more robust treatment of rsync on macOS (see also 96fb1f9a4042);

tuned whitespace;

more robust: no change of directory attributes of initial test, notably target without .hg_sync meta data;

merged

added lemmas reflp_on_Inf and reflp_on_Sup

replaced HOL.implies by Pure.imp in reflp_mono for consistency with other lemmas

added lemmas reflp_on_inf, reflp_on_sup, and reflp_on_mono

merged

more robust: protect_args does not work with rsync 2.x from macOS, and is not required in typical situations;

clarified context with global defaults;

tuned signature;

clarified signature: more explicit type Rsync.Context;

clarified signature;

clarified modules;

provide python-3.10.4 for darwin and linux;

provide hugo-0.88.1 for darwin and linux;

removed obsolete self_update: always enabled, notably on lxbroy10 which is the only shared-home system (and still requires current isabelle_self);

avoid redundant meta data: exclude .hg_archival.txt;

clarified remote vs. local build_history: operate on hg_sync directory instead of repository;

proper operation on String, not Path;

clarified signature: cwd can be misleading --- changes meaning of target;

merged

more meta data; clarified signature: more explicit types;

clarified signature: more operations;