* ps/object-wo-the-repository:
hash: stop depending on `the_repository` in `null_oid()`
hash: fix "-Wsign-compare" warnings
object-file: split out logic regarding hash algorithms
delta-islands: stop depending on `the_repository`
object-file-convert: stop depending on `the_repository`
pack-bitmap-write: stop depending on `the_repository`
pack-revindex: stop depending on `the_repository`
pack-check: stop depending on `the_repository`
environment: move access to "core.bigFileThreshold" into repo settings
pack-write: stop depending on `the_repository` and `the_hash_algo`
object: stop depending on `the_repository`
csum-file: stop depending on `the_repository`
As a wise man once told me, "Deleted code is debugged code!" So, move
the functions that are shared between merge-recursive and merge-ort from
the former to the latter, and then debug the remainder of
merge-recursive.[ch].
Joking aside, merge-ort was always intended to replace merge-recursive.
It has numerous advantages over merge-recursive (operates much faster,
can operate without a worktree or index, and fixes a number of known
bugs and suboptimal merges). Since we have now replaced all callers of
merge-recursive with equivalent functions from merge-ort, move the
shared functions from the former to the latter, and delete the remainder
of merge-recursive.[ch].
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make the code in reftable library less reliant on the service
routines it used to borrow from Git proper, to make it easier to
use by external users of the library.
* ps/reftable-sans-compat-util:
Makefile: skip reftable library for Coccinelle
reftable: decouple from Git codebase by pulling in "compat/posix.h"
git-compat-util.h: split out POSIX-emulating bits
compat/mingw: split out POSIX-related bits
reftable/basics: introduce `REFTABLE_UNUSED` annotation
reftable/basics: stop using `SWAP()` macro
reftable/stack: stop using `sleep_millisec()`
reftable/system: introduce `reftable_rand()`
reftable/reader: stop using `ARRAY_SIZE()` macro
reftable/basics: provide wrappers for big endian conversion
reftable/basics: stop using `st_mult()` in array allocators
reftable: stop using `BUG()` in trivial cases
reftable/record: don't `BUG()` in `reftable_record_cmp()`
reftable/record: stop using `BUG()` in `reftable_record_init()`
reftable/record: stop using `COPY_ARRAY()`
reftable/blocksource: stop using `xmmap()`
reftable/stack: stop using `write_in_full()`
reftable/stack: stop using `read_in_full()`
Ensure what we write in assert() does not have side effects,
and introduce ASSERT() macro to mark those that cannot be
mechanically checked for lack of side effects.
* en/assert-wo-side-effects:
treewide: replace assert() with ASSERT() in special cases
ci: add build checking for side-effects in assert() calls
git-compat-util: introduce ASSERT() macro
The `struct reftable_reader` subsystem encapsulates a table that has
been read from the disk. As such, the current name of that structure is
somewhat hard to understand as it only talks about the fact that we read
something from disk, without really giving an indicator _what_ that is.
Furthermore, this naming schema doesn't really fit well into how the
other structures are named: `reftable_merged_table`, `reftable_stack`,
`reftable_block` and `reftable_record` are all named after what they
encapsulate.
Rename the subsystem to `reftable_table`, which directly gives a hint
that the data structure is about handling the individual tables part of
the stack.
While this change results in a lot of churn, it prepares for us exposing
the APIs to third-party callers now that the reftable library is a
standalone library that can be linked against by other projects.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* ps/reftable-sans-compat-util:
Makefile: skip reftable library for Coccinelle
reftable: decouple from Git codebase by pulling in "compat/posix.h"
git-compat-util.h: split out POSIX-emulating bits
compat/mingw: split out POSIX-related bits
reftable/basics: introduce `REFTABLE_UNUSED` annotation
reftable/basics: stop using `SWAP()` macro
reftable/stack: stop using `sleep_millisec()`
reftable/system: introduce `reftable_rand()`
reftable/reader: stop using `ARRAY_SIZE()` macro
reftable/basics: provide wrappers for big endian conversion
reftable/basics: stop using `st_mult()` in array allocators
reftable: stop using `BUG()` in trivial cases
reftable/record: don't `BUG()` in `reftable_record_cmp()`
reftable/record: stop using `BUG()` in `reftable_record_init()`
reftable/record: stop using `COPY_ARRAY()`
reftable/blocksource: stop using `xmmap()`
reftable/stack: stop using `write_in_full()`
reftable/stack: stop using `read_in_full()`
Enable -Wunreachable-code for developer builds.
