Documentation/gitremote-helpers.txt - jrn/git - Git at Google

 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
 `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`.


 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, 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.
 +
 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. 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.

 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.

 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
	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
	`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`.



	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, 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.
	+
	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. 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.

	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.

	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