Introduce a new extension "refstorage" so that we can mark a
repository that uses a non-default ref backend, like reftable.
* ps/refstorage-extension:
t9500: write "extensions.refstorage" into config
builtin/clone: introduce `--ref-format=` value flag
builtin/init: introduce `--ref-format=` value flag
builtin/rev-parse: introduce `--show-ref-format` flag
t: introduce GIT_TEST_DEFAULT_REF_FORMAT envvar
setup: introduce GIT_DEFAULT_REF_FORMAT envvar
setup: introduce "extensions.refStorage" extension
setup: set repository's formats on init
setup: start tracking ref storage format
refs: refactor logic to look up storage backends
worktree: skip reading HEAD when repairing worktrees
t: introduce DEFAULT_REPO_FORMAT prereq
Streaming spans of packfile data used to be done only from a
single, primary, pack in a repository with multiple packfiles. It
has been extended to allow reuse from other packfiles, too.
* tb/multi-pack-verbatim-reuse: (26 commits)
t/perf: add performance tests for multi-pack reuse
pack-bitmap: enable reuse from all bitmapped packs
pack-objects: allow setting `pack.allowPackReuse` to "single"
t/test-lib-functions.sh: implement `test_trace2_data` helper
pack-objects: add tracing for various packfile metrics
pack-bitmap: prepare to mark objects from multiple packs for reuse
pack-revindex: implement `midx_pair_to_pack_pos()`
pack-revindex: factor out `midx_key_to_pack_pos()` helper
midx: implement `midx_preferred_pack()`
git-compat-util.h: implement checked size_t to uint32_t conversion
pack-objects: include number of packs reused in output
pack-objects: prepare `write_reused_pack_verbatim()` for multi-pack reuse
pack-objects: prepare `write_reused_pack()` for multi-pack reuse
pack-objects: pass `bitmapped_pack`'s to pack-reuse functions
pack-objects: keep track of `pack_start` for each reuse pack
pack-objects: parameterize pack-reuse routines over a single pack
pack-bitmap: return multiple packs via `reuse_partial_packfile_from_bitmap()`
pack-bitmap: simplify `reuse_partial_packfile_from_bitmap()` signature
ewah: implement `bitmap_is_empty()`
pack-bitmap: pass `bitmapped_pack` struct to pack-reuse functions
...
"git sparse-checkout (add|set) --[no-]cone --end-of-options" did
not handle "--end-of-options" correctly after a recent update.
* en/sparse-checkout-eoo:
sparse-checkout: be consistent with end of options markers
"git sparse-checkout set" added default patterns even when the
patterns are being fed from the standard input, which has been
corrected.
* jc/sparse-checkout-set-default-fix:
sparse-checkout: use default patterns for 'set' only !stdin
Remove unused header "#include".
* en/header-cleanup:
treewide: remove unnecessary includes in source files
treewide: add direct includes currently only pulled in transitively
trace2/tr2_tls.h: remove unnecessary include
submodule-config.h: remove unnecessary include
pkt-line.h: remove unnecessary include
line-log.h: remove unnecessary include
http.h: remove unnecessary include
fsmonitor--daemon.h: remove unnecessary includes
blame.h: remove unnecessary includes
archive.h: remove unnecessary include
treewide: remove unnecessary includes in source files
treewide: remove unnecessary includes from header files
The t5309 script triggers a racy false positive with SANITIZE=leak on a
multi-core system. Running with "--stress --run=6" usually fails within
10 seconds or so for me, complaining with something like:
+ git index-pack --fix-thin --stdin
fatal: REF_DELTA at offset 46 already resolved (duplicate base 01d7713666f4de822776c7622c10f1b07de280dc?)
