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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Submodule merges are, in general, similar to other merges based on oid
three-way-merge. When a conflict happens, however, Git has two special
cases (introduced in 68d03e4a6e44) on handling the conflict before
yielding it to the user. From the merge-ort and merge-recursive sources:
- "Case #1: a is contained in b or vice versa": both strategies try to
perform a fast-forward in the submodules if the commit referred by the
conflicted submodule is descendant of another;
- "Case #2: There are one or more merges that contain a and b in the
submodule. If there is only one, then present it as a suggestion to the
user, but leave it marked unmerged so the user needs to confirm the
resolution."
Add a small paragraph on merge-strategies.adoc describing this behavior.
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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As we have created an empty .git/branches/ hierarchy until fairly
recently, these directories may be found in modern repositories, but
it is highly unlikely that they are being used.
Reported-by: Jakub Wilk <jwilk@jwilk.net>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Correct the default target in Documentation/Makefile, and
future-proof all Makefiles from similar breakages by declaring the
default target (which happens to be "all") upfront.
* ad/set-default-target-in-makefiles:
Makefile: set default goals in makefiles
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"git merge-tree --stdin" has been improved (including a workaround
for a deadlock).
* pw/merge-tree-stdin-deadlock-fix:
merge-tree: fix link formatting in html docs
merge-tree: improve docs for --stdin
merge-tree: only use basic merge config
merge-tree: remove redundant code
merge-tree --stdin: flush stdout to avoid deadlock
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The documentation of "git commit" and "git rebase" now refer to
commit titles as such, not "subject".
* mh/doc-commit-title-not-subject:
doc: use 'title' consistently
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Two configuration variables about SSL authentication material that
weren't mentioned in the documentations are now mentioned.
* ac/doc-http-ssl-type-config:
docs: indicate http.sslCertType and sslKeyType
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Doc updates.
* en/doc-renormalize:
doc: clarify the intent of the renormalize option in the merge machinery
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Doc updates.
* jc/doc-boolean-synonyms:
doc: centrally document various ways tospell `true` and `false`
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The "git refs migrate" subcommand converts the backend used for ref
storage. It always migrates reflog data as well as refs. Introduce an
option to exclude reflogs from migration, allowing them to be discarded
when they are unnecessary.
This is particularly useful in server-side repositories, where reflogs
are typically not expected. However, some repositories may still have
them due to historical reasons, such as bugs, misconfigurations, or
administrative decisions to enable reflogs for debugging. In such
repositories, it would be optimal to drop reflogs during the migration.
To address this, introduce the '--no-reflog' flag, which prevents reflog
migration. When this flag is used, reflogs from the original reference
backend are migrated. Since only the new reference backend remains in
the repository, all previous reflogs are permanently discarded.
Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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As some issues that can happen with a Git client can be operating system
specific, it can be useful for a server to know which OS a client is
using. In the same way it can be useful for a client to know which OS
a server is using.
Our current agent capability is in the form of "package/version" (e.g.,
"git/1.8.3.1"). Let's extend it to include the operating system name (os)
i.e in the form "package/version-os" (e.g., "git/1.8.3.1-Linux").
Including OS details in the agent capability simplifies implementation,
maintains backward compatibility, avoids introducing a new capability,
encourages adoption across Git-compatible software, and enhances
debugging by providing complete environment information without affecting
functionality. The operating system name is retrieved using the 'sysname'
field of the `uname(2)` system call or its equivalent.
However, there are differences between `uname(1)` (command-line utility)
and `uname(2)` (system call) outputs on Windows. These discrepancies
complicate testing on Windows platforms. For example:
- `uname(1)` output: MINGW64_NT-10.0-20348.3.4.10-87d57229.x86_64\
.2024-02-14.20:17.UTC.x86_64
- `uname(2)` output: Windows.10.0.20348
On Windows, uname(2) is not actually system-supplied but is instead
already faked up by Git itself. We could have overcome the test issue
on Windows by implementing a new `uname` subcommand in `test-tool`
using uname(2), but except uname(2), which would be tested against
itself, there would be nothing platform specific, so it's just simpler
to disable the tests on Windows.
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Usman Akinyemi <usmanakinyemi202@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git rev-list --missing=" learned to accept "print-info" that gives
known details expected of the missing objects, like path and type.
