gitprotocol-v2(category16-debian.html) - phpMan

GITPROTOCOL-V2(5)                 Git Manual                 GITPROTOCOL-V2(5)
NAME
       gitprotocol-v2 - Git Wire Protocol, Version 2
SYNOPSIS
       <over-the-wire-protocol>
DESCRIPTION
       This document presents a specification for a version 2 of Git's wire
       protocol. Protocol v2 will improve upon v1 in the following ways:
       o   Instead of multiple service names, multiple commands will be
           supported by a single service
       o   Easily extendable as capabilities are moved into their own section
           of the protocol, no longer being hidden behind a NUL byte and
           limited by the size of a pkt-line
       o   Separate out other information hidden behind NUL bytes (e.g. agent
           string as a capability and symrefs can be requested using ls-refs)
       o   Reference advertisement will be omitted unless explicitly requested
       o   ls-refs command to explicitly request some refs
       o   Designed with http and stateless-rpc in mind. With clear flush
           semantics the http remote helper can simply act as a proxy
       In protocol v2 communication is command oriented. When first contacting
       a server a list of capabilities will be advertised. Some of these
       capabilities will be commands which a client can request be executed.
       Once a command has completed, a client can reuse the connection and
       request that other commands be executed.
PACKET-LINE FRAMING
       All communication is done using packet-line framing, just as in v1. See
       gitprotocol-pack(5) and gitprotocol-common(5) for more information.
       In protocol v2 these special packets will have the following semantics:
       o   0000 Flush Packet (flush-pkt) - indicates the end of a message
       o   0001 Delimiter Packet (delim-pkt) - separates sections of a message
       o   0002 Response End Packet (response-end-pkt) - indicates the end of
           a response for stateless connections
INITIAL CLIENT REQUEST
       In general a client can request to speak protocol v2 by sending
       version=2 through the respective side-channel for the transport being
       used which inevitably sets GIT_PROTOCOL. More information can be found
       in gitprotocol-pack(5) and gitprotocol-http(5), as well as the
       GIT_PROTOCOL definition in git.txt. In all cases the response from the
       server is the capability advertisement.
   Git Transport
       When using the git:// transport, you can request to use protocol v2 by
       sending "version=2" as an extra parameter:
           003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0
   SSH and File Transport
       When using either the ssh:// or file:// transport, the GIT_PROTOCOL
       environment variable must be set explicitly to include "version=2". The
       server may need to be configured to allow this environment variable to
       pass.
   HTTP Transport
       When using the http:// or https:// transport a client makes a "smart"
       info/refs request as described in gitprotocol-http(5) and requests that
       v2 be used by supplying "version=2" in the Git-Protocol header.
           C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0
           C: Git-Protocol: version=2
       A v2 server would reply:
           S: 200 OK
           S: <Some headers>
           S: ...
           S:
           S: 000eversion 2\n
           S: <capability-advertisement>
       Subsequent requests are then made directly to the service
       $GIT_URL/git-upload-pack. (This works the same for git-receive-pack).
       Uses the --http-backend-info-refs option to git-upload-pack(1).
       The server may need to be configured to pass this header's contents via
       the GIT_PROTOCOL variable. See the discussion in git-http-backend.txt.
CAPABILITY ADVERTISEMENT
       A server which decides to communicate (based on a request from a
       client) using protocol version 2, notifies the client by sending a
       version string in its initial response followed by an advertisement of
       its capabilities. Each capability is a key with an optional value.
       Clients must ignore all unknown keys. Semantics of unknown values are
       left to the definition of each key. Some capabilities will describe
       commands which can be requested to be executed by the client.
           capability-advertisement = protocol-version
                                      capability-list
                                      flush-pkt
           protocol-version = PKT-LINE("version 2" LF)
           capability-list = *capability
           capability = PKT-LINE(key[=value] LF)
           key = 1*(ALPHA | DIGIT | "-_")
           value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()<>!@#$%^&*+=:;")
COMMAND REQUEST
       After receiving the capability advertisement, a client can then issue a
       request to select the command it wants with any particular capabilities
       or arguments. There is then an optional section where the client can
       provide any command specific parameters or queries. Only a single
       command can be requested at a time.
           request = empty-request | command-request
           empty-request = flush-pkt
           command-request = command
                             capability-list
                             delim-pkt
                             command-args
                             flush-pkt
           command = PKT-LINE("command=" key LF)
           command-args = *command-specific-arg
           command-specific-args are packet line framed arguments defined by
           each individual command.
