The pseudo-merge reachability bitmap to help more efficient storage
of the reachability bitmap in a repository with too many refs has
been added.
* tb/pseudo-merge-reachability-bitmap: (26 commits)
pack-bitmap.c: ensure pseudo-merge offset reads are bounded
Documentation/technical/bitmap-format.txt: add missing position table
t/perf: implement performance tests for pseudo-merge bitmaps
pseudo-merge: implement support for finding existing merges
ewah: `bitmap_equals_ewah()`
pack-bitmap: extra trace2 information
pack-bitmap.c: use pseudo-merges during traversal
t/test-lib-functions.sh: support `--notick` in `test_commit_bulk()`
pack-bitmap: implement test helpers for pseudo-merge
ewah: implement `ewah_bitmap_popcount()`
pseudo-merge: implement support for reading pseudo-merge commits
pack-bitmap.c: read pseudo-merge extension
pseudo-merge: scaffolding for reads
pack-bitmap: extract `read_bitmap()` function
pack-bitmap-write.c: write pseudo-merge table
pseudo-merge: implement support for selecting pseudo-merge commits
config: introduce `git_config_double()`
pack-bitmap: make `bitmap_writer_push_bitmapped_commit()` public
pack-bitmap: implement `bitmap_writer_has_bitmapped_object_id()`
pack-bitmap-write: support storing pseudo-merge commits
...
The "--heads" option of "ls-remote" and "show-ref" has been been
deprecated; "--branches" replaces "--heads".
* jc/heads-are-branches:
show-ref: introduce --branches and deprecate --heads
ls-remote: introduce --branches and deprecate --heads
refs: call branches branches
The structure of the document that records longer-term project
decisions to deprecate/remove/update various behaviour has been
outlined.
* ps/document-breaking-changes:
BreakingChanges: document that we do not plan to deprecate git-checkout
BreakingChanges: document removal of grafting
BreakingChanges: document upcoming change from "sha1" to "sha256"
docs: introduce document to announce breaking changes
When the user adds to "git rebase -i" instruction to "pick" a merge
commit, the error experience is not pleasant. Such an error is now
caught earlier in the process that parses the todo list.
* pw/rebase-i-error-message:
rebase -i: improve error message when picking merge
rebase -i: pass struct replay_opts to parse_insn_line()
Setting core.abbrev too early before the repository set-up
(typically in "git clone") caused segfault, which as been
corrected.
* ps/abbrev-length-before-setup-fix:
object-name: don't try to abbreviate to lengths greater than hexsz
parse-options-cb: stop clamping "--abbrev=" to hash length
config: fix segfault when parsing "core.abbrev" without repo
"git format-patch --interdiff" for multi-patch series learned to
turn on cover letters automatically (unless told never to enable
cover letter with "--no-cover-letter" and such).
* rj/format-patch-auto-cover-with-interdiff:
format-patch: assume --cover-letter for diff in multi-patch series
t4014: cleanups in a few tests
"git update-ref --stdin" learned to handle transactional updates of
symbolic-refs.
* kn/update-ref-symref:
update-ref: add support for 'symref-update' command
reftable: pick either 'oid' or 'target' for new updates
update-ref: add support for 'symref-create' command
update-ref: add support for 'symref-delete' command
update-ref: add support for 'symref-verify' command
refs: specify error for regular refs with `old_target`
refs: create and use `ref_update_expects_existing_old_ref()`
Assorted fixes to multi-pack-index code paths.
* tb/multi-pack-reuse-fix:
pack-revindex.c: guard against out-of-bounds pack lookups
pack-bitmap.c: avoid uninitialized `pack_int_id` during reuse
midx-write.c: do not read existing MIDX with `packs_to_include`
To help developers, the build procedure now allows builders to use
CFLAGS_APPEND to specify additional CFLAGS.
* ps/make-append-to-cflags:
Makefile: add ability to append to CFLAGS and LDFLAGS
"git diff --exit-code --ext-diff" learned to take the exit status
of the external diff driver into account when deciding the exit
status of the overall "git diff" invocation when configured to do
so.
* rs/diff-exit-code-with-external-diff:
diff: let external diffs report that changes are uninteresting
userdiff: add and use struct external_diff
t4020: test exit code with external diffs
A leak in "git imap-send" that somehow escapes LSan has been
plugged.
* jk/imap-send-plug-all-msgs-leak:
imap-send: free all_msgs strbuf in "out" label
Building with "-Werror -Wwrite-strings" is now supported.
