adopt-project.py check and execute: one bad plan value is named in different orders, or by two or three findings, and two pin sentences say more than execute does #901

Goal: check and execute name the same first problem in a hand-edited plan, and name each bad value once, in words that say what execute does.

Filed by lane openRepoShape-3, from its triage of #457 at the v1.1.1 release commit 5017830. It groups #457's lines L2-6, L2-7, L1-K7, L2-12 and L2-42, one pull request's worth.

State at 5017830.

• check asks the plan's id and organisation in _manifest_values (adopt-project.py:4894), while execute asks the leg paths first, in _checked_plan_values (:12030).
• _manifest_values' docstring still says "a bad date does not change which problem either command names first" (:4911-4912). That holds for the organisation and the id only. L2-7 measured that with visibility: secret beside elected_on: someday, both commands name election-date-malformed rather than plan-manifest-invalid; that was not measured again here.
• A pin whose product holds a tab is now three findings about one value.
• _read_pins spells a pins: that is not a list with repr (:554).
• Every pin finding ends "execute writes the pin file from the commit and the digest plan records, and nothing else" (:584-586). That includes the digest_source: finding (:494-498), though execute also writes that field as _digest_source_written reads it (:521).

What happens. Measured on a detached clone at 5017830, with a stub gh (exit 97), GH_TOKEN=bogus, an empty GH_CONFIG_DIR and local remotes.

id: "North Wind" and legs.spec_path: "../spec":

check exit 2
REFUSED plan-bad-id: <plan>: `id:` is 'North Wind' and must match ^[a-z0-9][a-z0-9-]*$
execute exit 2
REFUSED plan-bad-leg-path: legs.spec_path is '../spec', which is not a canonical leg path: ...
legs made: 0

org: "-evil" and the same leg path:

check exit 2
REFUSED unsafe-value: org is '-evil', which is not a value this tool will put on a `git` or `gh` command line
execute exit 2
REFUSED plan-bad-leg-path: legs.spec_path is '../spec', ...
legs made: 0

A pin edited to product: "a\t" and repository: "opensoft/a\t":

check exit 1
FINDING plan-pin-malformed: `pins:` entry 1 ('a\t') records `product: 'a\t'` and `repository: 'opensoft/a\t'`, ... `execute` writes the pin file from the commit and the digest `plan` records, and nothing else: re-run ...
FINDING plan-unwritable-value: a `pins:` item is 'a\t', which `execute` writes into the assembly root's `project.yaml`, and it holds a control character
FINDING plan-manifest-invalid: the manifest this run would write is one the project's own validate-manifest.py refuses: manifest-neutral-product-pins: neutral_product_pins entry 'a\t' is not a neutral product name: it holds a character that is not printable.

Direction.

• Ask the plan's options in one order in both commands, so both name the same first problem.
• Reword the docstring: "so a bad date beside a bad organisation or id does not make check and execute name different problems first".
• Let one rule leave a value that another rule names.
• Spell pins: with _read_as(rows).
• End the digest_source: finding with "and how it was read, and nothing else", or give it a sentence of its own.

Size: M.

Lane: openreposhape-3 (openRepoShape-3)