* jk/use-wunreachable-code-for-devs:
config.mak.dev: enable -Wunreachable-code
git-compat-util: add NOT_CONSTANT macro and use it in atfork_prepare()
run-command: use errno to check for sigfillset() error
It is a big no-no to have side-effects in an assertion, because if the
assert() is compiled out, you don't get that side-effect, leading to the
code behaving differently. That can be a large headache to debug.
We have roughly 566 assert() calls in our codebase (my grep might have
picked up things that aren't actually assert() calls, but most appeared
to be). All but 9 of them can be determined by gcc to be free of side
effects with a clever redefine of assert() provided by Bruno De Fraine
(from
https://stackoverflow.com/questions/10593492/catching-assert-with-side-effects),
who upon request has graciously placed his two-liner into the public
domain without warranty of any kind. The current 9 assert() calls
flagged by this clever redefinition of assert() appear to me to be free
of side effects as well, but are too complicated for a compiler/linker
to figure that since each assertion involves some kind of function call.
Add a CI job which will find and report these possibly problematic
assertions, and have the job suggest to the user that they replace these
with ASSERT() calls.
Example output from running:
```
ERROR: The compiler could not verify the following assert()
calls are free of side-effects. Please replace with
ASSERT() calls.
/home/newren/floss/git/diffcore-rename.c:1409
assert(!dir_rename_count || strmap_empty(dir_rename_count));
/home/newren/floss/git/merge-ort.c:1645
assert(renames->deferred[side].trivial_merges_okay &&
!strset_contains(&renames->deferred[side].target_dirs,
path));
/home/newren/floss/git/merge-ort.c:794
assert(omittable_hint ==
(!starts_with(type_short_descriptions[type], "CONFLICT") &&
!starts_with(type_short_descriptions[type], "ERROR")) ||
type == CONFLICT_DIR_RENAME_SUGGESTED);
/home/newren/floss/git/merge-recursive.c:1200
assert(!merge_remote_util(commit));
/home/newren/floss/git/object-file.c:2709
assert(would_convert_to_git_filter_fd(istate, path));
/home/newren/floss/git/parallel-checkout.c:280
assert(is_eligible_for_parallel_checkout(pc_item->ce, &pc_item->ca));
/home/newren/floss/git/scalar.c:244
assert(have_fsmonitor_support());
/home/newren/floss/git/scalar.c:254
assert(have_fsmonitor_support());
/home/newren/floss/git/sequencer.c:4968
assert(!(opts->signoff || opts->no_commit ||
opts->record_origin || should_edit(opts) ||
opts->committer_date_is_author_date ||
opts->ignore_date));
```
Note that if there are possibly problematic assertions, not necessarily
all of them will be shown in a single run, because the compiler errors
may include something like "ld: ... more undefined references to
`not_supposed_to_survive' follow" instead of listing each individually.
But in such cases, once you clean up a few that are shown in your first
run, subsequent runs will show (some of) the ones that remain, allowing
you to iteratively remove them all.
Helped-by: Bruno De Fraine <defraine@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our hope is that the number of code paths that falsely trigger
warnings with the -Wunreachable-code compilation option are small,
and they can be worked around case-by-case basis, like we just did
in the previous commit. If we need such a workaround a bit more
often, however, we may benefit from a more generic and descriptive
facility that helps document the cases we need such workarounds.
Side note: if we need the workaround all over the place, it
simply means -Wunreachable-code is not a good tool for us to
save engineering effort to catch mistakes. We are still
exploring if it helps us, so let's assume that it is not the
case.
