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|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
git-remote(1)
git-remote-ext(1)
git-remote-fd(1)
git-fast-import(1)
GIT
Part of the git(1) suite
Git 2.38.0 10/02/2022 gitremote-helpers(7)
git 2.38.0 - Generated Tue Oct 4 12:49:45 CDT 2022