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test-tool synthesize: add precomputed SHA-256 pack for 4 GiB + 1

2026-05-09T02:25:32Z

Add a SHA-256 entry to the fast_packs[] table. The pack prefix and deflate block structure are identical to SHA-1 (the pack format does not encode the hash algorithm in its header). Only the suffix differs: SHA-256 OIDs are 32 bytes instead of 20, giving a 609-byte suffix compared to 513 for SHA-1, and a different pack checksum. The constants were generated by running the generic path inside a repository initialized with --object-format=sha256. Assisted-by: Claude Opus 4.6 Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

test-tool synthesize: precompute pack for 4 GiB + 1

2026-05-09T02:25:32Z

The synthesize helper hashes roughly 8 GiB of data through SHA-1 to produce a 4 GiB + 1 pack (4 GiB for the pack checksum, 4 GiB for the blob OID). Since the blob content is all NUL bytes, every byte in the resulting pack file is deterministic for a given blob size and hash algorithm. Add a fast path that writes the pack from precomputed constants: a 25-byte prefix (pack header, object header, zlib header, first block header), the zero-filled bulk with periodic 5-byte deflate block headers, and a 513-byte suffix (tree, two commits, empty tree, pack SHA-1 checksum). This eliminates all SHA-1 and adler32 computation, making the helper purely I/O-bound. The precomputed constants are stored in a struct fast_pack array keyed by hash algorithm format_id, so that adding SHA-256 support later requires only adding another array entry with its suffix. The constants were generated by running the generic path and extracting the non-zero bytes from the resulting pack file. Benchmarks generating a 4 GiB + 1 pack (3 runs each, SHA1DC on x86_64): generic path: 88s / 81s / 140s fast path: 14s / 13s / 15s On CI, where t5608 currently takes 200-850 seconds depending on the job, the fast path cuts the pack-generation phase from minutes to seconds, leaving only the clone operations themselves. Assisted-by: Claude Opus 4.6 Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

test-tool synthesize: use the unsafe hash for speed

2026-05-09T02:25:32Z

Jeff King pointed out on the mailing list [1] that t5608's new >4GB test cases dominate the entire test suite runtime: 160 seconds on his laptop when the rest of the suite finishes in under 90 seconds, and 305-850 seconds across CI jobs. The bottleneck is that the synthesize helper hashes roughly 8 GB of data through SHA-1 (4 GB for the pack checksum plus 4 GB for the blob OID) for a 4 GB+1 blob. Since the helper generates known test data, collision detection is unnecessary. Switch from repo->hash_algo to unsafe_hash_algo(), which uses hardware-accelerated SHA-1 (via OpenSSL or Apple CommonCrypto) when available. Benchmarks on an x86_64 machine generating a 4 GB+1 pack (2 runs each, interleaved): SHA-1 backend Run 1 Run 2 SHA1DC (safe) 75s 80s OpenSSL (unsafe) 21s 19s The effect scales linearly. At 64 MB with 10 randomized interleaved runs, the OpenSSL unsafe backend shows a 5.4x improvement (median 0.202s vs 1.088s) with tight variance (stdev 0.028s vs 0.095s). The speedup is only realized when the build has a fast unsafe backend compiled in. The CI's linux-TEST-vars job already sets OPENSSL_SHA1_UNSAFE=YesPlease; macOS benefits from Apple CommonCrypto when configured. On builds without a separate unsafe backend (such as the default Windows builds), unsafe_hash_algo() returns the regular collision-detecting implementation and the change is a no-op. [1] https://lore.kernel.org/git/20260501063805.GA2038915@coredump.intra.peff.net/ Assisted-by: Claude Opus 4.6 Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

test-tool: add a helper to synthesize large packfiles

2026-05-09T02:25:32Z

To test Git's behavior with very large pack files, we need a way to generate such files quickly. A naive approach using only readily-available Git commands would take over 10 hours for a 4GB pack file, which is prohibitive. Side-stepping Git's machinery and actual zlib compression by writing uncompressed content with the appropriate zlib header makes things much faster. The fastest method using this approach generates many small, unreachable blob objects and takes about 1.5 minutes for 4GB. However, this cannot be used because we need to test git clone, which requires a reachable commit history. Generating many reachable commits with small, uncompressed blobs takes about 4 minutes for 4GB. But this approach 1) does not reproduce the issues we want to fix (which require individual objects larger than 4GB) and 2) is comparatively slow because of the many SHA-1 calculations. The approach taken here generates a single large blob (filled with NUL bytes), along with the trees and commits needed to make it reachable. This takes about 2.5 minutes for 4.5GB, which is the fastest option that produces a valid, clonable repository with an object large enough to trigger the bugs we want to test. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

