shelve: really pass publicancestors to changegroupsubset - not the parents
publicancestors returned the parents of the public ancestors ... and
changegroupsubset used the parents of these as base for the bundle. That gave
bundles with one layer of changesets more than necessary.