Detect and reproduce external-compression level - #296
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When xdelta3 auto-decompresses an externally compressed input (bzip2, gzip, xz) and later auto-recompresses the decoded output, reproduce the original compression level so the recompressed bytes match the original. The level is detected from the stream header at encode time (bzip2 exact, gzip/xz best-effort), carried in the VCDIFF application header as "<ident><level>" (e.g. "B9"), parsed back out on decode, and passed as "-N" to the recompressor. gzip also gains "-n" so its header is reproducible. -G emits a legacy app-header (bare "<ident>") for compatibility with older xdelta3 versions, which exact-match the compressor ident and would otherwise decline to recompress a new delta's output. Old deltas (no level digit) decode unchanged. Adds testing/recompress_level_test.sh, a deterministic bzip2 round-trip regression test (registered as a CTest), covering byte-identical recompression at levels 1/5/9 and the -G legacy path. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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When xdelta3 auto-decompresses an externally compressed input (bzip2, gzip, xz) and later auto-recompresses the decoded output, reproduce the original compression level so the recompressed bytes match the original.
The level is detected from the stream header at encode time (bzip2 exact, gzip/xz best-effort), carried in the VCDIFF application header as "" (e.g. "B9"), parsed back out on decode, and passed as "-N" to the recompressor. gzip also gains "-n" so its header is reproducible.
-G emits a legacy app-header (bare "") for compatibility with older xdelta3 versions, which exact-match the compressor ident and would otherwise decline to recompress a new delta's output. Old deltas (no level digit) decode unchanged.
Adds testing/recompress_level_test.sh, a deterministic bzip2 round-trip regression test (registered as a CTest), covering byte-identical recompression at levels 1/5/9 and the -G legacy path.