Clean-up code that handles combinations of incompatible options.
* rs/i18n-cannot-be-used-together:
i18n: factorize even more 'incompatible options' messages
Stale URLs have been updated to their current counterparts (or
archive.org) and HTTP links are replaced with working HTTPS links.
* js/update-urls-in-doc-and-comment:
doc: refer to internet archive
doc: update links for andre-simon.de
doc: switch links to https
doc: update links to current pages
Earlier we stopped relying on commit-graph that (still) records
information about commits that are lost from the object store,
which has negative performance implications. The default has been
flipped to disable this pessimization.
* ps/commit-graph-less-paranoid:
commit-graph: disable GIT_COMMIT_GRAPH_PARANOIA by default
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
Simplify API implementation to delete references by eliminating
duplication.
* ps/ref-deletion-updates:
refs: remove `delete_refs` callback from backends
refs: deduplicate code to delete references
refs/files: use transactions to delete references
t5510: ensure that the packed-refs file needs locking
When calling "packet_read_with_status()" to parse pkt-line encoded
packets, we can turn on the flag "PACKET_READ_CHOMP_NEWLINE" to chomp
newline character for each packet for better line matching. But when
receiving data and progress information using sideband, we should turn
off the flag "PACKET_READ_CHOMP_NEWLINE" to prevent mangling newline
characters from data and progress information.
When both the server and the client support "sideband-all" capability,
we have a dilemma that newline characters in negotiation packets should
be removed, but the newline characters in the progress information
should be left intact.
Add new flag "PACKET_READ_USE_SIDEBAND" for "packet_read_with_status()"
to prevent mangling newline characters in sideband messages.
Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we turn on the "use_sideband" field of the packet_reader,
"packet_reader_read()" will call the function "demultiplex_sideband()"
to parse and consume sideband messages. Sideband fragment which does not
end with "\r" or "\n" will be saved in the sixth parameter "scratch"
and it can be reused and be concatenated when parsing another sideband
message.
In "packet_reader_read()" function, the local variable "scratch" can
only be reused by subsequent sideband messages. But if there is a
payload message between two sideband fragments, the first fragment
which is saved in the local variable "scratch" will be lost.
To solve this problem, we can add a new field "scratch" in
packet_reader to memorize the sideband fragment across different calls
of "packet_reader_read()".
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We can use the test helper program "test-tool pkt-line" to test pkt-line
related functions. E.g.:
* Use "test-tool pkt-line send-split-sideband" to generate sideband
messages.
* Pipe these generated sideband messages to command "test-tool pkt-line
unpack-sideband" to test packet_reader_read() function.
In order to make a complete test of the packet_reader_read() function,
add option parser for command "test-tool pkt-line unpack-sideband".
* To remove newlines in sideband messages, we can use:
$ test-tool pkt-line unpack-sideband --chomp-newline
* To preserve newlines in sideband messages, we can use:
$ test-tool pkt-line unpack-sideband --no-chomp-newline
* To parse sideband messages using "demultiplex_sideband()" inside the
function "packet_reader_read()", we can use:
$ test-tool pkt-line unpack-sideband --reader-use-sideband
We also add new example sideband packets in send_split_sideband() and
add several new test cases in t0070. Among these test cases, we pipe
output of the "send-split-sideband" subcommand to the "unpack-sideband"
subcommand. We found two issues:
1. The two splitted sideband messages "Hello," and " world!\n" should
be concatenated together. But when we turn on use_sideband field of
reader to parse sideband messages, the first part of the splitted
message ("Hello,") is lost.
2. The newline characters in sideband 2 (progress info) and sideband 3
(error message) should be preserved, but they are both trimmed.
Will fix the above two issues in subsequent commits.
Signed-off-by: Jiang Xin <zhiyou.jx@alibaba-inc.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There is no 'ref/notes/' hierarchy. '[format] notes = foo' uses notes
that are found in 'refs/notes/foo'.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the recent commit 2e87fca189 (test framework: further deprecate
test_i18ngrep, 2023-10-31), the test_i18ngrep function was
deprecated, and all the callers were updated to call the test_grep
function instead. But test_grep inherited an error message that
still refers to test_i18ngrep by mistake. Correct it so that a
broken call to the test_grep will identify itself as such.
