family.py add: the commit is never checked for a gitlink at exactly members/<P>, and members: null is refused as a missing members: line #920

Goal: family.py add confirms that its own commit holds the gitlink at exactly members/<P>, and reads every spelling of an empty members: line that the holder's reader reads.

Filed by lane openRepoShape-3, from its triage of #459 at the v1.1.1 release commit 5017830. It groups #459's lines U049 (#363's option 2, from #574) and U188 (RV870's NIT-3), one pull request's worth.

Check the commit after the fact (U049)

State. #574 (62ef256) refuses the known causes of a misplaced gitlink, the case variants of members/, before the mount. Nothing checks the result: _commit_one (scripts/family.py:1757) reads no git ls-tree HEAD for the new gitlink. PR #574's body left it out: "The ruling refuses before the mount, so nothing here needs it."

What happens. A cause nobody foresaw would commit a misplaced gitlink, and fresh clones would leave the member empty.

Evidence. scripts/family.py:1757 at 5017830; PR #574's body.

Direction. After the commit, read git ls-tree HEAD for a gitlink at exactly members/<P>. If it is anywhere else, undo the command's own commit and mount, and refuse with the spelling git chose.

members: null is refused as no members: line (U188)

State. add's line finder takes only ("members:", "members: []") (scripts/family.py:423), and otherwise raises family-members-unrecognised with "has 0 members: line(s)" (:430-437). _checked_members_readable lets a null through to the verbs (:468-469: "Absent or null is no members"). def45de (#870, #864) left the finder as it was.

What happens. A holder whose family.yaml says members: null, with the null written as a word (or ~), is refused by add with a reason that is untrue: the line is there, and the readers read it as null. Nothing is written. Measured by RV870 on #870's head 03fe51e6; the same on main.

Evidence. scripts/family.py:420-437 at 5017830:

if line.rstrip() in ("members:", "members: []"):

Direction. Have the finder take each null spelling the parser reads (null, Null, NULL, ~) as it takes members:, so add writes the first member there; otherwise have the refusal name the null. One test per spelling.

Size: S.

Lane: openreposhape-3 (openRepoShape-3)