* jt/rev-list-missing-print-info:
rev-list: extend print-info to print missing object type
rev-list: add print-info action to print missing object path
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Lazy-loading missing files in a blobless clone on demand is costly
as it tends to be one-blob-at-a-time. "git backfill" is introduced
to help bulk-download necessary files beforehand.
* ds/backfill:
backfill: assume --sparse when sparse-checkout is enabled
backfill: add --sparse option
backfill: add --min-batch-size=<n> option
backfill: basic functionality and tests
backfill: add builtin boilerplate
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A previous commit introduced a "promisor.acceptFromServer" configuration
variable with only "None" or "All" as valid values.
Let's introduce "KnownName" and "KnownUrl" as valid values for this
configuration option to give more choice to a client about which
promisor remotes it might accept among those that the server advertised.
In case of "KnownName", the client will accept promisor remotes which
are already configured on the client and have the same name as those
advertised by the client. This could be useful in a corporate setup
where servers and clients are trusted to not switch names and URLs, but
where some kind of control is still useful.
In case of "KnownUrl", the client will accept promisor remotes which
have both the same name and the same URL configured on the client as the
name and URL advertised by the server. This is the most secure option,
so it should be used if possible.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a server S knows that some objects from a repository are available
from a promisor remote X, S might want to suggest to a client C cloning
or fetching the repo from S that C may use X directly instead of S for
these objects.
Note that this could happen both in the case S itself doesn't have the
objects and borrows them from X, and in the case S has the objects but
knows that X is better connected to the world (e.g., it is in a
$LARGEINTERNETCOMPANY datacenter with petabit/s backbone connections)
than S. Implementation of the latter case, which would require S to
omit in its response the objects available on X, is left for future
improvement though.
Then C might or might not, want to get the objects from X. If S and C
can agree on C using X directly, S can then omit objects that can be
obtained from X when answering C's request.
To allow S and C to agree and let each other know about C using X or
not, let's introduce a new "promisor-remote" capability in the
protocol v2, as well as a few new configuration variables:
- "promisor.advertise" on the server side, and:
- "promisor.acceptFromServer" on the client side.
By default, or if "promisor.advertise" is set to 'false', a server S will
not advertise the "promisor-remote" capability.
If S doesn't advertise the "promisor-remote" capability, then a client C
replying to S shouldn't advertise the "promisor-remote" capability
either.
If "promisor.advertise" is set to 'true', S will advertise its promisor
remotes with a string like:
promisor-remote=<pr-info>[;<pr-info>]...
where each <pr-info> element contains information about a single
promisor remote in the form:
name=<pr-name>[,url=<pr-url>]
where <pr-name> is the urlencoded name of a promisor remote and
<pr-url> is the urlencoded URL of the promisor remote named <pr-name>.
For now, the URL is passed in addition to the name. In the future, it
might be possible to pass other information like a filter-spec that the
client may use when cloning from S, or a token that the client may use
when retrieving objects from X.
It is C's responsibility to arrange how it can reach X though, so pieces
of information that are usually outside Git's concern, like proxy
configuration, must not be distributed over this protocol.
It might also be possible in the future for "promisor.advertise" to have
other values. For example a value like "onlyName" could prevent S from
advertising URLs, which could help in case C should use a different URL
for X than the URL S is using. (The URL S is using might be an internal
one on the server side for example.)
By default or if "promisor.acceptFromServer" is set to "None", C will
not accept to use the promisor remotes that might have been advertised
by S. In this case, C will not advertise any "promisor-remote"
capability in its reply to S.
If "promisor.acceptFromServer" is set to "All" and S advertised some
promisor remotes, then on the contrary, C will accept to use all the
promisor remotes that S advertised and C will reply with a string like:
promisor-remote=<pr-name>[;<pr-name>]...
where the <pr-name> elements are the urlencoded names of all the
promisor remotes S advertised.
In a following commit, other values for "promisor.acceptFromServer" will
be implemented, so that C will be able to decide the promisor remotes it
accepts depending on the name and URL it received from S. So even if
that name and URL information is not used much right now, it will be
needed soon.
Helped-by: Taylor Blau <me@ttaylorr.com>
Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The first line of a commit message is variously called 'title' or
'subject'.
Prefer 'title' unless discussing email.