Signed-off-by: Shreyansh Paliwal <shreyanshpaliwalcmsmn@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Use the data type bool and its values true and false to document the
binary return value of skip_prefix() and friends more explicitly.
This first use of stdbool.h, introduced with C99, is meant to check
whether there are platforms that claim support for C99, as tested by
7bc341e21b (git-compat-util: add a test balloon for C99 support,
2021-12-01), but still lack that header for some reason.
A fallback based on a wider type, e.g. int, would have to deal with
comparisons somehow to emulate that any non-zero value is true:
bool b1 = 1;
bool b2 = 2;
if (b1 == b2) puts("This is true.");
int i1 = 1;
int i2 = 2;
if (i1 == i2) puts("Not printed.");
#define BOOLEQ(a, b) (!(a) == !(b))
if (BOOLEQ(i1, i2)) puts("This is true.");
So we'd be better off using bool everywhere without a fallback, if
possible. That's why this patch doesn't include any.
Signed-off-by: René Scharfe <l.s.r@web.de>
Acked-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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>
The test case "fetch porcelain output" checks output of the fetch
command. The error output must be empty with the follow assertion:
test_must_be_empty stderr
But this assertion fails if using atomic fetch. Refactor this test case
to use different fetch options by splitting it into three test cases.
1. "setup for fetch porcelain output".
2. "fetch porcelain output": for non-atomic fetch.
3. "fetch porcelain output (atomic)": for atomic fetch.
Add new command "test_commit ..." in the first test case, so that if we
run these test cases individually (--run=4-6), "git rev-parse HEAD~"
command will work properly. Run the above test cases, we can find that
one test case has a known breakage, as shown below:
ok 4 - setup for fetch porcelain output
ok 5 - fetch porcelain output # TODO known breakage vanished
not ok 6 - fetch porcelain output (atomic) # TODO known breakage
The failed test case has an error message with only the error prompt but
no message body, as follows:
'stderr' is not empty, it contains:
error:
In a later commit, we will fix this issue.
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>
A handful of manual pages called MERGE_AUTOSTASH a "special ref",
but there is nothing special about it. It merely is yet another
pseudoref.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A handful of manual pages called AUTO_MERGE a "special ref", but
there is nothing special about it. It merely is yet another
pseudoref.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The description of "git bisect --no-checkout" called BISECT_HEAD a
"special ref", but there is nothing special about it. It merely is
yet another pseudoref.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The introductory text in "git help git" that describes HEAD called
it "a special ref". It is special compared to the more regular refs
like refs/heads/master and refs/tags/v1.0.0, but not that special,
unlike truly special ones like FETCH_HEAD.
Rewrite a few sentences to also introduce the distinction between a
regular ref that contain the object name and a symbolic ref that
contain the name of another ref. Update the description of HEAD
that point at the current branch to use the more correct term, a
"symbolic ref".
This was found as part of auditing the documentation and in-code
comments for uses of "special ref" that refer merely a "pseudo ref".
Signed-off-by: Junio C Hamano <gitster@pobox.com>
With one exception, the synopsis for `git add` consistently lists the
short counterpart alongside the long-form of each option (for instance,
"[--edit | -e]"). The exception is that -A is not mentioned alongside
--all. Fix this inconsistency
Reported-by: Benjamin Lehmann <ben.lehmann@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "check-chainlint" target runs automatically when running tests and
performs self-checks to verify that the chainlinter itself produces the
expected output. Originally, the chainlinter was implemented via sed,
but the infrastructure has been rewritten in fb41727b7e (t: retire
unused chainlint.sed, 2022-09-01) to use a Perl script instead.
The rewrite caused some slight whitespace changes in the output that are
ultimately not of much importance. In order to be able to assert that
the actual chainlinter errors match our expectations we thus have to
ignore whitespace characters when diffing them. As the `-w` flag is not
in POSIX we try to use `git diff -w --no-index` before we fall back to
`diff -w -u`.