=================================================================
==3904583==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 32 byte(s) in 1 object(s) allocated from:
#0 0x7fa790d01986 in __interceptor_realloc ../../../../src/libsanitizer/lsan/lsan_interceptors.cpp:98
#1 0x7fa790add769 in __pthread_getattr_np nptl/pthread_getattr_np.c:180
#2 0x7fa790d117c5 in __sanitizer::GetThreadStackTopAndBottom(bool, unsigned long*, unsigned long*) ../../../../src/libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp:150
#3 0x7fa790d11957 in __sanitizer::GetThreadStackAndTls(bool, unsigned long*, unsigned long*, unsigned long*, unsigned long*) ../../../../src/libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp:598
#4 0x7fa790d03fe8 in __lsan::ThreadStart(unsigned int, unsigned long long, __sanitizer::ThreadType) ../../../../src/libsanitizer/lsan/lsan_posix.cpp:51
#5 0x7fa790d013fd in __lsan_thread_start_func ../../../../src/libsanitizer/lsan/lsan_interceptors.cpp:440
#6 0x7fa790adc3eb in start_thread nptl/pthread_create.c:444
#7 0x7fa790b5ca5b in clone3 ../sysdeps/unix/sysv/linux/x86_64/clone3.S:81
SUMMARY: LeakSanitizer: 32 byte(s) leaked in 1 allocation(s).
Aborted
What happens is this:
0. We construct a bogus pack with a duplicate object in it and trigger
index-pack.
1. We spawn a bunch of worker threads to resolve deltas (on my system
it is 16 threads).
2. One of the threads sees the duplicate object and bails by calling
exit(), taking down all of the threads. This is expected and is the
point of the test.
3. At the time exit() is called, we may still be spawning threads from
the main process via pthread_create(). LSan hooks thread creation
to update its book-keeping; it has to know where each thread's
stack is (so it can find entry points for reachable memory). So it
calls pthread_getattr_np() to get information about the new thread.
That may allocate memory that must be freed with a matching call to
pthread_attr_destroy(). Probably LSan does that immediately, but
if you're unlucky enough, the exit() will happen while it's between
those two calls, and the allocated pthread_attr_t appears as a
leak.
This isn't a real leak. It's not even in our code, but rather in the
LSan instrumentation code. So we could just ignore it. But the false
positive can cause people to waste time tracking it down.
It's possibly something that LSan could protect against (e.g., cover the
getattr/destroy pair with a mutex, and then in the final post-exit()
check for leaks try to take the same mutex). But I don't know enough
about LSan to say if that's a reasonable approach or not (or if my
analysis is even completely correct).
In the meantime, it's pretty easy to avoid the race by making creation
of the worker threads "atomic". That is, we'll spawn all of them before
letting any of them start to work. That's easy to do because we already
have a work_lock() mutex for handing out that work. If the main process
takes it, then all of the threads will immediately block until we've
finished spawning and released it.
This shouldn't make any practical difference for non-LSan runs. The
thread spawning is quick, and could happen before any worker thread gets
scheduled anyway.
Probably other spots that use threads are subject to the same issues.
But since we have to manually insert locking (and since this really is
kind of a hack), let's not bother with them unless somebody experiences
a similar racy false-positive in practice.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Assorted changes around pseudoref handling.
* ps/pseudo-refs:
bisect: consistently write BISECT_EXPECTED_REV via the refdb
refs: complete list of special refs
refs: propagate errno when reading special refs fails
wt-status: read HEAD and ORIG_HEAD via the refdb
Doc updates to clarify what an "unborn branch" means.
* jc/orphan-unborn:
orphan/unborn: fix use of 'orphan' in end-user facing messages
orphan/unborn: add to the glossary and use them consistently
Code clean-up.
* la/trailer-cleanups:
trailer: use offsets for trailer_start/trailer_end
trailer: find the end of the log message
commit: ignore_non_trailer computes number of bytes to ignore
Introduce a new `--ref-format` value flag for git-clone(1) that allows
the user to specify the ref format that is to be used for a newly
initialized repository.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce a new `--ref-format` value flag for git-init(1) that allows
the user to specify the ref format that is to be used for a newly
initialized repository.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce a new `--show-ref-format` to git-rev-parse(1) that causes it
to print the ref format used by a repository.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Introduce a new "extensions.refStorage" extension that allows us to
specify the ref storage format used by a repository. For now, the only
supported format is the "files" format, but this list will likely soon
be extended to also support the upcoming "reftable" format.
There have been discussions on the Git mailing list in the past around
how exactly this extension should look like. One alternative [1] that
was discussed was whether it would make sense to model the extension in
such a way that backends are arbitrarily stackable. This would allow for
a combined value of e.g. "loose,packed-refs" or "loose,reftable", which
indicates that new refs would be written via "loose" files backend and
compressed into "packed-refs" or "reftable" backends, respectively.
