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git/Documentation/gitremote-helpers.txt

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gitremote-helpers(7)
====================
NAME
----
gitremote-helpers - Helper programs to interact with remote repositories
SYNOPSIS
--------
[verse]
'git remote-<transport>' <repository> [<URL>]
DESCRIPTION
-----------
Remote helper programs are normally not used directly by end users,
but they are invoked by Git when it needs to interact with remote
repositories Git does not support natively. A given helper will
implement a subset of the capabilities documented here. When Git
needs to interact with a repository using a remote helper, it spawns
the helper as an independent process, sends commands to the helper's
standard input, and expects results from the helper's standard
output. Because a remote helper runs as an independent process from
Git, there is no need to re-link Git to add a new helper, nor any
need to link the helper with the implementation of Git.
Every helper must support the "capabilities" command, which Git
uses to determine what other commands the helper will accept. Those
other commands can be used to discover and update remote refs,
transport objects between the object database and the remote repository,
and update the local object store.
Git comes with a "curl" family of remote helpers, that handle various
transport protocols, such as 'git-remote-http', 'git-remote-https',
'git-remote-ftp' and 'git-remote-ftps'. They implement the capabilities
'fetch', 'option', and 'push'.
INVOCATION
----------
Remote helper programs are invoked with one or (optionally) two
arguments. The first argument specifies a remote repository as in Git;
it is either the name of a configured remote or a URL. The second
argument specifies a URL; it is usually of the form
'<transport>://<address>', but any arbitrary string is possible.
The `GIT_DIR` environment variable is set up for the remote helper
and can be used to determine where to store additional data or from
which directory to invoke auxiliary Git commands.
When Git encounters a URL of the form '<transport>://<address>', where
'<transport>' is a protocol that it cannot handle natively, it
automatically invokes 'git remote-<transport>' with the full URL as
the second argument. If such a URL is encountered directly on the
command line, the first argument is the same as the second, and if it
is encountered in a configured remote, the first argument is the name
of that remote.
A URL of the form '<transport>::<address>' explicitly instructs Git to
invoke 'git remote-<transport>' with '<address>' as the second
argument. If such a URL is encountered directly on the command line,
the first argument is '<address>', and if it is encountered in a
configured remote, the first argument is the name of that remote.
Additionally, when a configured remote has `remote.<name>.vcs` set to
'<transport>', Git explicitly invokes 'git remote-<transport>' with
'<name>' as the first argument. If set, the second argument is
`remote.<name>.url`; otherwise, the second argument is omitted.
INPUT FORMAT
------------
Git sends the remote helper a list of commands on standard input, one
per line. The first command is always the 'capabilities' command, in
response to which the remote helper must print a list of the
capabilities it supports (see below) followed by a blank line. The
response to the capabilities command determines what commands Git uses
in the remainder of the command stream.
The command stream is terminated by a blank line. In some cases
(indicated in the documentation of the relevant commands), this blank
line is followed by a payload in some other protocol (e.g., the pack
protocol), while in others it indicates the end of input.
Capabilities
~~~~~~~~~~~~
Each remote helper is expected to support only a subset of commands.
The operations a helper supports are declared to Git in the response
to the `capabilities` command (see COMMANDS, below).
In the following, we list all defined capabilities and for
each we list which commands a helper with that capability
must provide.
Capabilities for Pushing
^^^^^^^^^^^^^^^^^^^^^^^^
'connect'::
Can attempt to connect to 'git receive-pack' (for pushing),
'git upload-pack', etc for communication using
git's native packfile protocol. This
requires a bidirectional, full-duplex connection.
+
Supported commands: 'connect'.
'stateless-connect'::
Experimental; for internal use only.
Can attempt to connect to a remote server for communication
using git's wire-protocol version 2. See the documentation
for the stateless-connect command for more information.
+
Supported commands: 'stateless-connect'.
'push'::
Can discover remote refs and push local commits and the
history leading up to them to new or existing remote refs.
+
Supported commands: 'list for-push', 'push'.