* ps/no-writable-strings: (27 commits)
config.mak.dev: enable `-Wwrite-strings` warning
builtin/merge: always store allocated strings in `pull_twohead`
builtin/rebase: always store allocated string in `options.strategy`
builtin/rebase: do not assign default backend to non-constant field
imap-send: fix leaking memory in `imap_server_conf`
imap-send: drop global `imap_server_conf` variable
mailmap: always store allocated strings in mailmap blob
revision: always store allocated strings in output encoding
remote-curl: avoid assigning string constant to non-const variable
send-pack: always allocate receive status
parse-options: cast long name for OPTION_ALIAS
http: do not assign string constant to non-const field
compat/win32: fix const-correctness with string constants
pretty: add casts for decoration option pointers
object-file: make `buf` parameter of `index_mem()` a constant
object-file: mark cached object buffers as const
ident: add casts for fallback name and GECOS
entry: refactor how we remove items for delayed checkouts
line-log: always allocate the output prefix
line-log: stop assigning string constant to file parent buffer
...
"git am" has a safety feature to prevent it from starting a new
session when there already is a session going. It reliably
triggers when a mbox is given on the command line, but it has to
rely on the tty-ness of the standard input. Add an explicit way to
opt out of this safety with a command line option.
* jk/am-retry:
test-terminal: drop stdin handling
am: add explicit "--retry" option
Varargs functions that are unannotated as printf-like or execl-like
have been annotated as such.
* jc/varargs-attributes:
__attribute__: add a few missing format attributes
__attribute__: mark some functions with LAST_ARG_MUST_BE_NULL
__attribute__: remove redundant attribute declaration for git_die_config()
__attribute__: trace2_region_enter_printf() is like "printf"
A new command has been added to migrate a repository that uses the
files backend for its ref storage to use the reftable backend, with
limitations.
* ps/ref-storage-migration:
builtin/refs: new command to migrate ref storage formats
refs: implement logic to migrate between ref storage formats
refs: implement removal of ref storages
worktree: don't store main worktree twice
reftable: inline `merged_table_release()`
refs/files: fix NULL pointer deref when releasing ref store
refs/files: extract function to iterate through root refs
refs/files: refactor `add_pseudoref_and_head_entries()`
refs: allow to skip creation of reflog entries
refs: pass storage format to `ref_store_init()` explicitly
refs: convert ref storage format to an enum
setup: unset ref storage when reinitializing repository version
"make check-docs" noticed problems and reported to its output but
failed to signal its findings with its exit status, which has been
corrected.
* ps/check-docs-fix:
ci/test-documentation: work around SyntaxWarning in Python 3.12
gitlab-ci: add job to run `make check-docs`
Documentation/lint-manpages: bubble up errors
Makefile: extract script to lint missing/extraneous manpages
Upon expiration event, the credential subsystem forgot to clear
in-core authentication material other than password (whose support
was added recently), which has been corrected.
* ap/credential-clear-fix:
credential: clear expired c->credential, unify secret clearing
The inter/range-diff output has been moved to the end of the patch
when format-patch adds it to a single patch, instead of writing it
before the patch text, to be consistent with what is done for a
cover letter for a multi-patch series.
* jc/format-patch-with-range-diff:
format-patch: move range/inter diff at the end of a single patch output
show_log: factor out interdiff/range-diff generation
After reading the pseudo-merge extension's metadata table, we allocate
an array to store information about each pseudo-merge, including its
byte offset within the .bitmap file itself.
This is done like so:
pseudo_merge_ofs = index_end - 24 -
(index->pseudo_merges.nr * sizeof(uint64_t));
for (i = 0; i < index->pseudo_merges.nr; i++) {
index->pseudo_merges.v[i].at = get_be64(pseudo_merge_ofs);
pseudo_merge_ofs += sizeof(uint64_t);
}
But if the pseudo-merge table is corrupt, we'll keep calling get_be64()
past the end of the pseudo-merge extension, potentially reading off the
end of the mmap'd region.
Prevent this by ensuring that we have at least `table_size - 24` many
bytes available to read (adding 24 to the left-hand side of our
inequality to account for the length of the metadata component).
This is sufficient to prevent us from reading off the end of the
pseudo-merge extension, and ensures that all of the get_be64() calls
below are in bounds.