       The server will then check to ensure that the client's request is
       comprised of a valid command as well as valid capabilities which were
       advertised. If the request is valid the server will then execute the
       command. A server MUST wait till it has received the client's entire
       request before issuing a response. The format of the response is
       determined by the command being executed, but in all cases a flush-pkt
       indicates the end of the response.
       When a command has finished, and the client has received the entire
       response from the server, a client can either request that another
       command be executed or can terminate the connection. A client may
       optionally send an empty request consisting of just a flush-pkt to
       indicate that no more requests will be made.
CAPABILITIES
       There are two different types of capabilities: normal capabilities,
       which can be used to convey information or alter the behavior of a
       request, and commands, which are the core actions that a client wants
       to perform (fetch, push, etc).
       Protocol version 2 is stateless by default. This means that all
       commands must only last a single round and be stateless from the
       perspective of the server side, unless the client has requested a
       capability indicating that state should be maintained by the server.
       Clients MUST NOT require state management on the server side in order
       to function correctly. This permits simple round-robin load-balancing
       on the server side, without needing to worry about state management.
   agent
       The server can advertise the agent capability with a value X (in the
       form agent=X) to notify the client that the server is running version
       X. The client may optionally send its own agent string by including the
       agent capability with a value Y (in the form agent=Y) in its request to
       the server (but it MUST NOT do so if the server did not advertise the
       agent capability). The X and Y strings may contain any printable ASCII
       characters except space (i.e., the byte range 32 < x < 127), and are
       typically of the form "package/version" (e.g., "git/1.8.3.1"). The
       agent strings are purely informative for statistics and debugging
       purposes, and MUST NOT be used to programmatically assume the presence
       or absence of particular features.
   ls-refs
       ls-refs is the command used to request a reference advertisement in v2.
       Unlike the current reference advertisement, ls-refs takes in arguments
       which can be used to limit the refs sent from the server.
       Additional features not supported in the base command will be
       advertised as the value of the command in the capability advertisement
       in the form of a space separated list of features: "<command>=<feature
       1> <feature 2>"
       ls-refs takes in the following arguments:
           symrefs
               In addition to the object pointed by it, show the underlying ref
               pointed by it when showing a symbolic ref.
           peel
               Show peeled tags.
           ref-prefix <prefix>
               When specified, only references having a prefix matching one of
               the provided prefixes are displayed. Multiple instances may be
               given, in which case references matching any prefix will be
               shown. Note that this is purely for optimization; a server MAY
               show refs not matching the prefix if it chooses, and clients
               should filter the result themselves.
       If the unborn feature is advertised the following argument can be
       included in the client's request.
           unborn
               The server will send information about HEAD even if it is a symref
               pointing to an unborn branch in the form "unborn HEAD
               symref-target:<target>".
       The output of ls-refs is as follows:
           output = *ref
                    flush-pkt
           obj-id-or-unborn = (obj-id | "unborn")
           ref = PKT-LINE(obj-id-or-unborn SP refname *(SP ref-attribute) LF)
           ref-attribute = (symref | peeled)
           symref = "symref-target:" symref-target
           peeled = "peeled:" obj-id
   fetch
       fetch is the command used to fetch a packfile in v2. It can be looked
       at as a modified version of the v1 fetch where the ref-advertisement is
       stripped out (since the ls-refs command fills that role) and the
       message format is tweaked to eliminate redundancies and permit easy
       addition of future extensions.
       Additional features not supported in the base command will be
       advertised as the value of the command in the capability advertisement
       in the form of a space separated list of features: "<command>=<feature
       1> <feature 2>"
       A fetch request can take the following arguments:
           want <oid>
               Indicates to the server an object which the client wants to
               retrieve.  Wants can be anything and are not limited to
               advertised objects.
           have <oid>
               Indicates to the server an object which the client has locally.
               This allows the server to make a packfile which only contains
               the objects that the client needs. Multiple 'have' lines can be
               supplied.
           done
               Indicates to the server that negotiation should terminate (or
               not even begin if performing a clone) and that the server should
               use the information supplied in the request to construct the
               packfile.
           thin-pack
               Request that a thin pack be sent, which is a pack with deltas
               which reference base objects not contained within the pack (but
               are known to exist at the receiving end). This can reduce the
               network traffic significantly, but it requires the receiving end
               to know how to "thicken" these packs by adding the missing bases
               to the pack.
           no-progress
               Request that progress information that would normally be sent on
               side-band channel 2, during the packfile transfer, should not be
               sent.  However, the side-band channel 3 is still used for error
               responses.
           include-tag
               Request that annotated tags should be sent if the objects they
               point to are being sent.
           ofs-delta
               Indicate that the client understands PACKv2 with delta referring
               to its base by position in pack rather than by an oid.  That is,
               they can read OBJ_OFS_DELTA (aka type 6) in a packfile.
