GITREMOTE-HELPERS(7) Git Manual GITREMOTE-HELPERS(7)

NAME

gitremote-helpers - Helper programs to interact with remote
repositories

SYNOPSIS

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.

get
Can use the get command to download a file from a given URI.

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 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 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 git-fast-
export(1).

signed-tags
This modifies the export capability, instructing Git to pass
--signed-tags=verbatim to 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 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.

get <uri> <path>
Downloads the file from the given <uri> to the given <path>. If
<path>.temp exists, then Git assumes that the .temp file is a
partial download from a previous attempt and will resume the
download from that position.

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.

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.

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
Indicate that the caller wants hash algorithm information to be
passed back from the remote. This mode is used when fetching
refs.

SEE ALSO

git-remote(1)

git-remote-ext(1)

git-remote-fd(1)

git-fast-import(1)

GIT

Part of the git(1) suite

Git 2.48.1 2025-01-13 GITREMOTE-HELPERS(7)