To accomodate for cases where the host system has no Git installation we
use the locally-compiled version of Git. This can result in problems
though when the Git project's repository is using extensions that the
locally-compiled version of Git doesn't understand. It will refuse to
run and thus cause the checks to fail.
Instead of improving the detection logic, fix our ".expect" files so
that we do not need any post-processing at all anymore. This allows us
to drop the `-w` flag when diffing so that we can always use diff(1)
now.
Note that we keep some of the post-processing of `chainlint.pl` output
intact to strip leading line numbers generated by the script. Having
these would cause a rippling effect whenever we add a new test that
sorts into the middle of existing tests and would require us to
renumerate all subsequent lines, which seems rather pointless.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
To ensure that we don't regress either the size or runtime performance
of multi-pack reuse, add a performance test to measure both of these.
The test partitions the objects in GIT_TEST_PERF_LARGE_REPO into 1, 10,
and 100 packs, and then tries to perform a "clone" at each stage with
both single- and multi-pack reuse enabled.
Note that the `repack_into_n_chunks()` function in this new test script
differs from the existing `repack_into_n()`. The former partitions the
repository into N equal-sized chunks, while the latter produces N packs
of five commits each (plus their objects), and then another pack with
the remainder.
On git.git, I can produce the following results on my machine:
Test this tree
--------------------------------------------------------------------------------
5332.3: clone for 1-pack scenario (single-pack reuse) 1.57(2.99+0.15)
5332.4: clone size for 1-pack scenario (single-pack reuse) 231.8M
5332.5: clone for 1-pack scenario (multi-pack reuse) 1.79(2.96+0.21)
5332.6: clone size for 1-pack scenario (multi-pack reuse) 231.7M
5332.9: clone for 10-pack scenario (single-pack reuse) 3.89(16.75+0.35)
5332.10: clone size for 10-pack scenario (single-pack reuse) 209.9M
5332.11: clone for 10-pack scenario (multi-pack reuse) 1.56(2.99+0.17)
5332.12: clone size for 10-pack scenario (multi-pack reuse) 224.4M
5332.15: clone for 100-pack scenario (single-pack reuse) 8.24(54.31+0.59)
5332.16: clone size for 100-pack scenario (single-pack reuse) 278.3M
5332.17: clone for 100-pack scenario (multi-pack reuse) 2.13(2.44+0.33)
5332.18: clone size for 100-pack scenario (multi-pack reuse) 357.9M
Signed-off-by: Taylor Blau <me@ttaylorr.com>
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>
Introduce a helper function which looks for a specific (category, key,
value) tuple in the output of a trace2 event stream.
We will use this function in a future patch to ensure that the expected
number of objects are reused from an expected number of packs.
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>
Now that the pack-objects code is equipped to handle reusing objects
from multiple packs, prepare the pack-bitmap code to mark objects from
multiple packs as reuse candidates.
In order to prepare the pack-bitmap code for this change, remove the
same set of assumptions we unwound in previous commits from the helper
function `reuse_partial_packfile_from_bitmap_1()`, in preparation for it
to be called in a loop over the set of bitmapped packs in a following
commit.
Most importantly, we can no longer assume that the bit position
corresponding to the first object in a given reuse pack candidate is at
the beginning of the bitmap itself.
For the single pack that this assumption is still true for (in MIDX
bitmaps, this is the preferred pack, in single-pack bitmaps it is the
pack the bitmap is tied to), we can still use our whole-words
optimization.
But for all subsequent packs, we can not make use of this optimization,
since it assumes that all delta bases are being sent from the same pack,
which would break if we are sending OFS_DELTAs down to the client. To
understand why, consider two packs, P1 and P2 where:
- P1 has object A which is a delta on base B
- P2 has its own copy of B, in addition to other objects
Suppose that the MIDX which covers P1 and P2 selected its copy of A from
P1, but selected its copy of B from P2. Since A is a delta of B, but the
base was selected from a different pack, sending the bytes corresponding
to A as an OFS_DELTA verbatim from P1 would be incorrect, since we don't
guarantee that B is in the same place relative to A in the generated
pack as in P1.