'export'::
Can discover remote refs and push specified objects from a
fast-import stream to remote refs.
+
Supported commands: 'list for-push', 'export'.
If a helper advertises 'connect', Git will use it if possible and
fall back to another capability if the helper requests so when
connecting (see the 'connect' command under COMMANDS).
When choosing between 'push' and 'export', Git prefers 'push'.
Other frontends may have some other order of preference.
'no-private-update'::
When using the 'refspec' capability, git normally updates the
private ref on successful push. This update is disabled when
the remote-helper declares the capability 'no-private-update'.
Capabilities for Fetching
^^^^^^^^^^^^^^^^^^^^^^^^^
'connect'::
Can try to connect to 'git upload-pack' (for fetching),
'git receive-pack', etc for communication using the
Git's native packfile protocol. This
requires a bidirectional, full-duplex connection.
+
Supported commands: 'connect'.
'stateless-connect'::
Experimental; for internal use only.
Can attempt to connect to a remote server for communication
using git's wire-protocol version 2. See the documentation
for the stateless-connect command for more information.
+
Supported commands: 'stateless-connect'.
'fetch'::
Can discover remote refs and transfer objects reachable from
them to the local object store.
+
Supported commands: 'list', 'fetch'.
'import'::
Can discover remote refs and output objects reachable from
them as a stream in fast-import format.
+
Supported commands: 'list', 'import'.
'check-connectivity'::
Can guarantee that when a clone is requested, the received
pack is self contained and is connected.
If a helper advertises 'connect', Git will use it if possible and
fall back to another capability if the helper requests so when
connecting (see the 'connect' command under COMMANDS).
When choosing between 'fetch' and 'import', Git prefers 'fetch'.
Other frontends may have some other order of preference.
Miscellaneous capabilities
^^^^^^^^^^^^^^^^^^^^^^^^^^
'option'::
For specifying settings like `verbosity` (how much output to
write to stderr) and `depth` (how much history is wanted in the
case of a shallow clone) that affect how other commands are
carried out.
'refspec' <refspec>::
For remote helpers that implement 'import' or 'export', this capability
allows the refs to be constrained to a private namespace, instead of
writing to refs/heads or refs/remotes directly.
It is recommended that all importers providing the 'import'
capability use this. It's mandatory for 'export'.
+
A helper advertising the capability
docs: stop using asciidoc no-inline-literal In asciidoc 7, backticks like `foo` produced a typographic effect, but did not otherwise affect the syntax. In asciidoc 8, backticks introduce an "inline literal" inside which markup is not interpreted. To keep compatibility with existing documents, asciidoc 8 has a "no-inline-literal" attribute to keep the old behavior. We enabled this so that the documentation could be built on either version. It has been several years now, and asciidoc 7 is no longer in wide use. We can now decide whether or not we want inline literals on their own merits, which are: 1. The source is much easier to read when the literal contains punctuation. You can use `master~1` instead of `master{tilde}1`. 2. They are less error-prone. Because of point (1), we tend to make mistakes and forget the extra layer of quoting. This patch removes the no-inline-literal attribute from the Makefile and converts every use of backticks in the documentation to an inline literal (they must be cleaned up, or the example above would literally show "{tilde}" in the output). Problematic sites were found by grepping for '`.*[{\\]' and examined and fixed manually. The results were then verified by comparing the output of "html2text" on the set of generated html pages. Doing so revealed that in addition to making the source more readable, this patch fixes several formatting bugs: - HTML rendering used the ellipsis character instead of literal "..." in code examples (like "git log A...B") - some code examples used the right-arrow character instead of '->' because they failed to quote - api-config.txt did not quote tilde, and the resulting HTML contained a bogus snippet like: <tt><sub></tt> foo <tt></sub>bar</tt> which caused some parsers to choke and omit whole sections of the page. - git-commit.txt confused ``foo`` (backticks inside a literal) with ``foo'' (matched double-quotes) - mentions of `A U Thor <author@example.com>` used to erroneously auto-generate a mailto footnote for author@example.com - the description of --word-diff=plain incorrectly showed the output as "[-removed-] and {added}", not "{+added+}". - using "prime" notation like: commit `C` and its replacement `C'` confused asciidoc into thinking that everything between the first backtick and the final apostrophe were meant to be inside matched quotes - asciidoc got confused by the escaping of some of our asterisks. In particular, `credential.\*` and `credential.<url>.\*` properly escaped the asterisk in the first case, but literally passed through the backslash in the second case. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
11 years ago
`refspec refs/heads/*:refs/svn/origin/branches/*`
is saying that, when it is asked to `import refs/heads/topic`, the
stream it outputs will update the `refs/svn/origin/branches/topic`
ref.
