Binary test data is not fully covered by .gitattributes and can be mangled by EOL conversion #146

Binary test data under TestCommon/Data is only partly covered by the binary rules in
.gitattributes, so some of it is stored as text and is exposed to end-of-line conversion.

.gitattributes sets * text=auto eol=lf and then names specific binary paths:

assetbundle binary
scenes binary
level* binary
*.dll binary
*.dylib binary
*.so binary
...

Unity data files whose names do not match those patterns fall through to text=auto, which leaves
the decision to git's heuristic — and that only looks for a NUL byte in the first 8000 bytes.

sharedassets0.assets.resS is the clearest case. It is 512 KB with just 8 NUL bytes, none of them
early, so git classifies it as text:

$ git check-attr -a TestCommon/Data/PlayerWithTypeTrees/sharedassets0.assets.resS
... text: auto
... eol: lf

$ git diff --numstat <commit-that-added-it>
1   0   TestCommon/Data/PlayerWithTypeTrees/sharedassets0.assets.resS

(A file git considered binary shows - - there, as the .assets and level* files in the same
folder do.)

Nothing is corrupted today. Both checked-in .resS files happen to contain zero CR bytes, so
eol=lf normalization is a no-op and they round-trip byte for byte — verified by comparing the
SHA-256 of the blob in git against the source file. This is a latent hazard, not a live bug.

The risk is the next binary fixture whose bytes happen to include 0d 0a. On checkout it would
have those bytes rewritten to 0a, producing a corrupt file that still looks plausible, and the
resulting test failure would point at the parser rather than at git. Anything without an extension
already covered by a binary rule is affected — .resS, .resource, .assets, .bundle,
.buildreport, .cf, and the extensionless CAB-* files.

Suggested fix: mark the data folder's binary formats explicitly, e.g.

TestCommon/Data/** -text

or per-extension binary rules for *.resS, *.resource, *.assets, *.bundle, *.buildreport,
*.cf alongside the existing ones. Worth checking afterwards that no already-committed file changes
content (they should not — the ones that would have been mangled are the ones that do not exist
yet), and that the README.md files inside TestCommon/Data are not caught by a blanket rule.

Found while adding Unity 6.7 test data in #145, where the new .resS reproduced the same
classification.