It is arguable though whether this flexibility and the complexity that
it brings with it is really required for now. It is not foreseeable that
there will be a proliferation of backends in the near-term future, and
the current set of existing formats and formats which are on the horizon
can easily be configured with the much simpler proposal where we have a
single value, only.
Furthermore, if we ever see that we indeed want to gain the ability to
arbitrarily stack the ref formats, then we can adapt the current
extension rather easily. Given that Git clients will refuse any unknown
value for the "extensions.refStorage" extension they would also know to
ignore a stacked "loose,packed-refs" in the future.
So let's stick with the easy proposal for the time being and wire up the
extension.
[1]: <pull.1408.git.1667846164.gitgitgadget@gmail.com>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In order to discern which ref storage format a repository is supposed to
use we need to start setting up and/or discovering the format. This
needs to happen in two separate code paths.
- The first path is when we create a repository via `init_db()`. When
we are re-initializing a preexisting repository we need to retain
the previously used ref storage format -- if the user asked for a
different format then this indicates an error and we error out.
Otherwise we either initialize the repository with the format asked
for by the user or the default format, which currently is the
"files" backend.
- The second path is when discovering repositories, where we need to
read the config of that repository. There is not yet any way to
configure something other than the "files" backend, so we can just
blindly set the ref storage format to this backend.
Wire up this logic so that we have the ref storage format always readily
available when needed. As there is only a single backend and because it
is not configurable we cannot yet verify that this tracking works as
expected via tests, but tests will be added in subsequent commits. To
countermand this ommission now though, raise a BUG() in case the ref
storage format is not set up properly in `ref_store_init()`.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git clone" has been prepared to allow cloning a repository with
non-default hash function into a repository that uses the reftable
backend.
* ps/clone-into-reftable-repository:
builtin/clone: create the refdb with the correct object format
builtin/clone: skip reading HEAD when retrieving remote
builtin/clone: set up sparse checkout later
builtin/clone: fix bundle URIs with mismatching object formats
remote-curl: rediscover repository when fetching refs
setup: allow skipping creation of the refdb
setup: extract function to create the refdb
"git fetch --atomic" issued an unnecessary empty error message,
which has been corrected.
* jx/fetch-atomic-error-message-fix:
fetch: no redundant error message for atomic fetch
t5574: test porcelain output of atomic fetch
Code clean-up for sanity checking of command line options for "git
show-ref".
* rs/show-ref-incompatible-options:
show-ref: use die_for_incompatible_opt3()
"git checkout -B <branch> [<start-point>]" allowed a branch that is
in use in another worktree to be updated and checked out, which
might be a bit unexpected. The rule has been tightened, which is a
breaking change. "--ignore-other-worktrees" option is required to
unbreak you, if you are used to the current behaviour that "-B"
overrides the safety.
* jc/checkout-B-branch-in-use:
checkout: forbid "-B <branch>" from touching a branch used elsewhere
checkout: refactor die_if_checked_out() caller
"git sparse-checkout set ---no-cone" uses default patterns when none
is given from the command line, but it should do so ONLY when
--stdin is not being used. Right now, add_patterns_from_input()
called when reading from the standard input is sloppy and does not
check if there are extra command line parameters that the command
will silently ignore, but that will change soon and not setting this
unnecessary and unused default patterns start to matter when it gets
fixed.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
93851746 (parse-options: decouple "--end-of-options" and "--",
2023-12-06) updated the world order to make callers of parse-options
that set PARSE_OPT_KEEP_UNKNOWN_OPT responsible for deciding what to
do with "--end-of-options" they may see after parse_options() returns.
This made a previous bug in sparse-checkout more visible; namely,
that
git sparse-checkout [add|set] --[no-]cone --end-of-options ...
would simply treat "--end-of-options" as one of the paths to include in
the sparse-checkout. But this was already problematic before; namely,
git sparse-checkout [add|set| --[no-]cone --sikp-checks ...
would not give an error on the mis-typed "--skip-checks" but instead
simply treat "--sikp-checks" as a path or pattern to include in the
sparse-checkout, which is highly unfriendly.