For now, we detect and reject these cross-pack deltas by searching for
the (pack_id, offset) pair for the delta's base object (using the same
pack_id as the pack containing the delta'd object) in the MIDX. If we
find a match, that means that the MIDX did indeed pick the base object
from the same pack, and we are OK to reuse the delta.
If we don't find a match, however, that means that the base object was
selected from a different pack in the MIDX, and we can let the slower
path handle re-delta'ing our candidate object.
In the future, there are a couple of other things we could do, namely:
- Turn any cross-pack deltas (which are stored as OFS_DELTAs) into
REF_DELTAs. We already do this today when reusing an OFS_DELTA
without `--delta-base-offset` enabled, so it's not a huge stretch to
do the same for cross-pack deltas even when `--delta-base-offset` is
enabled.
This would work, but would obviously result in larger-than-necessary
packs, as we in theory *could* represent these cross-pack deltas by
patching an existing OFS_DELTA. But it's not clear how much that
would matter in practice. I suspect it would have a lot to do with
how you pack your repository in the first place.
- Finally, we could patch OFS_DELTAs across packs in a similar fashion
as we do today for OFS_DELTAs within a single pack on either side of
a gap. This would result in the smallest packs of the three options
here, but implementing this would be more involved.
At minimum, you'd have to keep the reusable chunks list for all
reused packs, not just the one we're currently processing. And you'd
have to ensure that any bases which are a part of cross-pack deltas
appear before the delta. I think this is possible to do, but would
require assembling the reusable chunks list potentially in a
different order than they appear in the source packs.
For now, let's pursue the simplest approach and reject any cross-pack
deltas.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Now that we have extracted the `midx_key_to_pack_pos()` function, we can
implement the `midx_pair_to_pack_pos()` function which accepts (pack_id,
offset) tuples and returns an index into the psuedo-pack order.
This will be used in a following commit in order to figure out whether
or not the MIDX chose a given delta's base object from the same pack as
the delta resides in. It will do so by locating the base object's offset
in the pack, and then performing a binary search using the same pack ID
with the base object's offset.
If (and only if) it finds a match (at any position) we can guarantee
that the MIDX selected both halves of the delta/base pair from the same
pack.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `midx_to_pack_pos()` function implements a binary search over
objects in the MIDX between lexical and pseudo-pack order. It does this
by taking in an index into the lexical order (i.e. the same argument
you'd use for `nth_midxed_object_id()` and similar) and spits out a
position in the pseudo-pack order.
This works for all callers, since they currently all are translating
from lexical order to pseudo-pack order. But future callers may want to
translate a known (offset, pack_id) tuple into an index into the
psuedo-pack order, without knowing where that (offset, pack_id) tuple
appears in lexical order.
Prepare for implementing a function that translates between a (offset,
pack_id) tuple into an index into the psuedo-pack order by extracting a
helper function which does just that, and then reimplementing
midx_to_pack_pos() in terms of it.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When performing a binary search over the objects in a MIDX's bitmap
(i.e. in pseudo-pack order), the reader reconstructs the pseudo-pack
ordering using a combination of (a) the preferred pack, (b) the pack's
lexical position in the MIDX based on pack names, and (c) the object
offset within the pack.
In order to perform this binary search, the reader must know the
identity of the preferred pack. This could be stored in the MIDX, but
isn't for historical reasons, mostly because it can easily be inferred
at read-time by looking at the object in the first bit position and
finding out which pack it was selected from in the MIDX, like so:
nth_midxed_pack_int_id(m, pack_pos_to_midx(m, 0));
In midx_to_pack_pos() which performs this binary search, we look up the
identity of the preferred pack before each search. This is relatively
quick, since it involves two table-driven lookups (one in the MIDX's
revindex for `pack_pos_to_midx()`, and another in the MIDX's object
table for `nth_midxed_pack_int_id()`).
