Compare prefixes ignoring case - #1870
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The prefix set was case sensitive, but the prefix maps to file names and NTFS and APFS are both case insensitive. Test methods Foo and foo passed the uniqueness check and then silently shared one set of snapshot files. A snapshot repository has to work on every platform, so the check now ignores case everywhere rather than only where the filesystem does.
This was referenced Aug 26, 2026
This was referenced Aug 27, 2026
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PrefixUniquekept its set with the default (case sensitive) comparer, but the prefix maps to file names, and NTFS and APFS are both case insensitive. Two test methodsFooandfootherefore passed the uniqueness check and then silently shared one set of snapshot files, each overwriting the other's.The check now ignores case with
StringComparer.OrdinalIgnoreCase.A deliberate call: this applies on every platform, not only where the filesystem is case insensitive. On Linux the two prefixes really are distinct files, so this rejects something that would technically work there. That seems right for a snapshot repository — the files are committed and shared, so a pair that only differs in case is broken for everyone on Windows or macOS, and the failure should surface wherever it is authored rather than only in someone else's checkout. It is also consistent with
VerifyEngine, which already builds its delete set with an ignore-case comparer.DisableRequireUniquePrefix()remains the escape hatch.PrefixUniqueTestscovers both directions.Verify.Tests(1301),StaticSettingsTestsandVerify.NUnit.Testspass.