Signed-off-by: M Hickford <mirth.hickford@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In the html documentation the link to the "OUTPUT" section is surrounded
by square brackets. Fix this by adding explicit link text to the cross
reference.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Acked-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a section for --stdin in the list of options and document that it
implies -z so readers know how to parse the output. Also correct the
merge status documentation for --stdin as if the status is less than
zero "git merge-tree" dies before printing it.
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Acked-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Explicitly set the default goal at the very top of various makefiles.
This is already present in some makefiles, but not all of them.
In particular, this corrects a regression introduced in a38edab7c8
(Makefile: generate doc versions via GIT-VERSION-GEN, 2024-12-06). That
commit added some config files as build targets for the Documentation
directory, and put the target configuration in a sensible place.
Unfortunately, that sensible place was above any other build target
definitions, meaning the default goal changed to being those
configuration files only, rather than the HTML and man page
documentation.
Signed-off-by: Adam Dinwoodie <adam@dinwoodie.org>
Helped-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Doc update.
* ps/doc-http-upload-archive-service:
doc: documentation for http.uploadarchive config option
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"git clone" learned to make a shallow clone for a single commit
that is not necessarily be at the tip of any branch.
* tc/clone-single-revision:
builtin/clone: teach git-clone(1) the --revision= option
parse-options: introduce die_for_incompatible_opt2()
clone: introduce struct clone_opts in builtin/clone.c
clone: add tags refspec earlier to fetch refspec
clone: refactor wanted_peer_refs()
clone: make it possible to specify --tags
clone: cut down on global variables in clone.c
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All the documentation .txt files have been renamed to .adoc to help
content aware editors.
* bc/doc-adoc-not-txt:
Remove obsolete ".txt" extensions for AsciiDoc files
doc: use .adoc extension for AsciiDoc files
gitattributes: mark AsciiDoc files as LF-only
editorconfig: add .adoc extension
doc: update gitignore for .adoc extension
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Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When 'remote.<name>.followRemoteHEAD' was added in b7f7d16562 (fetch:
add configuration for set_head behaviour, 2024-11-29), its description
was added to remote.txt in between the two paragraphs describing
'remote.<name>.serverOption'. Reunite these two paragraphs.
Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git -c help.autocorrect=0 psuh" shows the suggested typofix,
unlike the previous attempt in the base topic.
* da/help-autocorrect-one-fix:
help: add "show" as a valid configuration value
help: show the suggested command when help.autocorrect is false
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"[help] autocorrect = 1" used to be a way to say "please wait for
0.1 second after suggesting a typofix of the command name before
running that command"; now it means "yes, if there is a plausible
typofix for the command name, please run it immediately".
* sc/help-autocorrect-one:
help: interpret boolean string values for help.autocorrect
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Documentaiton updates.
* jp/doc-trailer-config:
config.txt: add trailer.* variables
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"git gc" learned the "--expire-to" option and passes it down to
underlying "git repack".
* zh/gc-expire-to:
gc: add `--expire-to` option
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"git pack-objects" and its wrapper "git repack" learned an option
to use an alternative path-hash function to improve delta-base
selection to produce a packfile with deeper history than window
size.
* ds/name-hash-tweaks:
pack-objects: prevent name hash version change
test-tool: add helper for name-hash values
p5313: add size comparison test
pack-objects: add GIT_TEST_NAME_HASH_VERSION
repack: add --name-hash-version option
pack-objects: add --name-hash-version option
pack-objects: create new name-hash function version
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The -X renormalize (or merge.renormalize config) option is intended to
reduce conflicts due to normalization of newer versions of history. It
does so by renormalizing files that it is about to do a three-way
content merge on. Some folks thought it would renormalize all files
throughout the tree, and the previous wording wasn't clear enough to
dispell that misconception. Update the docs to make it clear that the
merge machinery will only apply renormalization to files which need a
three-way content merge.
(Technically, the merge machinery also does renormalization on
modify/delete conflicts, in order to see if the modification was merely
a normalization; if so, it can accept the delete and not report a
conflict. But it's not clear that this piece needs to be explained to
users, and trying to distinguish it might feel like splitting hairs and
overcomplicating the explanation, so we leave it out.)
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We do not seem to centrally document exhaustively ways to spell
Boolean values.
The description in the Environment Variables of git(1) section
assumes that the reader is already familiar with how "Boolean valued
configuration variables" are specified, without referring to
anything, so there is no way for the readers to find out more.