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While investigating a benign Coverity warning on the new pseudo-merge
implementation, I was struggling to understand the (paraphrased) below:
ofs = index_end - 24 - (index->pseudo_merges.nr * sizeof(uint64_t));
for (i = 0; i < index->pseudo_merges.nr; i++) {
index->pseudo_merges.v[i].at = get_be64(ofs);
ofs += sizeof(uint64_t);
}
, in pack-bitmap.c::load_bitmap_header(). Looking at the documentation,
the diagram describing the on-disk format (prior to this patch)
suggested that the optional extended lookup table immediately preceded
the trailing metadata portion.
If that were the case, that would make the above code from
load_bitmap_header() incorrect, as we'd be blindly reading into the
extended offset table.
But later on in the documentation there is a description of the
pseudo-merge position table as immediately preceding the trailing
metadata portion of the extension. And indeed, we do write the position
table in pack-bitmap-write.c:
/* write positions for all pseudo merges */
for (i = 0; i < writer->pseudo_merges_nr; i++)
hashwrite_be64(f, pseudo_merge_ofs[i]);
hashwrite_be32(f, writer->pseudo_merges_nr);
hashwrite_be32(f, kh_size(writer->pseudo_merge_commits));
hashwrite_be64(f, table_start - start);
hashwrite_be64(f, hashfile_total(f) - start + sizeof(uint64_t));
So this is purely a case of the diagram being out of sync with the
textual description and actual implementation of the format
specification.
Add the missing component back to the format diagram to avoid further
confusion in this area.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The git-checkout(1) command is seen by many as hard to understand
because it connects two somewhat unrelated features: switching between
branches and restoring worktree files from arbitrary revisions. In 2019,
we thus implemented two new commands git-switch(1) and git-restore(1) to
split out these separate concerns into standalone functions.
This "replacement" of git-checkout(1) has repeatedly triggered concerns
for our userbase that git-checkout(1) will eventually go away. This is
not the case though: the use of that command is still widespread, and it
is not expected that this will change anytime soon.
Document that all three commands will remain for the foreseeable future.
This decision may be revisited in case we ever figure out that most
everyone has given up on any of the commands.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The grafting mechanism for objects has been deprecated in e650d0643b
(docs: mark info/grafts as outdated, 2014-03-05), which is more than a
decade ago. The mechanism can lead to hard-to-debug issues and has a
superior replacement with replace refs.
Follow through with the deprecation and mark grafts for removal in Git
3.0.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Starting with 8e42eb0e9a (doc: sha256 is no longer experimental,
2023-07-31), the "sha256" object format is no longer considered to be
experimental. Furthermore, the SHA-1 hash function is actively
recommended against by for example NIST and FIPS 140-2, and attacks
against it are becoming more practical both due to new weaknesses
(SHAppening, SHAttered, Shambles) and due to the ever-increasing
computing power. It is only a matter of time before it can be considered
to be broken completely.
Let's plan for this event by being active instead of waiting for it to
happend and announce that the default object format is going to change
from "sha1" to "sha256" with Git 3.0.
All major Git implementations (libgit2, JGit, go-git) support the
"sha256" object format and are thus prepared for this change. The most
important missing piece in the puzzle is support in forges. But while
GitLab recently gained experimental support for the "sha256" object
format though, to the best of my knowledge GitHub doesn't support it
yet. Ideally, announcing this upcoming change will encourage forges to
start building that support.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Over time, Git has grown quite a lot. With this evolution, many ideas
that were sensible at the time they were introduced are not anymore and
are thus considered to be deprecated. And while some deprecations may be
noted in manpages, most of them are actually deprecated in the "hive
mind" of the Git community, only.
Introduce a new document that tracks such breaking changes, but also
deprecations which we are not willing to go through with, to address
this issue. This document serves multiple purposes:
- It is a way to facilitate discussion around proposed deprecations.
- It allows users to learn about deprecations and speak up in case
they have good reasons why a certain feature should not be
deprecated.
- It states intent and documents where the Git project wants to go,
both in the case where we want to deprecate, but also in the case
where we don't want to deprecate a specific feature.
The document is _not_ intended to cast every single discussion into
stone. It is supposed to be a living document that may change over time
when there are good reasons for it to change.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This fixes a bug that was introduced by 368d19b0b7 (commit-graph:
refactor compute_topological_levels(), 2023-03-20): Previously, the
progress indicator was updated from `i + 1` where `i` is the loop
variable of the enclosing `for` loop. After this patch, the update used
`info->progress_cnt + 1` instead, however, unlike `i`, the
`progress_cnt` attribute was not incremented. Let's increment it.