But since the preferred pack does not change after the MIDX is written,
it is safe to cache this value on the MIDX itself.
Write a helper to do just that, and rewrite all of the existing
call-sites that care about the identity of the preferred pack in terms
of this new helper.
This will prepare us for a subsequent patch where we will need to binary
search through the MIDX's pseudo-pack order multiple times.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In a similar fashion as other checked cast functions in this header
(such as `cast_size_t_to_ulong()` and `cast_size_t_to_int()`), implement
a checked cast function for going from a size_t to a uint32_t value.
This function will be utilized in a future commit which needs to make
such a conversion.
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>
The routines pack-objects uses to perform verbatim pack-reuse are:
- write_reused_pack_one()
- write_reused_pack_verbatim()
- write_reused_pack()
, all of which assume that there is exactly one packfile being reused:
the global constant `reuse_packfile`.
Prepare for reusing objects from multiple packs by making reuse packfile
a parameter of each of the above functions in preparation for calling
these functions in a loop with multiple packfiles.
Note that we still have the global "reuse_packfile", but pass it through
each of the above function's parameter lists, eliminating all but one
direct access (the top-level caller in `write_pack_file()`). Even after
this series, we will still have a global, but it will hold the array of
reusable packfiles, and we'll pass them one at a time to these functions
in a loop.
Note also that we will eventually need to pass a `bitmapped_pack`
instead of a `packed_git` in order to hold onto additional information
required for reuse (such as the bit position of the first object
belonging to that pack). But that change will be made in a future commit
so as to minimize the noise below as much as possible.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Further prepare for enabling verbatim pack-reuse over multiple packfiles
by changing the signature of reuse_partial_packfile_from_bitmap() to
populate an array of `struct bitmapped_pack *`'s instead of a pointer to
a single packfile.
Since the array we're filling out is sized dynamically[^1], add an
additional `size_t *` parameter which will hold the number of reusable
packs (equal to the number of elements in the array).
Note that since we still have not implemented true multi-pack reuse,
these changes aren't propagated out to the rest of the caller in
builtin/pack-objects.c.
In the interim state, we expect that the array has a single element, and
we use that element to fill out the static `reuse_packfile` variable
(which is a bog-standard `struct packed_git *`). Future commits will
continue to push this change further out through the pack-objects code.
[^1]: That is, even though we know the number of packs which are
candidates for pack-reuse, we do not know how many of those
candidates we can actually reuse.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The signature of `reuse_partial_packfile_from_bitmap()` currently takes
in a bitmap, as well as three output parameters (filled through
pointers, and passed as arguments), and also returns an integer result.
The output parameters are filled out with: (a) the packfile used for
pack-reuse, (b) the number of objects from that pack that we can reuse,
and (c) a bitmap indicating which objects we can reuse. The return value
is either -1 (when there are no objects to reuse), or 0 (when there is
at least one object to reuse).
Some of these parameters are redundant. Notably, we can infer from the
bitmap how many objects are reused by calling bitmap_popcount(). And we
can similar compute the return value based on that number as well.
As such, clean up the signature of this function to drop the "*entries"
parameter, as well as the int return value, since the single caller of
this function can infer these values themself.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In a future commit, we will want to check whether or not a bitmap has
any bits set in any of its words. The best way to do this (prior to the
existence of this patch) is to call `bitmap_popcount()` and check
whether the result is non-zero.
But this is semi-wasteful, since we do not need to know the exact number
of bits set, only whether or not there is at least one of them.
Implement a new helper function to check just that.
Suggested-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When trying to assemble a pack with bitmaps using `--use-bitmap-index`,
`pack-objects` asks the pack-bitmap machinery for a bitmap which
indicates the set of objects we can "reuse" verbatim from on-disk.
This set is roughly comprised of: a prefix of objects in the bitmapped
pack (or preferred pack, in the case of a multi-pack reachability
bitmap), plus any other objects not included in the prefix, excluding
any deltas whose base we are not sending in the resulting pack.