Introduce NOT_CONSTANT() macro, with which, the developer can tell
the compiler:
Do not optimize this expression out, because, despite whatever
you are told by the system headers, this expression should *not*
be treated as a constant.
and use it as a replacement for the workaround we used that was
somewhat specific to the sigfillset case. If the compiler already
knows that the call to sigfillset() cannot fail on a particular
platform it is compiling for and declares that the if() condition
would not hold, it is plausible that the next version of the
compiler may learn that sigfillset() that never fails would not
touch errno and decide that in this sequence:
errno = 0;
sigfillset(&all)
if (errno)
die_errno("sigfillset");
the if() statement will never trigger. Marking that the value
returned by sigfillset() cannot be a constant would document our
intention better and would not break with such a new version of
compiler that is even more "clever". With the marco, the above
sequence can be rewritten:
if (NOT_CONSTANT(sigfillset(&all)))
die_errno("sigfillset");
which looks almost like other innocuous annotations we have,
e.g. UNUSED.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While we have a "hash.h" header, the actual implementation of the
subsystem is hosted by "object-file.c". This makes it harder than
necessary to find the actual implementation of the hash subsystem and
intermingles the different concerns with one another.
Split out the implementation of hash algorithms into a new, separate
"hash.c" file.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert a few unit tests to the clar framework.
* sk/unit-test-oid:
t/unit-tests: convert oidtree test to use clar test framework
t/unit-tests: convert oidmap test to use clar test framework
t/unit-tests: convert oid-array test to use clar test framework
t/unit-tests: implement clar specific oid helper functions
Adapt urlmatch-normalization test file to use clar testing framework by
using clar assertions where necessary.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapt trailer test file to use clar testing framework by using clar
assertions where necessary. Split test into individual test functions
for clarity and maintainability. Each test case now has its own
function, making it easier to isolate failures and improve test
readability.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Through git-diff(1), a single diff can be generated from a pair of blob
revisions directly. Unfortunately, there is not a mechanism to compute
batches of specific file pair diffs in a single process. Such a feature
is particularly useful on the server-side where diffing between a large
set of changes is not feasible all at once due to timeout concerns.
To facilitate this, introduce git-diff-pairs(1) which acts as a backend
passing its NUL-terminated raw diff format input from stdin through diff
machinery to produce various forms of output such as patch or raw.
The raw format was originally designed as an interchange format and
represents the contents of the diff_queued_diff list making it possible
to break the diff pipeline into separate stages. For example,
git-diff-tree(1) can be used as a frontend to compute file pairs to
queue and feed its raw output to git-diff-pairs(1) to compute patches.
With this, batches of diffs can be progressively generated without
having to recompute renames or retrieve object context. Something like
the following:
git diff-tree -r -z -M $old $new |
git diff-pairs -p -z
should generate the same output as `git diff-tree -p -M`. Furthermore,
each line of raw diff formatted input can also be individually fed to a
separate git-diff-pairs(1) process and still produce the same output.
Based-on-patch-by: Jeff King <peff@peff.net>
Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapt oidtree test script to clar framework by using clar assertions
where necessary. `cl_parse_any_oid()` ensures the hash algorithm is set
before parsing. This prevents issues from an uninitialized or invalid
hash algorithm.
Introduce 'test_oidtree__initialize` handles the to set up of the global
oidtree variable and `test_oidtree__cleanup` frees the oidtree when all
tests are completed.
With this change, `check_each` stops at the first error encountered,
making it easier to address it.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapt oidmap test script to clar framework by using clar assertions
where necessary. `cl_parse_any_oid()` ensures the hash algorithm is set
before parsing. This prevents issues from an uninitialized or invalid
hash algorithm.
Introduce 'test_oidmap__initialize` handles the to set up of the global
oidmap map with predefined key-value pairs, and `test_oidmap__cleanup`
frees the oidmap and its entries when all tests are completed.