This behavior began when the command was converted to parse-options in
7bffca95ea (sparse-checkout: add '--stdin' option to set subcommand,
2019-11-21). Back then it was just called KEEP_UNKNOWN. Later it was
renamed to KEEP_UNKNOWN_OPT in 99d86d60e5 (parse-options:
PARSE_OPT_KEEP_UNKNOWN only applies to --options, 2022-08-19) to clarify
that it was only about dashed options; we always keep non-option
arguments. Looking at that original patch, both Peff and I think that
the author was simply confused about the mis-named option, and really
just wanted to keep the non-option arguments. We never should have used
the flag all along (and the other cases were cargo-culted within the
file).
Remove the erroneous PARSE_OPT_KEEP_UNKNOWN_OPT flag now to fix this
bug. Note that this does mean that anyone who might have been using
git sparse-checkout [add|set] [--[no-]cone] --foo --bar
to request paths or patterns '--foo' and '--bar' will now have to use
git sparse-checkout [add|set] [--[no-]cone] -- --foo --bar
That makes sparse-checkout more consistent with other git commands,
provides users much friendlier error messages and behavior, and is
consistent with the all-caps warning in git-sparse-checkout.txt that
this command "is experimental...its behavior...will likely change". :-)
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The next commit will remove a bunch of unnecessary includes, but to do
so, we need some of the lower level direct includes that files rely on
to be explicitly specified.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The unnecessary include in the header transitively pulled in some
other headers actually needed by source files, though. Have those
source files explicitly include the headers they need.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Each of these were checked with
gcc -E -I. ${SOURCE_FILE} | grep ${HEADER_FILE}
to ensure that removing the direct inclusion of the header actually
resulted in that header no longer being included at all (i.e. that
no other header pulled it in transitively).
...except for a few cases where we verified that although the header
was brought in transitively, nothing from it was directly used in
that source file. These cases were:
* builtin/credential-cache.c
* builtin/pull.c
* builtin/send-pack.c
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Use mem_pool_calloc() to get a zeroed buffer instead of zeroing it
ourselves. This makes the code clearer and less repetitive.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* ps/clone-into-reftable-repository:
builtin/clone: create the refdb with the correct object format
builtin/clone: skip reading HEAD when retrieving remote
builtin/clone: set up sparse checkout later
builtin/clone: fix bundle URIs with mismatching object formats
remote-curl: rediscover repository when fetching refs
setup: allow skipping creation of the refdb
setup: extract function to create the refdb
Code clean-up around use of configuration variables.
* jk/config-cleanup:
sequencer: simplify away extra git_config_string() call
gpg-interface: drop pointless config_error_nonbool() checks
push: drop confusing configset/callback redundancy
config: use git_config_string() for core.checkRoundTripEncoding
diff: give more detailed messages for bogus diff.* config
config: use config_error_nonbool() instead of custom messages
imap-send: don't use git_die_config() inside callback
git_xmerge_config(): prefer error() to die()
config: reject bogus values for core.checkstat
Some codepaths did not correctly parse configuration variables
specified with valueless "true", which has been corrected.
* jk/implicit-true:
fsck: handle NULL value when parsing message config
trailer: handle NULL value when parsing trailer-specific config
submodule: handle NULL value when parsing submodule.*.branch
help: handle NULL value for alias.* config
trace2: handle NULL values in tr2_sysenv config callback
setup: handle NULL value when parsing extensions
config: handle NULL value when parsing non-bools
"git bisect reset" has been taught to clean up state files and refs
even when BISECT_START file is gone.
* jk/bisect-reset-fix:
bisect: always clean on reset
Clean-up code that handles combinations of incompatible options.
* rs/incompatible-options-messages:
worktree: simplify incompatibility message for --orphan and commit-ish
worktree: standardize incompatibility messages
clean: factorize incompatibility message
revision, rev-parse: factorize incompatibility messages about - -exclude-hidden
revision: use die_for_incompatible_opt3() for - -graph/--reverse/--walk-reflogs
repack: use die_for_incompatible_opt3() for -A/-k/--cruft
push: use die_for_incompatible_opt4() for - -delete/--tags/--all/--mirror
In run_am(), a strbuf is used to create a revision argument that is then
added to the argument list for git format-patch using strvec_push().