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
[jc: squashed in a test update from Patrick Steinhardt]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A test helper that essentially is unit tests on the "decorate"
logic has been rewritten using the unit-tests framework.
* gt/decorate-unit-test:
t/: migrate helper/test-example-decorate to the unit testing framework
Many memory leaks in the sparse-checkout code paths have been
plugged.
* jk/sparse-leakfix:
sparse-checkout: free duplicate hashmap entries
sparse-checkout: free string list after displaying
sparse-checkout: free pattern list in sparse_checkout_list()
sparse-checkout: free sparse_filename after use
sparse-checkout: refactor temporary sparse_checkout_patterns
sparse-checkout: always free "line" strbuf after reading input
sparse-checkout: reuse --stdin buffer when reading patterns
dir.c: always copy input to add_pattern()
dir.c: free removed sparse-pattern hashmap entries
sparse-checkout: clear patterns when init() sees existing sparse file
dir.c: free strings in sparse cone pattern hashmaps
sparse-checkout: pass string literals directly to add_pattern()
sparse-checkout: free string list in write_cone_to_file()
An overly large ".gitignore" files are now rejected silently.
* jk/cap-exclude-file-size:
dir.c: reduce max pattern file size to 100MB
dir.c: skip .gitignore, etc larger than INT_MAX
The safe.directory configuration knob has been updated to
optionally allow leading path matches.
* jc/safe-directory-leading-path:
safe.directory: allow "lead/ing/path/*" match
A pair of test helpers that essentially are unit tests on hash
algorithms have been rewritten using the unit-tests framework.
* gt/t-hash-unit-test:
t/: migrate helper/test-{sha1, sha256} to unit-tests/t-hash
strbuf: introduce strbuf_addstrings() to repeatedly add a string
Basic unit tests for reftable have been reimplemented under the
unit test framework.
* cp/reftable-unit-test:
t: improve the test-case for parse_names()
t: add test for put_be16()
t: move tests from reftable/record_test.c to the new unit test
t: move tests from reftable/stack_test.c to the new unit test
t: move reftable/basics_test.c to the unit testing framework
A new test was added to ensure git commands that are designed to
run outside repositories do work.
* jc/t1517-more:
imap-send: minimum leakfix
t1517: more coverage for commands that work without repository
helper/test-oidtree.c along with t0069-oidtree.sh test the oidtree.h
library, which is a wrapper around crit-bit tree. Migrate them to
the unit testing framework for better debugging and runtime
performance. Along with the migration, add an extra check for
oidtree_each() test, which showcases how multiple expected matches can
be given to check_each() helper.
To achieve this, introduce a new library called 'lib-oid.h'
exclusively for the unit tests to use. It currently mainly includes
utility to generate object_id from an arbitrary hex string
(i.e. '12a' -> '12a0000000000000000000000000000000000000'). This also
handles the hash algo selection based on GIT_TEST_DEFAULT_HASH.
This library will also be helpful when we port other unit tests such
as oid-array, oidset etc.
Helped-by: Junio C Hamano <gitster@pobox.com>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Kaartic Sivaraam <kaartic.sivaraam@gmail.com>
Signed-off-by: Ghanshyam Thakkar <shyamthakkar001@gmail.com>
[jc: small fixlets squashed in]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When given a length that equals the current hash algorithm's hex size,
then `repo_find_unique_abbrev_r()` exits early without trying to find an
abbreviation. This is only sensible because there is nothing to
abbreviate in the first place, so searching through objects to find a
unique prefix would be a waste of compute.
What we don't handle though is the case where the user passes a length
greater than the hash length. This is fine in practice as we still
compute the correct result. But at the very least, this is a waste of
resources as we try to abbreviate a value that cannot be abbreviated,
which causes us to hit the object database.
Start to explicitly handle values larger than hexsz to avoid this
performance penalty, which leads to a measureable speedup. The following
benchmark has been executed in linux.git:
Benchmark 1: git -c core.abbrev=9000 log --abbrev-commit (revision = HEAD~)
Time (mean ± σ): 12.812 s ± 0.040 s [User: 12.225 s, System: 0.554 s]
Range (min … max): 12.723 s … 12.857 s 10 runs
Benchmark 2: git -c core.abbrev=9000 log --abbrev-commit (revision = HEAD)
Time (mean ± σ): 11.095 s ± 0.029 s [User: 10.546 s, System: 0.521 s]
Range (min … max): 11.037 s … 11.122 s 10 runs
Summary
git -c core.abbrev=9000 log --abbrev-commit HEAD (revision = HEAD) ran
1.15 ± 0.00 times faster than git -c core.abbrev=9000 log --abbrev-commit HEAD (revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `OPT__ABBREV()` option allows the user to specify the length that
object hashes shall be abbreviated to. This length needs to be in the
range of `(MIN_ABBREV, the_hash_algo->hexsz)`, which is why we clamp the
value as required. While this makes sense in the case of `MIN_ABBREV`,
it is unnecessary for the upper boundary as the value is eventually
passed down to `repo_find_unnique_abbrev_r()`, which handles values
larger than the current hash length just fine.
