This unifies much of the logic behind them:
- All four will now ofllow the rule that the earlier file and earlier
assignment in the .d/ directories wins. Before, sysctl was the only
outlier, where the later setting always won.
- All four now support getopt() and --help on the command line.
- All four can now handle specification of configuration file names on
the command line to apply. The tools will automatically find them, and
apply them. Previously only tmpfiles could do that. This is useful for
%post scripts in RPMs and suchlike.
- This fixes various error path issues in conf_files_list()
The ability to start a new unit with 'systemctl start ...' should not
depend on whether there are other units in the directory. Previously,
an additional 'systemctl daemon-reload' would be necessary to tell
systemd to update the list of unit lookup paths.
In cases where path_strv_canonicalize() returns NULL, strv_free() is
called afterwards and it will call free() on pointers which were freed
already in path_strv_canonicalize()
- Make writing/reading of /etc/timezone dependendent of HAVE_SYSV_COMPAT
- Introduce symlink_atomic() after all, and use it
- Use relative symlink for /etc/localtime