Use strvec_pushf() to add it directly instead, simplifying the code
and plugging a small leak on the error code path.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When the "--force-with-lease" option was introduced in 28f5d176
(remote.c: add command line option parser for "--force-with-lease",
2013-07-08), the design discussion revolved around the concept of
"compare-and-swap", and it can still be seen in the name used for
variables and helper functions. The end-user facing option name
ended up to be a bit different, so during the development iteration
of the feature, we used this C preprocessor macro to make it easier
to rename it later.
All of that happened more than 10 years ago, and the flexibility
afforded by the CAS_OPT_NAME macro outlived its usefulness. Inline
the constant string for the option name, like all other option names
in the code.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git merge-file" learned to take the "--diff-algorithm" option to
use algorithm different from the default "myers" diff.
* ad/merge-file-diff-algo:
merge-file: add --diff-algorithm option
Clean-up code that handles combinations of incompatible options.
* rs/i18n-cannot-be-used-together:
i18n: factorize even more 'incompatible options' messages
Introduce "git replay", a tool meant on the server side without
working tree to recreate a history.
* cc/git-replay:
replay: stop assuming replayed branches do not diverge
replay: add --contained to rebase contained branches
replay: add --advance or 'cherry-pick' mode
replay: use standard revision ranges
replay: make it a minimal server side command
replay: remove HEAD related sanity check
replay: remove progress and info output
replay: add an important FIXME comment about gpg signing
replay: change rev walking options
replay: introduce pick_regular_commit()
replay: die() instead of failing assert()
replay: start using parse_options API
replay: introduce new builtin
t6429: remove switching aspects of fast-rebase
If an error occurs during an atomic fetch, a redundant error message
will appear at the end of do_fetch(). It was introduced in b3a804663c
(fetch: make `--atomic` flag cover backfilling of tags, 2022-02-17).
Because a failure message is displayed before setting retcode in the
function do_fetch(), calling error() on the err message at the end of
this function may result in redundant or empty error message to be
displayed.
We can remove the redundant error() function, because we know that
the function ref_transaction_abort() never fails. While we can find a
common pattern for calling ref_transaction_abort() by running command
"git grep -A1 ref_transaction_abort", e.g.:
if (ref_transaction_abort(transaction, &error))
error("abort: %s", error.buf);
Following this pattern, we can tolerate the return value of the function
ref_transaction_abort() being changed in the future. We also delay the
output of the err message to the end of do_fetch() to reduce redundant
code. With these changes, the test case "fetch porcelain output
(atomic)" in t5574 will also be fixed.
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now that both the pack-bitmap and pack-objects code are prepared to
handle marking and using objects from multiple bitmapped packs for
verbatim reuse, allow marking objects from all bitmapped packs as
eligible for reuse.
Within the `reuse_partial_packfile_from_bitmap()` function, we no longer
only mark the pack whose first object is at bit position zero for reuse,
and instead mark any pack contained in the MIDX as a reuse candidate.
Provide a handful of test cases in a new script (t5332) exercising
interesting behavior for multi-pack reuse to ensure that we performed
all of the previous steps correctly.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In e704fc7978 (pack-objects: introduce pack.allowPackReuse, 2019-12-18),
the `pack.allowPackReuse` configuration option was introduced, allowing
users to disable the pack reuse mechanism.
To prepare for debugging multi-pack reuse, allow setting configuration
to "single" in addition to the usual bool-or-int values.
"single" implies the same behavior as "true", "1", "yes", and so on. But
it will complement a new "multi" value (to be introduced in a future
commit). When set to "single", we will only perform pack reuse on a
single pack, regardless of whether or not there are multiple MIDX'd
packs.
This requires no code changes (yet), since we only support single pack
reuse.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As part of the multi-pack reuse effort, we will want to add some tests
that assert that we reused a certain number of objects from a certain
number of packs.
We could do this by grepping through the stderr output of
`pack-objects`, but doing so would be brittle in case the output format
changed.
Instead, let's use the trace2 mechanism to log various pieces of
information about the generated packfile, which we can then use to
compare against desired values.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In addition to including the number of objects reused verbatim from a
reuse-pack, include the number of packs from which objects were reused.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function `write_reused_pack_verbatim()` within
`builtin/pack-objects.c` is responsible for writing out a continuous
set of objects beginning at the start of the reuse packfile.