In the preceding commit, we have changed parsing of the "core.abbrev"
config to stop clamping to the upper boundary. Let's do the same here so
that the code becomes simpler, we are consistent with how we treat the
"core.abbrev" config and so that we stop depending on `the_repository`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "core.abbrev" config allows the user to specify the minimum length
when abbreviating object hashes. Next to the values "auto" and "no",
this config also accepts a concrete length that needs to be bigger or
equal to the minimum length and smaller or equal to the hash algorithm's
hex length. While the former condition is trivial, the latter depends on
the object format used by the current repository. It is thus a variable
upper boundary that may either be 40 (SHA-1) or 64 (SHA-256).
This has two major downsides. First, the user that specifies this config
must be aware of the object hashes that its repository use. If they want
to configure the value globally, then they cannot pick any value in the
range `[41, 64]` if they have any repository that uses SHA-1. If they
did, Git would error out when parsing the config.
Second, and more importantly, parsing "core.abbrev" crashes when outside
of a Git repository because we dereference `the_hash_algo` to figure out
its hex length. Starting with c8aed5e8da (repository: stop setting SHA1
as the default object hash, 2024-05-07) though, we stopped initializing
`the_hash_algo` outside of Git repositories.
Fix both of these issues by not making it an error anymore when the
given length exceeds the hash length. Instead, leave the abbreviated
length intact. `repo_find_unique_abbrev_r()` handles this just fine
except for a performance penalty which we will fix in a subsequent
commit.
Reported-by: Kyle Lippincott <spectral@google.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are some usecases where we may want to append CFLAGS to the
default CFLAGS set by Git. This could for example be to enable or
disable specific compiler warnings or to change the optimization level
that code is compiled with. This cannot be done without overriding the
complete CFLAGS value though and thus requires the user to redeclare the
complete defaults used by Git.
Introduce a new variable `CFLAGS_APPEND` that gets appended to the
default value of `CFLAGS`. As compiler options are last-one-wins, this
fulfills both of the usecases mentioned above. It's also common practice
across many other projects to have such a variable.
While at it, also introduce a matching `LDFLAGS_APPEND` variable. While
there isn't really any need for this variable as there are no default
`LDFLAGS`, users may expect this variable to exist, as well.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function midx_key_to_pack_pos() is a helper function used by
midx_to_pack_pos() and midx_pair_to_pack_pos() to translate a (pack,
offset) tuple into a position into the MIDX pseudo-pack order.
Ensure that the pack ID given to midx_pair_to_pack_pos() is bounded by
the number of packs within the MIDX to prevent, for instance,
uninitialized memory from being used as a pack ID.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When performing multi-pack reuse, reuse_partial_packfile_from_bitmap()
is responsible for generating an array of bitmapped_pack structs from
which to perform reuse.
In the multi-pack case, we loop over the MIDXs packs and copy the result
of calling `nth_bitmapped_pack()` to construct the list of reusable
paths.
But we may also want to do pack-reuse over a single pack, either because
we only had one pack to perform reuse over (in the case of single-pack
bitmaps), or because we explicitly asked to do single pack reuse even
with a MIDX[^1].
When this is the case, the array we generate of reusable packs contains
only a single element, which is either (a) the pack attached to the
single-pack bitmap, or (b) the MIDX's preferred pack.
In 795006fff4 (pack-bitmap: gracefully handle missing BTMP chunks,
2024-04-15), we refactored the reuse_partial_packfile_from_bitmap()
function and stopped assigning the pack_int_id field when reusing only
the MIDX's preferred pack. This results in an uninitialized read down in
try_partial_reuse() like so:
==7474==WARNING: MemorySanitizer: use-of-uninitialized-value
#0 0x55c5cd191dde in try_partial_reuse pack-bitmap.c:1887:8
#1 0x55c5cd191dde in reuse_partial_packfile_from_bitmap_1 pack-bitmap.c:2001:8
#2 0x55c5cd191dde in reuse_partial_packfile_from_bitmap pack-bitmap.c:2105:3
#3 0x55c5cce0bd0e in get_object_list_from_bitmap builtin/pack-objects.c:4043:3
#4 0x55c5cce0bd0e in get_object_list builtin/pack-objects.c:4156:27
#5 0x55c5cce0bd0e in cmd_pack_objects builtin/pack-objects.c:4596:3
#6 0x55c5ccc8fac8 in run_builtin git.c:474:11
which happens when try_partial_reuse() tries to call
midx_pair_to_pack_pos() when it tries to reject cross-pack deltas.