The pack-bitmap machinery is responsible for computing this bitmap, and
does so with the following functions:
- reuse_partial_packfile_from_bitmap()
- try_partial_reuse()
In the existing implementation, the first function is responsible for
(a) marking the prefix of objects in the reusable pack, and then (b)
calling try_partial_reuse() on any remaining objects to ensure that they
are also reusable (and removing them from the bitmapped set if they are
not).
Likewise, the `try_partial_reuse()` function is responsible for checking
whether an isolated object (that is, an object from the bitmapped
pack/preferred pack not contained in the prefix from earlier) may be
reused, i.e. that it isn't a delta of an object that we are not sending
in the resulting pack.
These functions are based on two core assumptions, which we will unwind
in this and the following commits:
1. There is only a single pack from the bitmap which is eligible for
verbatim pack-reuse. For single-pack bitmaps, this is trivially the
bitmapped pack. For multi-pack bitmaps, this is (currently) the
MIDX's preferred pack.
2. The pack eligible for reuse has its first object in bit position 0,
and all objects from that pack follow in pack-order from that first
bit position.
In order to perform verbatim pack reuse over multiple packs, we must
unwind these two assumptions. Most notably, in order to reuse bits from
a given packfile, we need to know the first bit position occupied by
an object form that packfile. To propagate this information around, pass
a `struct bitmapped_pack *` anywhere we previously passed a `struct
packed_git *`, since the former contains the bitmap position we're
interested in (as well as a pointer to the latter).
As an additional step, factor out a sub-routine from the main
`reuse_partial_packfile_from_bitmap()` function, called
`reuse_partial_packfile_from_bitmap_1()`. This new function will be
responsible for figuring out which objects may be reused from a single
pack, and the existing function will dispatch multiple calls to its new
helper function for each reusable pack.
Consequently, `reuse_partial_packfile_from_bitmap()` will now maintain
an array of reusable packs instead of a single such pack. We currently
expect that array to have only a single element, so this awkward state
is short-lived. It will serve as useful scaffolding in subsequent
commits as we begin to work towards enabling multi-pack reuse.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The multi-pack index API exposes a `midx_contains_pack()` function that
takes in a string ending in either ".idx" or ".pack" and returns whether
or not the MIDX contains a given pack corresponding to that string.
There is no corresponding function to locate the position of a pack
within the MIDX's pack order (sorted lexically by pack filename).
We could add an optional out parameter to `midx_contains_pack()` that is
filled out with the pack's position when the parameter is non-NULL. To
minimize the amount of fallout from this change, instead introduce a new
function by renaming `midx_contains_pack()` to `midx_locate_pack()`,
adding that output parameter, and then reimplementing
`midx_contains_pack()` in terms of it.
Future patches will make use of this new function.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When a multi-pack bitmap is used to implement verbatim pack reuse (that
is, when verbatim chunks from an on-disk packfile are copied
directly[^1]), it does so by using its "preferred pack" as the source
for pack-reuse.
This allows repositories to pack the majority of their objects into a
single (often large) pack, and then use it as the single source for
verbatim pack reuse. This increases the amount of objects that are
reused verbatim (and consequently, decrease the amount of time it takes
to generate many packs). But this performance comes at a cost, which is
that the preferred packfile must pace its growth with that of the entire
repository in order to maintain the utility of verbatim pack reuse.
As repositories grow beyond what we can reasonably store in a single
packfile, the utility of verbatim pack reuse diminishes. Or, at the very
least, it becomes increasingly more expensive to maintain as the pack
grows larger and larger.
It would be beneficial to be able to perform this same optimization over
multiple packs, provided some modest constraints (most importantly, that
the set of packs eligible for verbatim reuse are disjoint with respect
to the subset of their objects being sent).
If we assume that the packs which we treat as candidates for verbatim
reuse are disjoint with respect to any of their objects we may output,
we need to make only modest modifications to the verbatim pack-reuse
code itself. Most notably, we need to remove the assumption that the
bits in the reachability bitmap corresponding to objects from the single
reuse pack begin at the first bit position.
