A single negation (!) rule in .graphifyignore disables all directory pruning

[papinto]

Summary

If .graphifyignore contains any negation pattern (!…), directory-level
pruning is switched off for the entire detect() walk. The walk then
descends into every ignored directory — node_modules/, bin/, obj/,
.git/, graphify-out/, etc. — even though those are still excluded from the
output. On a large repo this is a major, silent slowdown.

Output stays correct (the per-file _is_ignored filter still drops those
files), so this is a walk-performance bug, not a correctness bug — but the
detection pass can take dramatically longer than it should.

Where it happens

graphify/detect.py (verified on v0.8.37 / current v8 HEAD):

• detect.py:1047 — has_negation = any(p.startswith("!") for _, p in ignore_patterns)
• detect.py:1051 — directory kept if (has_negation or not _is_ignored(...))

Because has_negation is computed once for the whole walk, one unrelated !
rule keeps every ignored directory in the traversal.

Why it matters

The natural way to do a scoped build is a repo-wide exclude plus a re-include —
e.g. ignore everything but docs/:

node_modules/
*.md
!docs/**

That single !docs/** rule silently makes the scan walk the whole tree,
including all of node_modules/. We hit this building a docs-only graph: the
scoped extract appeared to hang because it was descending into every
node_modules/.

Repro

mkdir -p proj/bin/Debug proj/docs && echo x=1 > proj/bin/Debug/a.py
printf 'bin/\n*.md\n!docs/**\n' > proj/.graphifyignore
# detection descends into bin/ (a pattern-ignored, non-noise dir) despite the bin/ rule

Expected

A negation should re-include matching files without disabling pruning of
unrelated ignored directories. _is_ignored already honours negations
correctly — last-match-wins lets !dir/ un-ignore a directory (so it isn't
pruned), and gitignore's parent-exclusion rule means a ! cannot rescue a file
beneath an excluded directory — so descending an ignored directory to find a
re-included file is never necessary. Pruning can rely purely on _is_noise_dir

• _is_ignored.

Workaround (until fixed)

Keep .graphifyignore negation-free for large/whole-repo scans; for a scoped
build, place an ancestor-scoped inner ignore (e.g. a docs/.graphifyignore
with !*.md) instead of a root-level re-include.

I have a fix + regression test ready and will open a PR shortly.