The test loops through all entries to detect multiple errors. With this
change, it stops at the first error encountered, making it easier to
address it.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapt oid-array test script to clar framework by using clar assertions
where necessary. Remove descriptions from macros to reduce
redundancy, and move test input arrays to global scope for reuse across
multiple test functions. Introduce `test_oid_array__initialize()` to
explicitly initialize the hash algorithm.
These changes streamline the test suite, making individual tests
self-contained and reducing redundant code.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
`get_oid_arbitrary_hex()` and `init_hash_algo()` are both required for
oid-related tests to run without errors. In the current implementation,
both functions are defined and declared in the
`t/unit-tests/lib-oid.{c,h}` which is utilized by oid-related tests in
the homegrown unit tests structure.
Adapt functions in lib-oid.{c,h} to use clar. Both these functions
become available for oid-related test files implemented using the clar
testing framework, which requires them. This will be used by subsequent
commits.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Lazy-loading missing files in a blobless clone on demand is costly
as it tends to be one-blob-at-a-time. "git backfill" is introduced
to help bulk-download necessary files beforehand.
* ds/backfill:
backfill: assume --sparse when sparse-checkout is enabled
backfill: add --sparse option
backfill: add --min-batch-size=<n> option
backfill: basic functionality and tests
backfill: add builtin boilerplate
A couple of our tests require knowledge around where to find the
project's source directory in order to locate files required for the
test itself. Until now we have been wiring these up ad-hoc via new,
specialized variables catered to the specific usecase. This is quite
awkward though, as every test that potentially needs to locate paths
relative to the source directory needs to grow another variable.
Introduce a new "GIT_SOURCE_DIR" variable into GIT-BUILD-OPTIONS to stop
this proliferation. Remove existing variables that can be derived from
it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The reftable library does not use any of the common helpers that the Git
project has. Consequently, most of the rules that we have in Coccinelle
do not apply to the library at all and may even generate false positives
when a pattern can be converted to use a Git helper function.
Exclude reftable library sources from being checked by Coccinelle to
avoid such false positives.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
All the documentation .txt files have been renamed to .adoc to help
content aware editors.
* bc/doc-adoc-not-txt:
Remove obsolete ".txt" extensions for AsciiDoc files
doc: use .adoc extension for AsciiDoc files
gitattributes: mark AsciiDoc files as LF-only
editorconfig: add .adoc extension
doc: update gitignore for .adoc extension
Back in 728b9ac0c3 (Makefile(s): avoid recipe prefix in conditional
statements, 2024-04-08), we prepared our Makefiles for a forthcoming
change in upstream Make that would ban the recipe prefix within a
conditional statement by replacing tabs (the prefix) with eight spaces.
In b9d6f64393 (compat/zlib: allow use of zlib-ng as backend,
2025-01-28), a handful of recipe prefix characters were introduced in a
conditional statement ('ifdef ZLIB_NG'), causing 'make' to fail on my
system, which uses GNU Make 4.4.90.
Remove the recipe prefix characters by replacing them with the same
script as is mentioned in 728b9ac0c3.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Foreign language interface for Rust into our code base has been added.
* js/libgit-rust:
libgit: add higher-level libgit crate
libgit-sys: also export some config_set functions
libgit-sys: introduce Rust wrapper for libgit.a
common-main: split init and exit code into new files
"git pack-objects" and its wrapper "git repack" learned an option
to use an alternative path-hash function to improve delta-base
selection to produce a packfile with deeper history than window
size.
* ds/name-hash-tweaks:
pack-objects: prevent name hash version change
test-tool: add helper for name-hash values
p5313: add size comparison test
pack-objects: add GIT_TEST_NAME_HASH_VERSION
repack: add --name-hash-version option
pack-objects: add --name-hash-version option
pack-objects: create new name-hash function version
Convert a handful of unit tests to work with the clar framework.
* sk/unit-tests-0130:
t/unit-tests: convert strcmp-offset test to use clar test framework
t/unit-tests: convert strbuf test to use clar test framework
t/unit-tests: adapt example decorate test to use clar test framework
t/unit-tests: convert hashmap test to use clar test framework
The code paths to interact with zlib has been cleaned up in
preparation for building with zlib-ng.