+
This capability can be advertised multiple times. The first
applicable refspec takes precedence. The left-hand of refspecs
advertised with this capability must cover all refs reported by
the list command. If no 'refspec' capability is advertised,
there is an implied `refspec *:*`.
+
When writing remote-helpers for decentralized version control
systems, it is advised to keep a local copy of the repository to
interact with, and to let the private namespace refs point to this
local repository, while the refs/remotes namespace is used to track
the remote repository.
'bidi-import'::
This modifies the 'import' capability.
The fast-import commands 'cat-blob' and 'ls' can be used by remote-helpers
to retrieve information about blobs and trees that already exist in
fast-import's memory. This requires a channel from fast-import to the
remote-helper.
If it is advertised in addition to "import", Git establishes a pipe from
fast-import to the remote-helper's stdin.
It follows that Git and fast-import are both connected to the
remote-helper's stdin. Because Git can send multiple commands to
the remote-helper it is required that helpers that use 'bidi-import'
buffer all 'import' commands of a batch before sending data to fast-import.
This is to prevent mixing commands and fast-import responses on the
helper's stdin.
'export-marks' <file>::
This modifies the 'export' capability, instructing Git to dump the
internal marks table to <file> when complete. For details,
read up on `--export-marks=<file>` in linkgit:git-fast-export[1].
'import-marks' <file>::
This modifies the 'export' capability, instructing Git to load the
marks specified in <file> before processing any input. For details,
read up on `--import-marks=<file>` in linkgit:git-fast-export[1].
'signed-tags'::
This modifies the 'export' capability, instructing Git to pass
`--signed-tags=verbatim` to linkgit:git-fast-export[1]. In the
absence of this capability, Git will use `--signed-tags=warn-strip`.
'object-format'::
This indicates that the helper is able to interact with the remote
side using an explicit hash algorithm extension.
COMMANDS
--------
Commands are given by the caller on the helper's standard input, one per line.
'capabilities'::
Lists the capabilities of the helper, one per line, ending
with a blank line. Each capability may be preceded with '*',
which marks them mandatory for Git versions using the remote
helper to understand. Any unknown mandatory capability is a
fatal error.
+
Support for this command is mandatory.
'list'::
Lists the refs, one per line, in the format "<value> <name>
[<attr> ...]". The value may be a hex sha1 hash, "@<dest>" for
a symref, ":<keyword> <value>" for a key-value pair, or
"?" to indicate that the helper could not get the value of the
ref. A space-separated list of attributes follows the name;
unrecognized attributes are ignored. The list ends with a
blank line.
+
See REF LIST ATTRIBUTES for a list of currently defined attributes.
See REF LIST KEYWORDS for a list of currently defined keywords.
+
Supported if the helper has the "fetch" or "import" capability.
'list for-push'::
Similar to 'list', except that it is used if and only if
the caller wants to the resulting ref list to prepare
push commands.
A helper supporting both push and fetch can use this
to distinguish for which operation the output of 'list'
is going to be used, possibly reducing the amount
of work that needs to be performed.
+
Supported if the helper has the "push" or "export" capability.
'option' <name> <value>::
Sets the transport helper option <name> to <value>. Outputs a
single line containing one of 'ok' (option successfully set),
'unsupported' (option not recognized) or 'error <msg>'
(option <name> is supported but <value> is not valid
for it). Options should be set before other commands,
and may influence the behavior of those commands.
