The repo test was `os.path.isdir(<repo>/.git)`, which is wrong in both
directions. A LINKED worktree's `.git` is a 47-byte FILE (`gitdir: ...`), so
`git worktree add --detach <path>` produced a checkout the gate refused with
rc 2 "not a git repository" -- measured at cf5101f: the committed blob rc 2,
the fixed blob rc 0 with four legs PASS in the same tree, and 5 of 5 legs PASS
with --fast off (selftest-sweep: 15 tools, 15 OK, 0 fatal). An empty directory
named `.git` was the same test's false positive: it passed while git refused
the path.
`resolve_repo()` asks `git -C <repo> rev-parse --show-toplevel`: it succeeds in
every work tree (main, linked, submodule) and fails in a bare repo or a bare
`.git` directory. `--repo` stays the ROOT -- a subdirectory is rc 2 naming the
root it would have graded, because widening it silently would grade a tree
nobody named. Legs, rcs and --queue/--index semantics are untouched.
Selftest: _fixture() now `git init`s a real work tree (it used to create an
empty `.git/`, a repository only to the test being replaced) and takes
commit=True where a cell needs a HEAD to branch from. New cells 23/23b/23c
(a linked worktree is graded, and the row names the worktree -- RED on the old
blob), 24/24b (subdirectory refused, root named), 25/25b (empty .git refused),
26 (bare repo refused). 42 -> 50 cells, 50/50, rc 0.
No queue item opened or closed; no another-party file edited.
volt
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