adopt-project.py: a kept or dropped name reaches the split commit and the pull request body unspelled, and _spelled, _shown and plan's report print text that reads as another name, or raw #900

Goal: every name, question and rule id that adopt-project.py prints or writes reads one way only and carries no raw control byte.

Filed by lane openRepoShape-3, from its triage of #457 at the v1.1.1 release commit 5017830. It groups #457's lines A6, AS-1, AS-2, AS-3, L2-76 and L1-36, one pull request's worth.

State at 5017830.

• _split_message (adopt-project.py:13474) lists every moved, dropped and kept path as f" {path}" (:13498-13509). That message is the split commit's message and the pull request's body.
• _spelled_character (:3114-3124) writes a backtick as a backslash and a backtick, and leaves a double quote as it is, so a spelled name copied into the plan names another entry or makes the plan unreadable.
• _shown (:3100-3111) prints any printable text as it is, so a name that begins and ends with a backtick prints exactly as _spelled prints another name.
• plan's report prints a path policy's question: (:5168, :5173) and its rule id (:5495) as they are. scripts/path_classify.py asks neither to be printable. (Read, not probed.)
• _exported_gitlink (:1518) raises git-failed with the source folder and git's stderr formatted raw (:1593-1595), where git_out spells both (scripts/repo_shape.py:1211-1215).
• _print_entries (:5491) pads each name to 34 characters before stdout escapes it.

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

A source that keeps caf\xe9.md (the byte 0xE9) and cr\r in the root: check exits 0 and execute exits 0 with adoption verified. Then the split commit's message, through cat -A, reads:

  caf?.md$
  cr$

The byte is written as ?, and the trailing CR is lost, so the name now spells another path.

The two spelling functions, called directly:

'a`b'  spelled: `a\`b`   shown: a`b
'a"b'  spelled: `a"b`    shown: a"b
'`x`'  spelled: `\`x\``  shown: `x`
'x'    spelled: `x`      shown: x

plan under LC_ALL=C PYTHONUTF8=0, for a source holding caf\xe9.md:

path                               leg        conf     files rule
README.md                          root       high         1 root-front-door
caf\xe9.md                            spec       medium       1 extension-majority

Direction.

• Spell each path in _split_message as plan and check spell it.
• Spell a backtick and a double quote as \x60 and \".
• Spell a printable text that begins and ends with a backtick.
• Print a policy's question and rule id through _shown, as check prints the question.
• Build _exported_gitlink's refusal with shown_path and spelled, as git_out does, and keep the code git-failed.
• Pad the printed form of a name, not the name.

Size: M.

Lane: openreposhape-3 (openRepoShape-3)