git/commit-graph.c, branch v2.48.0

Merge branch 'ps/build-sign-compare'

2024-12-23T17:32:11Z

Start working to make the codebase buildable with -Wsign-compare. * ps/build-sign-compare: t/helper: don't depend on implicit wraparound scalar: address -Wsign-compare warnings builtin/patch-id: fix type of `get_one_patchid()` builtin/blame: fix type of `length` variable when emitting object ID gpg-interface: address -Wsign-comparison warnings daemon: fix type of `max_connections` daemon: fix loops that have mismatching integer types global: trivial conversions to fix `-Wsign-compare` warnings pkt-line: fix -Wsign-compare warning on 32 bit platform csum-file: fix -Wsign-compare warning on 32-bit platform diff.h: fix index used to loop through unsigned integer config.mak.dev: drop `-Wno-sign-compare` global: mark code units that generate warnings with `-Wsign-compare` compat/win32: fix -Wsign-compare warning in "wWinMain()" compat/regex: explicitly ignore "-Wsign-compare" warnings git-compat-util: introduce macros to disable "-Wsign-compare" warnings

global: mark code units that generate warnings with `-Wsign-compare`

2024-12-06T11:20:02Z

Mark code units that generate warnings with `-Wsign-compare`. This allows for a structured approach to get rid of all such warnings over time in a way that can be easily measured. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano

packfile: pass down repository to `for_each_packed_object`

2024-12-03T23:21:54Z

The function `for_each_packed_object` currently relies on the global variable `the_repository`. To eliminate global variable usage in `packfile.c`, we should progressively shift the dependency on the_repository to higher layers. Let's remove its usage from this function and closely related function `is_promisor_object`. Signed-off-by: Karthik Nayak Signed-off-by: Junio C Hamano

packfile: add repository to struct `packed_git`

2024-12-03T23:21:53Z

The struct `packed_git` holds information regarding a packed object file. Let's add the repository variable to this object, to represent the repository that this packfile belongs to. This helps remove dependency on the global `the_repository` object in `packfile.c` by simply using repository information now readily available in the struct. We do need to consider that a packfile could be part of the alternates of a repository, but considering that we only have one repository struct and also that we currently anyways use 'the_repository', we should be OK with this change. We also modify `alloc_packed_git` to ensure that the repository is added to newly created `packed_git` structs. This requires modifying the function and all its callee to pass the repository object down the levels. Helped-by: Taylor Blau Signed-off-by: Karthik Nayak Signed-off-by: Junio C Hamano

commit-graph: remove unnecessary UNLEAK

2024-09-23T17:03:59Z

When f4dbdfc4d5 (commit-graph: clean up leaked memory during write, 2018-10-03) added the UNLEAK, it was right before a call to die_errno(). e103f7276f (commit-graph: return with errors during write, 2019-06-12) made it unnecessary, as it was then followed by a free() call for the allocated string. The code moved to write_commit_graph_file() in the meantime and the string pointer is now part of a struct, but the function's only caller still cleans up the allocation. Drop the superfluous UNLEAK. Signed-off-by: René Scharfe Signed-off-by: Junio C Hamano

refs: add referent to each_ref_fn

2024-08-09T15:47:34Z

Add a parameter to each_ref_fn so that callers to the ref APIs that use this function as a callback can have acess to the unresolved value of a symbolic ref. Signed-off-by: John Cai Signed-off-by: Junio C Hamano

Merge branch 'tb/path-filter-fix'

2024-07-08T21:53:10Z

The Bloom filter used for path limited history traversal was broken on systems whose "char" is unsigned; update the implementation and bump the format version to 2. * tb/path-filter-fix: bloom: introduce `deinit_bloom_filters()` commit-graph: reuse existing Bloom filters where possible object.h: fix mis-aligned flag bits table commit-graph: new Bloom filter version that fixes murmur3 commit-graph: unconditionally load Bloom filters bloom: prepare to discard incompatible Bloom filters bloom: annotate filters with hash version repo-settings: introduce commitgraph.changedPathsVersion t4216: test changed path filters with high bit paths t/helper/test-read-graph: implement `bloom-filters` mode bloom.h: make `load_bloom_filter_from_graph()` public t/helper/test-read-graph.c: extract `dump_graph_info()` gitformat-commit-graph: describe version 2 of BDAT commit-graph: ensure Bloom filters are read with consistent settings revision.c: consult Bloom filters for root commits t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()`

Merge branch 'ps/use-the-repository'