In the existing implementation, we did something like:
while (pos < reuse_packfile_bitmap->word_alloc &&
reuse_packfile_bitmap->words[pos] == (eword_t)~0)
pos++;
if (pos)
/* write first `pos * BITS_IN_WORD` objects from pack */
as an optimization to record a single chunk for the longest continuous
prefix of objects wanted out of the reuse pack, instead of having a
chunk for each individual object. For more details, see bb514de356
(pack-objects: improve partial packfile reuse, 2019-12-18).
In order to retain this optimization in a multi-pack reuse world, we can
no longer assume that the first object in a pack is on a word boundary
in the bitmap storing the set of reusable objects.
Assuming that all objects from the beginning of the reuse packfile up to
the object corresponding to the first bit on a word boundary are part of
the result, consume whole words at a time until the last whole word
belonging to the reuse packfile. Copy those objects to the resulting
packfile, and track that we reused them by recording a single chunk.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function `write_reused_pack()` within `builtin/pack-objects.c` is
responsible for performing pack-reuse on a single pack, and has two main
functions:
- it dispatches a call to `write_reused_pack_verbatim()` to see if we
can reuse portions of the packfile in whole-word chunks
- for any remaining objects (that is, any objects that appear after
the first "gap" in the bitmap), call write_reused_pack_one() on that
object to record it for reuse.
Prepare this function for multi-pack reuse by removing the assumption
that the bit position corresponding to the first object being reused
from a given pack must be at bit position zero.
The changes in this function are mostly straightforward. Initialize `i`
to the position of the first word to contain bits corresponding to that
reuse pack. In most situations, we throw the initialized value away,
since we end up replacing it with the return value from
write_reused_pack_verbatim(), moving us past the section of whole words
that we reused.
Likewise, modify the per-object loop to ignore any bits at the beginning
of the first word that do not belong to the pack currently being reused,
as well as skip to the "done" section once we have processed the last
bit corresponding to this pack.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Further prepare pack-objects to perform verbatim pack-reuse over
multiple packfiles by converting functions that take in a pointer to a
`struct packed_git` to instead take in a pointer to a `struct
bitmapped_pack`.
The additional information found in the bitmapped_pack struct (such as
the bit position corresponding to the beginning of the pack) will be
necessary in order to perform verbatim pack-reuse.
Note that we don't use any of the extra pieces of information contained
in the bitmapped_pack struct, so this step is merely preparatory and
does not introduce any functional changes.
Note further that we do not change the argument type to
write_reused_pack_one(). That function is responsible for copying
sections of the packfile directly and optionally patching any OFS_DELTAs
to account for not reusing sections of the packfile in between a delta
and its base.
As such, that function is (and should remain) oblivious to multi-pack
reuse, and does not require any of the extra pieces of information
stored in the bitmapped_pack struct.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When reusing objects from a pack, we keep track of a set of one or more
`reused_chunk`s, corresponding to sections of one or more object(s) from
a source pack that we are reusing. Each chunk contains two pieces of
information:
- the offset of the first object in the source pack (relative to the
beginning of the source pack)
- the difference between that offset, and the corresponding offset in
the pack we're generating
The purpose of keeping track of these is so that we can patch an
OFS_DELTAs that cross over a section of the reuse pack that we didn't
take.
For instance, consider a hypothetical pack as shown below:
(chunk #2)
__________...
/
/
+--------+---------+-------------------+---------+
... | <base> | <other> | (unused) | <delta> | ...
+--------+---------+-------------------+---------+
\ /
\______________/
(chunk #1)
Suppose that we are sending objects "base", "other", and "delta", and
that the "delta" object is stored as an OFS_DELTA, and that its base is
"base". If we don't send any objects in the "(unused)" range, we can't
copy the delta'd object directly, since its delta offset includes a
range of the pack that we didn't copy, so we have to account for that
difference when patching and reassembling the delta.
In order to compute this value correctly, we need to know not only where
we are in the packfile we're assembling (with `hashfile_total(f)`) but
also the position of the first byte of the packfile that we are
currently reusing. Currently, this works just fine, since when reusing
only a single pack those two values are always identical (because
verbatim reuse is the first thing pack-objects does when enabled after
writing the pack header).
But when reusing multiple packs which have one or more gaps, we'll need
to account for these two values diverging.
Together, these two allow us to compute the reused chunk's offset
difference relative to the start of the reused pack, as desired.
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