* ps/zlib-ng:
ci: make "linux-musl" job use zlib-ng
ci: switch linux-musl to use Meson
compat/zlib: allow use of zlib-ng as backend
git-zlib: cast away potential constness of `next_in` pointer
compat/zlib: provide stubs for `deflateSetHeader()`
compat/zlib: provide `deflateBound()` shim centrally
git-compat-util: move include of "compat/zlib.h" into "git-zlib.h"
compat: introduce new "zlib.h" header
git-compat-util: drop `z_const` define
compat: drop `uncompress2()` compatibility shim
In anticipation of implementing 'git backfill', populate the necessary files
with the boilerplate of a new builtin. Mark the builtin as experimental at
this time, allowing breaking changes in the near future, if necessary.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Following the procedure we established to introduce breaking
changes for Git 3.0, allow an early opt-in for removing support of
$GIT_DIR/branches/ and $GIT_DIR/remotes/ directories to configure
remotes.
* ps/3.0-remote-deprecation:
remote: announce removal of "branches/" and "remotes/"
builtin/pack-redundant: remove subcommand with breaking changes
ci: repurpose "linux-gcc" job for deprecations
ci: merge linux-gcc-default into linux-gcc
Makefile: wire up build option for deprecated features
Adapt strcmp-offset test script to clar framework by using clar
assertions where necessary. Introduce `test_strcmp_offset__empty()` to
verify `check_strcmp_offset()` behavior when both input strings are
empty. This ensures the function correctly handles edge cases and
returns expected values.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapt strbuf test script to clar framework by using clar assertions
where necessary.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce `test_example_decorate__initialize()` to explicitly set up
object IDs and retrieve corresponding objects before tests run. This
ensures a consistent and predictable test state without relying on data
from previous tests.
Add `test_example_decorate__cleanup()` to clear decorations after each
test, preventing interference between tests and ensuring each runs in
isolation.
Adapt example decorate test script to clar framework by using clar
assertions where necessary. Previously, tests relied on data written by
earlier tests, leading to unintended dependencies between them. This
explicitly initializes the necessary state within
`test_example_decorate__readd`, ensuring it does not depend on prior
test executions.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Adapts hashmap test script to clar framework by using clar assertions
where necessary.
Mentored-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Seyi Kuforiji <kuforiji98@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The C functions exported by libgit-sys do not provide an idiomatic Rust
interface. To make it easier to use these functions via Rust, add a
higher-level "libgit" crate, that wraps the lower-level configset API
with an interface that is more Rust-y.
This combination of $X and $X-sys crates is a common pattern for FFI in
Rust, as documented in "The Cargo Book" [1].
[1] https://doc.rust-lang.org/cargo/reference/build-scripts.html#-sys-packages
Co-authored-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce a new API to visit objects in batches based on a common
path, or by type.
* ds/path-walk-1:
path-walk: drop redundant parse_tree() call
path-walk: reorder object visits
path-walk: mark trees and blobs as UNINTERESTING
path-walk: visit tags and cached objects
path-walk: allow consumer to specify object types
t6601: add helper for testing path-walk API
test-lib-functions: add test_cmp_sorted
path-walk: introduce an object walk by path
Introduce libgit-sys, a Rust wrapper crate that allows Rust code to call
functions in libgit.a. This initial patch defines build rules and an
interface that exposes user agent string getter functions as a proof of
concept. This library can be tested with `cargo test`. In later commits,
a higher-level library containing a more Rust-friendly interface will be
added at `contrib/libgit-rs`.
Symbols in libgit can collide with symbols from other libraries such as
libgit2. We avoid this by first exposing library symbols in
public_symbol_export.[ch]. These symbols are prepended with "libgit_" to
avoid collisions and set to visible using a visibility pragma. In
build.rs, Rust builds contrib/libgit-rs/libgit-sys/libgitpub.a, which also
contains libgit.a and other dependent libraries, with
-fvisibility=hidden to hide all symbols within those libraries that
haven't been exposed with a visibility pragma.