The description of `bool` in the section on "--type
<type>" in "git config --help" might be the place to do so, but it
is not telling us all that much.
The description of Boolean valued placeholders in the pretty formats
section of "git log --help" enumerates the possible values with "etc."
implying there may be other synonyms; shrink the list of samples and
instead refer to the canonical and authoritative source of truth, which
now is git-config(1).
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In Git v2.44.0 support for 'git archive' over HTTP protocol
was added, but it was nowhere documented how it should be
enabled in git-http-backend.
Add missing documentation.
Signed-off-by: Piotr Szlazak <piotr.szlazak@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The git-clone(1) command has the option `--branch` that allows the user
to select the branch they want HEAD to point to. In a non-bare
repository this also checks out that branch.
Option `--branch` also accepts a tag. When a tag name is provided, the
commit this tag points to is checked out and HEAD is detached. Thus
`--branch` can be used to clone a repository and check out a ref kept
under `refs/heads` or `refs/tags`. But some other refs might be in use
as well. For example Git forges might use refs like `refs/pull/<id>` and
`refs/merge-requests/<id>` to track pull/merge requests. These refs
cannot be selected upon git-clone(1).
Add option `--revision` to git-clone(1). This option accepts a fully
qualified reference, or a hexadecimal commit ID. This enables the user
to clone and check out any revision they want. `--revision` can be used
in conjunction with `--depth` to do a minimal clone that only contains
the blob and tree for a single revision. This can be useful for
automated tests running in CI systems.
Using option `--branch` and `--single-branch` together is a similar
scenario, but serves a different purpose. Using these two options, a
singlet remote tracking branch is created and the fetch refspec is set
up so git-fetch(1) will receive updates on that branch from the remote.
This allows the user work on that single branch.
Option `--revision` on contrary detaches HEAD, creates no tracking
branches, and writes no fetch refspec.
Signed-off-by: Toon Claes <toon@iotcl.com>
Acked-by: Patrick Steinhardt <ps@pks.im>
[jc: removed unnecessary TEST_PASSES_SANITIZE_LEAK from the test]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Option --no-tags was added in 0dab2468ee (clone: add a --no-tags option
to clone without tags, 2017-04-26). At the time there was no need to
support --tags as well, although there was some conversation about
it[1].
To simplify the code and to prepare for future commits, invert the flag
internally. Functionally there is no change, because the flag is
default-enabled passing `--tags` has no effect, so there's no need to
add tests for this.
[1]: https://lore.kernel.org/git/CAGZ79kbHuMpiavJ90kQLEL_AR0BEyArcZoEWAjPPhOFacN16YQ@mail.gmail.com/
Signed-off-by: Toon Claes <toon@iotcl.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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0a01d41ee4 (http: add support for different sslcert and sslkey types.,
2023-03-20) added useful SSL config options, but did not document them.
Signed-off-by: Andrew Carter <andrew@emailcarter.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Additional information about missing objects found in git-rev-list(1)
can be printed by specifying the `print-info` missing action for the
`--missing` option. Extend this action to also print missing object type
information inferred from its containing object. This token follows the
form `type=<type>` and specifies the expected object type of the missing
object.
Signed-off-by: Justin Tobler <jltobler@gmail.com>
Acked-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Missing objects identified through git-rev-list(1) can be printed by
setting the `--missing=print` option. Additional information about the
missing object, such as its path and type, may be present in its
containing object.
Add the `print-info` missing action for the `--missing` option that,
when set, prints additional insight about the missing object inferred
from its containing object. Each line of output for a missing object is
in the form: `?<oid> [<token>=<value>]...`. The `<token>=<value>` pairs
containing additional information are separated from each other by a SP.
The value is encoded in a token specific fashion, but SP or LF contained
in value are always expected to be represented in such a way that the
resulting encoded value does not have either of these two problematic
bytes. This format is kept generic so it can be extended in the future
to support additional information.
For now, only a missing object path info is implemented. It follows the
form `path=<path>` and specifies the full path to the object from the
top-level tree. A path containing SP or special characters is enclosed
in double-quotes in the C style as needed. In a subsequent commit,
missing object type info will also be added.
