gitremote-helpers - Helper programs to interact with remote
repositories
git remote-<transport> <repository> [<URL>]
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.
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.
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.
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 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.
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.
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.
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.
git-remote(1)
git-remote-ext(1)
git-remote-fd(1)
git-fast-import(1)