Co-authored-by: Kyle Lippincott <spectral@google.com>
Co-authored-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Kyle Lippincott <spectral@google.com>
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Currently, object files in libgit.a reference common_exit(), which is
contained in common-main.o. However, common-main.o also includes main(),
which references cmd_main() in git.o, which in turn depends on all the
builtin/*.o objects.
We would like to allow external users to link libgit.a without needing
to include so many extra objects. Enable this by splitting common_exit()
and check_bug_if_BUG() into a new file common-exit.c, and add
common-exit.o to LIB_OBJS so that these are included in libgit.a.
This split has previously been proposed ([1], [2]) to support fuzz tests
and unit tests by avoiding conflicting definitions for main(). However,
both of those issues were resolved by other methods of avoiding symbol
conflicts. Now we are trying to make libgit.a more self-contained, so
hopefully we can revisit this approach.
Additionally, move the initialization code out of main() into a new
init_git() function in its own file. Include this in libgit.a as well,
so that external users can share our setup code without calling our
main().
[1] https://lore.kernel.org/git/Yp+wjCPhqieTku3X@google.com/
[2] https://lore.kernel.org/git/20230517-unit-tests-v2-v2-1-21b5b60f4b32@google.com/
Signed-off-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The zlib-ng library is a hard fork of the old and venerable zlib
library. It describes itself as zlib replacement with optimizations for
"next generation" systems. As such, it contains several implementations
of central algorithms using for example SSE2, AVX2 and other vectorized
CPU intrinsics that supposedly speed up in- and deflating data.
And indeed, compiling Git against zlib-ng leads to a significant speedup
when reading objects. The following benchmark uses git-cat-file(1) with
`--batch --batch-all-objects` in the Git repository:
Benchmark 1: zlib
Time (mean ± σ): 52.085 s ± 0.141 s [User: 51.500 s, System: 0.456 s]
Range (min … max): 52.004 s … 52.335 s 5 runs
Benchmark 2: zlib-ng
Time (mean ± σ): 40.324 s ± 0.134 s [User: 39.731 s, System: 0.490 s]
Range (min … max): 40.135 s … 40.484 s 5 runs
Summary
zlib-ng ran
1.29 ± 0.01 times faster than zlib
So we're looking at a ~25% speedup compared to zlib. This is of course
an extreme example, as it makes us read through all objects in the
repository. But regardless, it should be possible to see some sort of
speedup in most commands that end up accessing the object database.
The zlib-ng library provides a compatibility layer that makes it a
proper drop-in replacement for zlib: nothing needs to change in the
build system to support it. Unfortunately though, this mode isn't easy
to use on most systems because distributions do not allow you to install
zlib-ng in that way, as that would mean that the zlib library would be
globally replaced. Instead, many distributions provide a package that
installs zlib-ng without the compatibility layer. This version does
provide effectively the same APIs like zlib does, but all of the symbols
are prefixed with `zng_` to avoid symbol collisions.
Implement a new build option that allows us to link against zlib-ng
directly. If set, we redefine zlib symbols so that we use the `zng_`
prefixed versions thereof provided by that library. Like this, it
becomes possible to install both zlib and zlib-ng (without the compat
layer) and then pick whichever library one wants to link against for
Git.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our compat library has an implementation of zlib's `uncompress2()`
function that gets used when linking against an old version of zlib
that doesn't yet have it. The last user of `uncompress2()` got removed
in 15a60b747e (reftable/block: open-code call to `uncompress2()`,
2024-04-08), so the compatibility code is not required anymore. Drop it.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move a few more unit tests to the clar test framework.
* sk/unit-tests:
t/unit-tests: convert reftable tree test to use clar test framework
t/unit-tests: adapt priority queue test to use clar test framework
t/unit-tests: convert mem-pool test to use clar test framework
t/unit-tests: handle dashes in test suite filenames
Add a new test-tool helper, name-hash, to output the value of the
name-hash algorithms for the input list of strings, one per line.