Signed-off-by: Justin Tobler <jltobler@gmail.com>
Acked-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The previous change introduced the '--[no-]sparse' option for the 'git
backfill' command, but did not assume it as enabled by default. However,
this is likely the behavior that users will most often want to happen.
Without this default, users with a small sparse-checkout may be confused
when 'git backfill' downloads every version of every object in the full
history.
However, this is left as a separate change so this decision can be reviewed
independently of the value of the '--[no-]sparse' option.
Add a test of adding the '--sparse' option to a repo without sparse-checkout
to make it clear that supplying it without a sparse-checkout is an error.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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One way to significantly reduce the cost of a Git clone and later fetches is
to use a blobless partial clone and combine that with a sparse-checkout that
reduces the paths that need to be populated in the working directory. Not
only does this reduce the cost of clones and fetches, the sparse-checkout
reduces the number of objects needed to download from a promisor remote.
However, history investigations can be expensive as computing blob diffs
will trigger promisor remote requests for one object at a time. This can be
avoided by downloading the blobs needed for the given sparse-checkout using
'git backfill' and its new '--sparse' mode, at a time that the user is
willing to pay that extra cost.
Note that this is distinctly different from the '--filter=sparse:<oid>'
option, as this assumes that the partial clone has all reachable trees and
we are using client-side logic to avoid downloading blobs outside of the
sparse-checkout cone. This avoids the server-side cost of walking trees
while also achieving a similar goal. It also downloads in batches based on
similar path names, presenting a resumable download if things are
interrupted.
This augments the path-walk API to have a possibly-NULL 'pl' member that may
point to a 'struct pattern_list'. This could be more general than the
sparse-checkout definition at HEAD, but 'git backfill --sparse' is currently
the only consumer.
Be sure to test this in both cone mode and not cone mode. Cone mode has the
benefit that the path-walk can skip certain paths once they would expand
beyond the sparse-checkout. Non-cone mode can describe the included files
using both positive and negative patterns, which changes the possible return
values of path_matches_pattern_list(). Test both kinds of matches for
increased coverage.
To test this, we can create a blobless sparse clone, expand the
sparse-checkout slightly, and then run 'git backfill --sparse' to see
how much data is downloaded. The general steps are
1. git clone --filter=blob:none --sparse <url>
2. git sparse-checkout set <dir1> ... <dirN>
3. git backfill --sparse
For the Git repository with the 'builtin' directory in the
sparse-checkout, we get these results for various batch sizes:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|-------|
| (Initial clone) | 3 | 110 MB | |
| 10K | 12 | 192 MB | 17.2s |
| 15K | 9 | 192 MB | 15.5s |
| 20K | 8 | 192 MB | 15.5s |
| 25K | 7 | 192 MB | 14.7s |
This case matters less because a full clone of the Git repository from
GitHub is currently at 277 MB.
Using a copy of the Linux repository with the 'kernel/' directory in the
sparse-checkout, we get these results:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|------|
| (Initial clone) | 2 | 1,876 MB | |
| 10K | 11 | 2,187 MB | 46s |
| 25K | 7 | 2,188 MB | 43s |
| 50K | 5 | 2,194 MB | 44s |
| 100K | 4 | 2,194 MB | 48s |
This case is more meaningful because a full clone of the Linux
repository is currently over 6 GB, so this is a valuable way to download
a fraction of the repository and no longer need network access for all
reachable objects within the sparse-checkout.
Choosing a batch size will depend on a lot of factors, including the
user's network speed or reliability, the repository's file structure,
and how many versions there are of the file within the sparse-checkout
scope. There will not be a one-size-fits-all solution.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Users may want to specify a minimum batch size for their needs. This is only
a minimum: the path-walk API provides a list of OIDs that correspond to the
same path, and thus it is optimal to allow delta compression across those
objects in a single server request.
We could consider limiting the request to have a maximum batch size in the
future. For now, we let the path-walk API batches determine the
boundaries.
To get a feeling for the value of specifying the --min-batch-size parameter,
I tested a number of open source repositories available on GitHub. The
procedure was generally:
1. git clone --filter=blob:none <url>
2. git backfill
Checking the number of packfiles and the size of the .git/objects/pack
directory helps to identify the effects of different batch sizes.