Avoid the uninitialized read by ensuring that the pack_int_id field is
set in the single-pack reuse case by setting it to either the MIDX
preferred pack's pack_int_id, or '-1', in the case of single-pack
bitmaps. In the latter case, we never read the pack_int_id field, so
the choice of '-1' is intentional as a "garbage in, garbage out"
measure.
Guard against further regressions in this area by adding a test which
ensures that we do not throw out deltas from the preferred pack as
"cross-pack" due to an uninitialized pack_int_id.
[^1]: This can happen for a couple of reasons, either because the
repository is configured with 'pack.allowPackReuse=(true|single)', or
because the MIDX was generated prior to the introduction of the BTMP
chunk, which contains information necessary to perform multi-pack
reuse.
Reported-by: Kyle Lippincott <spectral@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit d6a8c58675 (midx-write.c: support reading an existing MIDX with
`packs_to_include`, 2024-05-29) changed the MIDX generation machinery to
support reading from an existing MIDX when writing a new one.
Unfortunately, the rest of the MIDX generation machinery is not prepared
to deal with such a change. For instance, the function responsible for
adding to the object ID fanout table from a MIDX source
(midx_fanout_add_midx_fanout()) will gladly add objects from an existing
MIDX for some fanout level regardless of whether or not those objects
came from packs that are to be included in the subsequent MIDX write.
This results in broken pseudo-pack object order (leading to incorrect
object traversal results) and segmentation faults, like so (generated by
running the added test prior to the changes in midx-write.c):
#0 0x000055ee31393f47 in midx_pack_order (ctx=0x7ffdde205c70) at midx-write.c:590
#1 0x000055ee31395a69 in write_midx_internal (object_dir=0x55ee32570440 ".git/objects",
packs_to_include=0x7ffdde205e20, packs_to_drop=0x0, preferred_pack_name=0x0,
refs_snapshot=0x0, flags=15) at midx-write.c:1171
#2 0x000055ee31395f38 in write_midx_file_only (object_dir=0x55ee32570440 ".git/objects",
packs_to_include=0x7ffdde205e20, preferred_pack_name=0x0, refs_snapshot=0x0, flags=15)
at midx-write.c:1274
[...]
In stack frame #0, the code on midx-write.c:590 is using the new pack ID
corresponding to some object which was added from the existing MIDX.
Importantly, the pack from which that object was selected in the
existing MIDX does not appear in the new MIDX as it was excluded via
`--stdin-packs`.
In this instance, the pack in question had pack ID "1" in the existing
MIDX, but since it was excluded from the new MIDX, we never filled in
that entry in the pack_perm table, resulting in:
(gdb) p *ctx->pack_perm@2
$1 = {0, 1515870810}
Which is what causes the segfault above when we try and read:
struct pack_info *pack = &ctx->info[ctx->pack_perm[i]];
if (pack->bitmap_pos == BITMAP_POS_UNKNOWN)
pack->bitmap_pos = 0;
Fundamentally, we should be able to read information from an existing
MIDX when generating a new one. But in practice the midx-write.c code
assumes that we won't run into issues like the above with incongruent
pack IDs, and often makes those assumptions in extremely subtle and
fragile ways.
Instead, let's avoid reading from an existing MIDX altogether, and stick
with the pre-d6a8c58675 implementation. Harden against any regressions
in this area by adding a test which demonstrates these issues.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Memory leaks in "git mv" has been plugged.
* jk/leakfixes:
mv: replace src_dir with a strvec
mv: factor out empty src_dir removal
mv: move src_dir cleanup to end of cmd_mv()
t-strvec: mark variable-arg helper with LAST_ARG_MUST_BE_NULL
t-strvec: use va_end() to match va_start()
The alias-expanded command lines are logged to the trace output.
* iw/trace-argv-on-alias:
run-command: show prepared command
Documentation: alias: add notes on shell expansion
Documentation: alias: rework notes into points