Future patches will unwind these assumptions and reimplement their
existing functionality as special cases of the more general assumptions
(e.g. that reuse bits can start anywhere within the bitset, but happen
to start at 0 for all existing cases).
This patch does not yet relax any of those assumptions. Instead, it
implements a foundational data-structure, the "Bitampped Packs" (`BTMP`)
chunk of the multi-pack index. The `BTMP` chunk's contents are described
in detail here. Importantly, the `BTMP` chunk contains information to
map regions of a multi-pack index's reachability bitmap to the packs
whose objects they represent.
For now, this chunk is only written, not read (outside of the test-tool
used in this patch to test the new chunk's behavior). Future patches
will begin to make use of this new chunk.
[^1]: Modulo patching any `OFS_DELTA`'s that cross over a region of the
pack that wasn't used verbatim.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When selecting which packfiles will be written while generating a MIDX,
the MIDX internals fill out a 'struct pack_info' with various pieces of
book-keeping.
Instead of filling out each field of the `pack_info` structure
individually in each of the two spots that modify the array of such
structures (`ctx->info`), extract a common routine that does this for
us.
This reduces the code duplication by a modest amount. But more
importantly, it zero-initializes the structure before assigning values
into it. This hardens us for a future change which will add additional
fields to this structure which (until this patch) was not
zero-initialized.
As a result, any new fields added to the `pack_info` structure need only
be updated in a single location, instead of at each spot within midx.c.
There are no functional changes in this patch.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `find_objects()` function creates an object_list for any tips of the
reachability query which do not have corresponding bitmaps.
The object_list is not used outside of `find_objects()`, but we never
free it with `object_list_free()`, resulting in a leak. Let's plug that
leak by calling `object_list_free()`, which results in t6113 becoming
leak-free.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The `bb_commit` commit slab is used by the pack-bitmap-write machinery
to track various pieces of bookkeeping used to generate reachability
bitmaps.
Even though we clear the slab when freeing the bitmap_builder struct
(with `bitmap_builder_clear()`), there are still pointers which point to
locations in memory that have not yet been freed, resulting in a leak.
Plug the leak by introducing a suitable `free_fn` for the `struct
bb_commit` type, and make sure it is called on each member of the slab
via the `deep_clear_bb_data()` function.
Note that it is possible for both of the arguments to `bitmap_free()` to
be NULL, but `bitmap_free()` is a noop for NULL arguments, so it is OK
to pass them unconditionally.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The pack-objects internals use a packing_data struct to track what
objects are part of the pack(s) being formed.
Since these structures contain allocated fields, failing to
appropriately free() them results in a leak. Plug that leak by
introducing a clear_packing_data() function, and call it in the
appropriate spots.
This is a fairly straightforward leak to plug, since none of the callers
expect to read any values or have any references to parts of the address
space being freed.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our unquote_comment() function is recursive; when it sees a comment
within a comment, like:
(this is an (embedded) comment)
it recurses to handle the inner comment. This is fine for practical use,
but it does mean that you can easily run out of stack space with a
malicious header. For example:
perl -e 'print "From: ", "(" x 2**18;' |
git mailinfo /dev/null /dev/null
segfaults on my system. And since mailinfo is likely to be fed untrusted
input from the Internet (if not by human users, who might recognize a
garbage header, but certainly there are automated systems that apply
patches from a list) it may be possible for an attacker to trigger the
problem.
That said, I don't think there's an interesting security vulnerability
here. All an attacker can do is make it impossible to parse their email
and apply their patch, and there are lots of ways to generate bogus
emails. So it's more of an annoyance than anything.
But it's pretty easy to fix it. The recursion is not helping us preserve
any particular state from each level. The only flag in our parsing is
take_next_literally, and we can never recurse when it is set (since the
start of a new comment implies it was not backslash-escaped). So it is
really only useful for finding the end of the matched pair of
parentheses. We can do that easily with a simple depth counter.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