For the Git repository, we get these results:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|-------|
| (Initial clone) | 2 | 119 MB | |
| 25K | 8 | 290 MB | 24s |
| 50K | 5 | 290 MB | 24s |
| 100K | 4 | 290 MB | 29s |
Other than the packfile counts decreasing as we need fewer batches, the
size and time required is not changing much for this small example.
For the nodejs/node repository, we see these results:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|--------|
| (Initial clone) | 2 | 330 MB | |
| 25K | 19 | 1,222 MB | 1m 22s |
| 50K | 11 | 1,221 MB | 1m 24s |
| 100K | 7 | 1,223 MB | 1m 40s |
| 250K | 4 | 1,224 MB | 2m 23s |
| 500K | 3 | 1,216 MB | 4m 38s |
Here, we don't have much difference in the size of the repo, though the
500K batch size results in a few MB gained. That comes at a cost of a
much longer time. This extra time is due to server-side delta
compression happening as the on-disk deltas don't appear to be reusable
all the time. But for smaller batch sizes, the server is able to find
reasonable deltas partly because we are asking for objects that appear
in the same region of the directory tree and include all versions of a
file at a specific path.
To contrast this example, I tested the microsoft/fluentui repo, which
has been known to have inefficient packing due to name hash collisions.
These results are found before GitHub had the opportunity to repack the
server with more advanced name hash versions:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|--------|
| (Initial clone) | 2 | 105 MB | |
| 5K | 53 | 348 MB | 2m 26s |
| 10K | 28 | 365 MB | 2m 22s |
| 15K | 19 | 407 MB | 2m 21s |
| 20K | 15 | 393 MB | 2m 28s |
| 25K | 13 | 417 MB | 2m 06s |
| 50K | 8 | 509 MB | 1m 34s |
| 100K | 5 | 535 MB | 1m 56s |
| 250K | 4 | 698 MB | 1m 33s |
| 500K | 3 | 696 MB | 1m 42s |
Here, a larger variety of batch sizes were chosen because of the great
variation in results. By asking the server to download small batches
corresponding to fewer paths at a time, the server is able to provide
better compression for these batches than it would for a regular clone.
A typical full clone for this repository would require 738 MB.
This example justifies the choice to batch requests by path name,
leading to improved communication with a server that is not optimally
packed.
Finally, the same experiment for the Linux repository had these results:
| Batch Size | Pack Count | Pack Size | Time |
|-----------------|------------|-----------|---------|
| (Initial clone) | 2 | 2,153 MB | |
| 25K | 63 | 6,380 MB | 14m 08s |
| 50K | 58 | 6,126 MB | 15m 11s |
| 100K | 30 | 6,135 MB | 18m 11s |
| 250K | 14 | 6,146 MB | 18m 22s |
| 500K | 8 | 6,143 MB | 33m 29s |
Even in this example, where the default name hash algorithm leads to
decent compression of the Linux kernel repository, there is value for
selecting a smaller batch size, to a limit. The 25K batch size has the
fastest time, but uses 250 MB more than the 50K batch size. The 500K
batch size took much more time due to server compression time and thus
we should avoid large batch sizes like this.
Based on these experiments, a batch size of 50,000 was chosen as the
default value.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The default behavior of 'git backfill' is to fetch all missing blobs that
are reachable from HEAD. Document and test this behavior.
The implementation is a very simple use of the path-walk API, initializing
the revision walk at HEAD to start the path-walk from all commits reachable
from HEAD. Ignore the object arrays that correspond to tree entries,
assuming that they are all present already.
The path-walk API provides lists of objects in batches according to a
common path, but that list could be very small. We want to balance the
number of requests to the server with the ability to have the process
interrupted with minimal repeated work to catch up in the next run.
Based on some experiments (detailed in the next change) a minimum batch
size of 50,000 is selected for the default.
This batch size is a _minimum_. As the path-walk API emits lists of blob
IDs, they are collected into a list of objects for a request to the
server. When that list is at least the minimum batch size, then the
request is sent to the server for the new objects. However, the list of
blob IDs from the path-walk API could be much longer than the batch
size. At this moment, it is unclear if there is a benefit to split the
list when there are too many objects at the same path.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In anticipation of implementing 'git backfill', populate the necessary files
with the boilerplate of a new builtin. Mark the builtin as experimental at
this time, allowing breaking changes in the near future, if necessary.
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add a literal value for showing the suggested autocorrection
for consistency with the rest of the help.autocorrect options.
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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