+
See OPTIONS for a list of currently defined options.
+
Supported if the helper has the "option" capability.
'fetch' <sha1> <name>::
Fetches the given object, writing the necessary objects
to the database. Fetch commands are sent in a batch, one
per line, terminated with a blank line.
Outputs a single blank line when all fetch commands in the
same batch are complete. Only objects which were reported
in the output of 'list' with a sha1 may be fetched this way.
+
Optionally may output a 'lock <file>' line indicating the full path of
a file under `$GIT_DIR/objects/pack` which is keeping a pack until
refs can be suitably updated. The path must end with `.keep`. This is
a mechanism to name a <pack,idx,keep> tuple by giving only the keep
component. The kept pack will not be deleted by a concurrent repack,
even though its objects may not be referenced until the fetch completes.
The `.keep` file will be deleted at the conclusion of the fetch.
+
If option 'check-connectivity' is requested, the helper must output
'connectivity-ok' if the clone is self-contained and connected.
+
Supported if the helper has the "fetch" capability.
'push' +<src>:<dst>::
Pushes the given local <src> commit or branch to the
remote branch described by <dst>. A batch sequence of
one or more 'push' commands is terminated with a blank line
(if there is only one reference to push, a single 'push' command
is followed by a blank line). For example, the following would
be two batches of 'push', the first asking the remote-helper
to push the local ref 'master' to the remote ref 'master' and
the local `HEAD` to the remote 'branch', and the second
asking to push ref 'foo' to ref 'bar' (forced update requested
by the '+').
+
------------
push refs/heads/master:refs/heads/master
push HEAD:refs/heads/branch
\n
push +refs/heads/foo:refs/heads/bar
\n
------------
+
Zero or more protocol options may be entered after the last 'push'
command, before the batch's terminating blank line.
+
When the push is complete, outputs one or more 'ok <dst>' or
'error <dst> <why>?' lines to indicate success or failure of
each pushed ref. The status report output is terminated by
a blank line. The option field <why> may be quoted in a C
style string if it contains an LF.
+
Supported if the helper has the "push" capability.
'import' <name>::
Produces a fast-import stream which imports the current value
of the named ref. It may additionally import other refs as
needed to construct the history efficiently. The script writes
to a helper-specific private namespace. The value of the named
ref should be written to a location in this namespace derived
by applying the refspecs from the "refspec" capability to the
name of the ref.
+
Especially useful for interoperability with a foreign versioning
system.
+
Just like 'push', a batch sequence of one or more 'import' is
terminated with a blank line. For each batch of 'import', the remote
helper should produce a fast-import stream terminated by a 'done'
command.
+
Note that if the 'bidi-import' capability is used the complete batch
sequence has to be buffered before starting to send data to fast-import
to prevent mixing of commands and fast-import responses on the helper's
stdin.
+
Supported if the helper has the "import" capability.
'export'::
Instructs the remote helper that any subsequent input is
part of a fast-import stream (generated by 'git fast-export')
containing objects which should be pushed to the remote.
+
Especially useful for interoperability with a foreign versioning
system.
+
The 'export-marks' and 'import-marks' capabilities, if specified,
affect this command in so far as they are passed on to 'git
fast-export', which then will load/store a table of marks for
local objects. This can be used to implement for incremental
operations.
+
Supported if the helper has the "export" capability.
'connect' <service>::
Connects to given service. Standard input and standard output
of helper are connected to specified service (git prefix is
included in service name so e.g. fetching uses 'git-upload-pack'
as service) on remote side. Valid replies to this command are
empty line (connection established), 'fallback' (no smart
transport support, fall back to dumb transports) and just
exiting with error message printed (can't connect, don't
bother trying to fall back). After line feed terminating the
positive (empty) response, the output of service starts. After
the connection ends, the remote helper exits.
+
Supported if the helper has the "connect" capability.
'stateless-connect' <service>::
Experimental; for internal use only.