Since the name-hash values can be stored in the .bitmap files, it is
important that these hash functions do not change across Git versions.
Add a simple test to t5310-pack-bitmaps.sh to provide some testing of
the current values. Due to how these functions are implemented, it would
be difficult to change them without disturbing these values. The paths
used for this test are carefully selected to demonstrate some of the
behavior differences of the two current name hash versions, including
which conditions will cause them to collide.
Create a performance test that uses test_size to demonstrate how
collisions occur for these hash algorithms. This test helps inform
someone as to the behavior of the name-hash algorithms for their repo
based on the paths at HEAD.
My copy of the Git repository shows modest statistics around the
collisions of the default name-hash algorithm:
Test this tree
--------------------------------------------------
5314.1: paths at head 4.5K
5314.2: distinct hash value: v1 4.1K
5314.3: maximum multiplicity: v1 13
5314.4: distinct hash value: v2 4.2K
5314.5: maximum multiplicity: v2 9
Here, the maximum collision multiplicity is 13, but around 10% of paths
have a collision with another path.
In a more interesting example, the microsoft/fluentui [1] repo had these
statistics at time of committing:
Test this tree
--------------------------------------------------
5314.1: paths at head 19.5K
5314.2: distinct hash value: v1 8.2K
5314.3: maximum multiplicity: v1 279
5314.4: distinct hash value: v2 17.8K
5314.5: maximum multiplicity: v2 44
[1] https://github.com/microsoft/fluentui
That demonstrates that of the nearly twenty thousand path names, they
are assigned around eight thousand distinct values. 279 paths are
assigned to a single value, leading the packing algorithm to sort
objects from those paths together, by size.
With the v2 name hash function, the maximum multiplicity lowers to 44,
leaving some room for further improvement.
In a more extreme example, an internal monorepo had a much worse
collision rate:
Test this tree
--------------------------------------------------
5314.1: paths at head 227.3K
5314.2: distinct hash value: v1 72.3K
5314.3: maximum multiplicity: v1 14.4K
5314.4: distinct hash value: v2 166.5K
5314.5: maximum multiplicity: v2 138
Here, we can see that the v2 name hash function provides somem
improvements, but there are still a number of collisions that could lead
to repacking problems at this scale.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The git-pack-redundant(1) subcommand has been castrated to require
the "--i-still-use-this" option to do anything since 4406522b
(pack-redundant: escalate deprecation warning to an error,
2023-03-23), which appeared in Git 2.41 and was announced for
removal with 53a92c9552 (Documentation/BreakingChanges: announce
removal of git-pack-redundant(1), 2024-09-02). Stop compiling the
subcommand in case the `WITH_BREAKING_CHANGES` build flag is set.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
With 57ec9254eb (docs: introduce document to announce breaking changes,
2024-06-14), we have introduced a new document that tracks upcoming
breaking changes in the Git project. In 2454970930 (BreakingChanges:
early adopter option, 2024-10-11) we have amended the document a bit to
mention that any introduced breaking changes must be accompanied by
logic that allows us to enable the breaking change at compile-time.
While we already have two breaking changes lined up, neither of them has
such a switch because they predate those instructions.
Introduce the proposed `WITH_BREAKING_CHANGES` preprocessor macro and
wire it up with both our Makefiles and Meson. This does not yet wire up
the build flag for existing deprecations.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We presently use the ".txt" extension for our AsciiDoc files. While not
wrong, most editors do not associate this extension with AsciiDoc,
meaning that contributors don't get automatic editor functionality that
could be useful, such as syntax highlighting and prose linting.
It is much more common to use the ".adoc" extension for AsciiDoc files,
since this helps editors automatically detect files and also allows
various forges to provide rich (HTML-like) rendering. Let's do that
here, renaming all of the files and updating the includes where
relevant. Adjust the various build scripts and makefiles to use the new
extension as well.
Note that this should not result in any user-visible changes to the
documentation.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
