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Two of the packfile tests build a small pack in memory and then point into it with byte offsets written as constants. Those constants only hold if zlib turns "Hello" into 17 bytes and "Hello!\n" into 19, which was true through Go 1.26. Go 1.27 breaks that. It writes these short inputs as a stored block, so each comes out one byte longer. The OFS_DELTA test then points one byte past the base object's header and lands on the zlib header byte, which decodes as an OBJ_REF_DELTA. The index lookup fails with "object not found in index" and the test panics on the nil object. The REF_DELTA test has the same problem with its index entry. Both values are now computed from len(compressed), so the tests stop depending on how many bytes the compressor emits. Tested with Go 1.25.0, 1.26.0 and 1.27.1.
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Two tests in pack/packfile_test.go fail under Go 1.27. I hit this
building the Debian package, where
TestPackObjectReturnsObjectWithDeltaBaseOffset panics with a nil
pointer dereference.
Both tests hardcode offsets that assume zlib compresses "Hello" to 17
bytes and "Hello!\n" to 19. Go 1.27 emits 18 and 20, so the offsets
land on the wrong bytes. This computes them from len(compressed)
instead.
go test ./...passes with Go 1.25.0, 1.26.0 and 1.27.1. CI onlycovers 1.25 and 1.26 right now, so it won't show the original failure.
Adding 1.27.x to the matrix could be a separate change.