Connects to the given remote service for communication using
git's wire-protocol version 2. Valid replies to this command
are empty line (connection established), 'fallback' (no smart
transport support, fall back to dumb transports) and just
exiting with error message printed (can't connect, don't bother
trying to fall back). After line feed terminating the positive
(empty) response, the output of the service starts. Messages
(both request and response) must consist of zero or more
stateless-connect: send response end packet Currently, remote-curl acts as a proxy and blindly forwards packets between an HTTP server and fetch-pack. In the case of a stateless RPC connection where the connection is terminated before the transaction is complete, remote-curl will blindly forward the packets before waiting on more input from fetch-pack. Meanwhile, fetch-pack will read the transaction and continue reading, expecting more input to continue the transaction. This results in a deadlock between the two processes. This can be seen in the following command which does not terminate: $ git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012 Cloning into 'git'... whereas the v1 version does terminate as expected: $ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=20151012 Cloning into 'git'... fatal: the remote end hung up unexpectedly Instead of blindly forwarding packets, make remote-curl insert a response end packet after proxying the responses from the remote server when using stateless_connect(). On the RPC client side, ensure that each response ends as described. A separate control packet is chosen because we need to be able to differentiate between what the remote server sends and remote-curl's control packets. By ensuring in the remote-curl code that a server cannot send response end packets, we prevent a malicious server from being able to perform a denial of service attack in which they spoof a response end packet and cause the described deadlock to happen. Reported-by: Force Charlie <charlieio@outlook.com> Helped-by: Jeff King <peff@peff.net> Signed-off-by: Denton Liu <liu.denton@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
3 years ago
PKT-LINEs, terminating in a flush packet. Response messages will
then have a response end packet after the flush packet to
indicate the end of a response. The client must not
expect the server to store any state in between request-response
pairs. After the connection ends, the remote helper exits.
+
Supported if the helper has the "stateless-connect" capability.
If a fatal error occurs, the program writes the error message to
stderr and exits. The caller should expect that a suitable error
message has been printed if the child closes the connection without
completing a valid response for the current command.
Additional commands may be supported, as may be determined from
capabilities reported by the helper.
REF LIST ATTRIBUTES
-------------------
The 'list' command produces a list of refs in which each ref
may be followed by a list of attributes. The following ref list
attributes are defined.
'unchanged'::
This ref is unchanged since the last import or fetch, although
the helper cannot necessarily determine what value that produced.
REF LIST KEYWORDS
-----------------
The 'list' command may produce a list of key-value pairs.
The following keys are defined.
'object-format'::
The refs are using the given hash algorithm. This keyword is only
used if the server and client both support the object-format
extension.
OPTIONS
-------
The following options are defined and (under suitable circumstances)
set by Git if the remote helper has the 'option' capability.
'option verbosity' <n>::
Changes the verbosity of messages displayed by the helper.
A value of 0 for <n> means that processes operate
quietly, and the helper produces only error output.
1 is the default level of verbosity, and higher values
of <n> correspond to the number of -v flags passed on the
command line.
'option progress' {'true'|'false'}::
Enables (or disables) progress messages displayed by the
transport helper during a command.
'option depth' <depth>::
Deepens the history of a shallow repository.
'option deepen-since <timestamp>::
Deepens the history of a shallow repository based on time.
'option deepen-not <ref>::
Deepens the history of a shallow repository excluding ref.
Multiple options add up.