2024-07-02T16:59:00Z

A CPP macro USE_THE_REPOSITORY_VARIABLE is introduced to help transition the codebase to rely less on the availability of the singleton the_repository instance. * ps/use-the-repository: hex: guard declarations with `USE_THE_REPOSITORY_VARIABLE` t/helper: remove dependency on `the_repository` in "proc-receive" t/helper: fix segfault in "oid-array" command without repository t/helper: use correct object hash in partial-clone helper compat/fsmonitor: fix socket path in networked SHA256 repos replace-object: use hash algorithm from passed-in repository protocol-caps: use hash algorithm from passed-in repository oidset: pass hash algorithm when parsing file http-fetch: don't crash when parsing packfile without a repo hash-ll: merge with "hash.h" refs: avoid include cycle with "repository.h" global: introduce `USE_THE_REPOSITORY_VARIABLE` macro hash: require hash algorithm in `empty_tree_oid_hex()` hash: require hash algorithm in `is_empty_{blob,tree}_oid()` hash: make `is_null_oid()` independent of `the_repository` hash: convert `oidcmp()` and `oideq()` to compare whole hash global: ensure that object IDs are always padded hash: require hash algorithm in `oidread()` and `oidclr()` hash: require hash algorithm in `hasheq()`, `hashcmp()` and `hashclr()` hash: drop (mostly) unused `is_empty_{blob,tree}_sha1()` functions

bloom: introduce `deinit_bloom_filters()`

2024-06-25T20:52:06Z

After we are done using Bloom filters, we do not currently clean up any memory allocated by the commit slab used to store those filters in the first place. Besides the bloom_filter structures themselves, there is mostly nothing to free() in the first place, since in the read-only path all Bloom filter's `data` members point to a memory mapped region in the commit-graph file itself. But when generating Bloom filters from scratch (or initializing truncated filters) we allocate additional memory to store the filter's data. Keep track of when we need to free() this additional chunk of memory by using an extra pointer `to_free`. Most of the time this will be NULL (indicating that we are representing an existing Bloom filter stored in a memory mapped region). When it is non-NULL, free it before discarding the Bloom filters slab. Suggested-by: Jonathan Tan Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano

commit-graph: reuse existing Bloom filters where possible

2024-06-25T20:52:06Z

In an earlier commit, a bug was described where it's possible for Git to produce non-murmur3 hashes when the platform's "char" type is signed, and there are paths with characters whose highest bit is set (i.e. all characters >= 0x80). That patch allows the caller to control which version of Bloom filters are read and written. However, even on platforms with a signed "char" type, it is possible to reuse existing Bloom filters if and only if there are no changed paths in any commit's first parent tree-diff whose characters have their highest bit set. When this is the case, we can reuse the existing filter without having to compute a new one. This is done by marking trees which are known to have (or not have) any such paths. When a commit's root tree is verified to not have any such paths, we mark it as such and declare that the commit's Bloom filter is reusable. Note that this heuristic only goes in one direction. If neither a commit nor its first parent have any paths in their trees with non-ASCII characters, then we know for certain that a path with non-ASCII characters will not appear in a tree-diff against that commit's first parent. The reverse isn't necessarily true: just because the tree-diff doesn't contain any such paths does not imply that no such paths exist in either tree. So we end up recomputing some Bloom filters that we don't strictly have to (i.e. their bits are the same no matter which version of murmur3 we use). But culling these out is impossible, since we'd have to perform the full tree-diff, which is the same effort as computing the Bloom filter from scratch. But because we can cache our results in each tree's flag bits, we can often avoid recomputing many filters, thereby reducing the time it takes to run $ git commit-graph write --changed-paths --reachable when upgrading from v1 to v2 Bloom filters. To benchmark this, let's generate a commit-graph in linux.git with v1 changed-paths in generation order[^1]: $ git clone git@github.com:torvalds/linux.git $ cd linux $ git commit-graph write --reachable --changed-paths $ graph=".git/objects/info/commit-graph" $ mv $graph{,.bak} Then let's time how long it takes to go from v1 to v2 filters (with and without the upgrade path enabled), resetting the state of the commit-graph each time: $ git config commitGraph.changedPathsVersion 2 $ hyperfine -p 'cp -f $graph.bak $graph' -L v 0,1 \ 'GIT_TEST_UPGRADE_BLOOM_FILTERS={v} git.compile commit-graph write --reachable --changed-paths' On linux.git (where there aren't any non-ASCII paths), the timings indicate that this patch represents a speed-up over recomputing all Bloom filters from scratch: Benchmark 1: GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths Time (mean ± σ): 124.873 s ± 0.316 s [User: 124.081 s, System: 0.643 s] Range (min … max): 124.621 s … 125.227 s 3 runs Benchmark 2: GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths Time (mean ± σ): 79.271 s ± 0.163 s [User: 74.611 s, System: 4.521 s] Range (min … max): 79.112 s … 79.437 s 3 runs Summary 'GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths' ran 1.58 ± 0.01 times faster than 'GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths' On git.git, we do have some non-ASCII paths, giving us a more modest improvement from 4.163 seconds to 3.348 seconds, for a 1.24x speed-up. On my machine, the stats for git.git are: - 8,285 Bloom filters computed from scratch - 10 Bloom filters generated as empty - 4 Bloom filters generated as truncated due to too many changed paths - 65,114 Bloom filters were reused when transitioning from v1 to v2. [^1]: Note that this is is important, since `--stdin-packs` or `--stdin-commits` orders commits in the commit-graph by their pack position (with `--stdin-packs`) or in the raw input (with `--stdin-commits`). Since we compute Bloom filters in the same order that commits appear in the graph, we must see a commit's (first) parent before we process the commit itself. This is only guaranteed to happen when sorting commits by their generation number. Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano