GITREMOTE-HELPERS(7)      (08/17/2021)       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 helpercqs standard
          input, and expects results from the helpercqs 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,

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          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 gitcqs native packfile protocol. This requires
                  a bidirectional, full-duplex connection.

                  Supported commands: connect.

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              stateless-connect
                  Experimental; for internal use only. Can attempt to
                  connect to a remote server for communication using
                  gitcqs 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 Gitcqs 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
                  gitcqs wire-protocol version 2. See the documentation
                  for the stateless-connect command for more
                  information.

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                  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. Itcqs 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

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                  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-importcqs
                  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-helpercqs stdin. It follows that Git
                  and fast-import are both connected to the
                  remote-helpercqs 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 helpercqs 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 helpercqs standard

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          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>

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              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 batchcqs 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.

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          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 helpercqs
              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 (cancqt connect, doncqt bother trying to

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              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 gitcqs
              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 (cancqt
              connect, doncqt 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.

          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

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              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.

              Deepens the history of a shallow repository based on
              time.

              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 doncqt 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

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              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.

              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)

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          git-fast-import(1)

     GIT
          Part of the git(1) suite

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