Merge branch 'tb/incremental-midx-part-3.2'

2026-03-25T19:58:04Z

Further work on incremental repacking using MIDX/bitmap * tb/incremental-midx-part-3.2: midx: enable reachability bitmaps during MIDX compaction midx: implement MIDX compaction t/helper/test-read-midx.c: plug memory leak when selecting layer midx-write.c: factor fanout layering from `compute_sorted_entries()` midx-write.c: enumerate `pack_int_id` values directly midx-write.c: extract `fill_pack_from_midx()` midx-write.c: introduce `midx_pack_perm()` helper midx: do not require packs to be sorted in lexicographic order midx-write.c: introduce `struct write_midx_opts` midx-write.c: don't use `pack_perm` when assigning `bitmap_pos` t/t5319-multi-pack-index.sh: fix copy-and-paste error in t5319.39 git-multi-pack-index(1): align SYNOPSIS with 'git multi-pack-index -h' git-multi-pack-index(1): remove non-existent incompatibility builtin/multi-pack-index.c: make '--progress' a common option midx: introduce `midx_get_checksum_hex()` midx: rename `get_midx_checksum()` to `midx_get_checksum_hash()` midx: mark `get_midx_checksum()` arguments as const

Merge branch 'ps/unit-test-c-escape-names.txt'

2026-03-19T16:54:56Z

The unit test helper function was taught to use backslash + mnemonic notation for certain control characters like "\t", instead of octal notation like "\011". * ps/unit-test-c-escape-names.txt: test-lib: print escape sequence names

test-lib: print escape sequence names

2026-03-11T18:38:54Z

When printing expected/actual characters in failed checks, use their names (\a, \b, \n, ...) instead of their octal representation, making it easier to read. Add tests to test-example-tap.c Update t0080-unit-test-output.sh to match the desired output Teach 'print_one_char()' the equivalent name Signed-off-by: Pablo Sabater Signed-off-by: Junio C Hamano

Merge branch 'ps/refs-for-each'

2026-03-09T21:36:55Z

Code refactoring around refs-for-each-* API functions. * ps/refs-for-each: refs: replace `refs_for_each_fullref_in()` refs: replace `refs_for_each_namespaced_ref()` refs: replace `refs_for_each_glob_ref()` refs: replace `refs_for_each_glob_ref_in()` refs: replace `refs_for_each_rawref_in()` refs: replace `refs_for_each_rawref()` refs: replace `refs_for_each_ref_in()` refs: improve verification for-each-ref options refs: generalize `refs_for_each_fullref_in_prefixes()` refs: generalize `refs_for_each_namespaced_ref()` refs: speed up `refs_for_each_glob_ref_in()` refs: introduce `refs_for_each_ref_ext` refs: rename `each_ref_fn` refs: rename `do_for_each_ref_flags` refs: move `do_for_each_ref_flags` further up refs: move `refs_head_ref_namespaced()` refs: remove unused `refs_for_each_include_root_ref()`

Merge branch 'ar/run-command-hook-take-2'

2026-03-09T21:36:55Z

Use the hook API to replace ad-hoc invocation of hook scripts via the run_command() API. * ar/run-command-hook-take-2: builtin/receive-pack: avoid spinning no-op sideband async threads receive-pack: convert receive hooks to hook API receive-pack: convert update hooks to new API run-command: poll child input in addition to output hook: add jobs option reference-transaction: use hook API instead of run-command transport: convert pre-push to hook API hook: allow separate std[out|err] streams hook: convert 'post-rewrite' hook in sequencer.c to hook API hook: provide stdin via callback run-command: add stdin callback for parallelization run-command: add helper for pp child states t1800: add hook output stream tests

Merge branch 'ps/fsck-stream-from-the-right-object-instance'

2026-03-05T18:04:49Z

"fsck" iterates over packfiles and its access to pack data caused the list to be permuted, which caused it to loop forever; the code to access pack data by "fsck" has been updated to avoid this. * ps/fsck-stream-from-the-right-object-instance: pack-check: fix verification of large objects packfile: expose function to read object stream for an offset object-file: adapt `stream_object_signature()` to take a stream t/helper: improve "genrandom" test helper