fetch, upload-pack: --deepen=N extends shallow boundary by N commits In git-fetch, --depth argument is always relative with the latest remote refs. This makes it a bit difficult to cover this use case, where the user wants to make the shallow history, say 3 levels deeper. It would work if remote refs have not moved yet, but nobody can guarantee that, especially when that use case is performed a couple months after the last clone or "git fetch --depth". Also, modifying shallow boundary using --depth does not work well with clones created by --since or --not. This patch fixes that. A new argument --deepen=<N> will add <N> more (*) parent commits to the current history regardless of where remote refs are. Have/Want negotiation is still respected. So if remote refs move, the server will send two chunks: one between "have" and "want" and another to extend shallow history. In theory, the client could send no "want"s in order to get the second chunk only. But the protocol does not allow that. Either you send no want lines, which means ls-remote; or you have to send at least one want line that carries deep-relative to the server.. The main work was done by Dongcan Jiang. I fixed it up here and there. And of course all the bugs belong to me. (*) We could even support --deepen=<N> where <N> is negative. In that case we can cut some history from the shallow clone. This operation (and --depth=<shorter depth>) does not require interaction with remote side (and more complicated to implement as a result). Helped-by: Duy Nguyen <pclouds@gmail.com> Helped-by: Eric Sunshine <sunshine@sunshineco.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Dongcan Jiang <dongcan.jiang@gmail.com> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
7 years ago
'option deepen-relative {'true'|'false'}::
Deepens the history of a shallow repository relative to
current boundary. Only valid when used with "option depth".
'option followtags' {'true'|'false'}::
If enabled the helper should automatically fetch annotated
tag objects if the object the tag points at was transferred
during the fetch command. If the tag is not fetched by
the helper a second fetch command will usually be sent to
ask for the tag specifically. Some helpers may be able to
use this option to avoid a second network connection.
'option dry-run' {'true'|'false'}:
If true, pretend the operation completed successfully,
but don't actually change any repository data. For most
helpers this only applies to the 'push', if supported.
'option servpath <c-style-quoted-path>'::
Sets service path (--upload-pack, --receive-pack etc.) for
next connect. Remote helper may support this option, but
must not rely on this option being set before
connect request occurs.
'option check-connectivity' {'true'|'false'}::
Request the helper to check connectivity of a clone.
'option force' {'true'|'false'}::
Request the helper to perform a force update. Defaults to
'false'.
'option cloning' {'true'|'false'}::
Notify the helper this is a clone request (i.e. the current
repository is guaranteed empty).
'option update-shallow' {'true'|'false'}::
Allow to extend .git/shallow if the new refs require it.
'option pushcert' {'true'|'false'}::
GPG sign pushes.
'option push-option <string>::
Transmit <string> as a push option. As the push option
must not contain LF or NUL characters, the string is not encoded.
'option from-promisor' {'true'|'false'}::
Indicate that these objects are being fetched from a promisor.
'option no-dependents' {'true'|'false'}::
Indicate that only the objects wanted need to be fetched, not
their dependents.
remote-curl: pass on atomic capability to remote side When pushing more than one reference with the --atomic option, the server is supposed to perform a single atomic transaction to update the references, leaving them either all to succeed or all to fail. This works fine when pushing locally or over SSH, but when pushing over HTTP, we fail to pass the atomic capability to the remote side. In fact, we have not reported this capability to any remote helpers during the life of the feature. Now normally, things happen to work nevertheless, since we actually check for most types of failures, such as non-fast-forward updates, on the client side, and just abort the entire attempt. However, if the server side reports a problem, such as the inability to lock a ref, the transaction isn't atomic, because we haven't passed the appropriate capability over and the remote side has no way of knowing that we wanted atomic behavior. Fix this by passing the option from the transport code through to remote helpers, and from the HTTP remote helper down to send-pack. With this change, we can detect if the server side rejects the push and report back appropriately. Note the difference in the messages: the remote side reports "atomic transaction failed", while our own checking rejects pushes with the message "atomic push failed". Document the atomic option in the remote helper documentation, so other implementers can implement it if they like. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
3 years ago
'option atomic' {'true'|'false'}::
When pushing, request the remote server to update refs in a single atomic
transaction. If successful, all refs will be updated, or none will. If the
remote side does not support this capability, the push will fail.
'option object-format' {'true'|algorithm}::
If 'true', indicate that the caller wants hash algorithm information
to be passed back from the remote. This mode is used when fetching
refs.
+
If set to an algorithm, indicate that the caller wants to interact with
the remote side using that algorithm.
SEE ALSO
--------
linkgit:git-remote[1]
linkgit:git-remote-ext[1]
linkgit:git-remote-fd[1]
linkgit:git-fast-import[1]
GIT
---
Part of the linkgit:git[1] suite