       If the shallow feature is advertised the following arguments can be
       included in the clients request as well as the potential addition of
       the shallow-info section in the server's response as explained below.
           shallow <oid>
               A client must notify the server of all commits for which it only
               has shallow copies (meaning that it doesn't have the parents of
               a commit) by supplying a 'shallow <oid>' line for each such
               object so that the server is aware of the limitations of the
               client's history.  This is so that the server is aware that the
               client may not have all objects reachable from such commits.
           deepen <depth>
               Requests that the fetch/clone should be shallow having a commit
               depth of <depth> relative to the remote side.
           deepen-relative
               Requests that the semantics of the "deepen" command be changed
               to indicate that the depth requested is relative to the client's
               current shallow boundary, instead of relative to the requested
               commits.
           deepen-since <timestamp>
               Requests that the shallow clone/fetch should be cut at a
               specific time, instead of depth.  Internally it's equivalent to
               doing "git rev-list --max-age=<timestamp>". Cannot be used with
               "deepen".
           deepen-not <rev>
               Requests that the shallow clone/fetch should be cut at a
               specific revision specified by '<rev>', instead of a depth.
               Internally it's equivalent of doing "git rev-list --not <rev>".
               Cannot be used with "deepen", but can be used with
               "deepen-since".
       If the filter feature is advertised, the following argument can be
       included in the client's request:
           filter <filter-spec>
               Request that various objects from the packfile be omitted
               using one of several filtering techniques. These are intended
               for use with partial clone and partial fetch operations. See
               `rev-list` for possible "filter-spec" values. When communicating
               with other processes, senders SHOULD translate scaled integers
               (e.g. "1k") into a fully-expanded form (e.g. "1024") to aid
               interoperability with older receivers that may not understand
               newly-invented scaling suffixes. However, receivers SHOULD
               accept the following suffixes: 'k', 'm', and 'g' for 1024,
               1048576, and 1073741824, respectively.
       If the ref-in-want feature is advertised, the following argument can be
       included in the client's request as well as the potential addition of
       the wanted-refs section in the server's response as explained below.
           want-ref <ref>
               Indicates to the server that the client wants to retrieve a
               particular ref, where <ref> is the full name of a ref on the
               server.
       If the sideband-all feature is advertised, the following argument can
       be included in the client's request:
           sideband-all
               Instruct the server to send the whole response multiplexed, not just
               the packfile section. All non-flush and non-delim PKT-LINE in the
               response (not only in the packfile section) will then start with a byte
               indicating its sideband (1, 2, or 3), and the server may send "0005\2"
               (a PKT-LINE of sideband 2 with no payload) as a keepalive packet.
       If the packfile-uris feature is advertised, the following argument can
       be included in the client's request as well as the potential addition
       of the packfile-uris section in the server's response as explained
       below.
           packfile-uris <comma-separated list of protocols>
               Indicates to the server that the client is willing to receive
               URIs of any of the given protocols in place of objects in the
               sent packfile. Before performing the connectivity check, the
               client should download from all given URIs. Currently, the
               protocols supported are "http" and "https".
       If the wait-for-done feature is advertised, the following argument can
       be included in the client's request.
           wait-for-done
               Indicates to the server that it should never send "ready", but
               should wait for the client to say "done" before sending the
               packfile.
       The response of fetch is broken into a number of sections separated by
       delimiter packets (0001), with each section beginning with its section
       header. Most sections are sent only when the packfile is sent.
           output = acknowledgements flush-pkt |
                    [acknowledgments delim-pkt] [shallow-info delim-pkt]
                    [wanted-refs delim-pkt] [packfile-uris delim-pkt]
                    packfile flush-pkt
           acknowledgments = PKT-LINE("acknowledgments" LF)
                             (nak | *ack)
                             (ready)
           ready = PKT-LINE("ready" LF)
           nak = PKT-LINE("NAK" LF)
           ack = PKT-LINE("ACK" SP obj-id LF)
           shallow-info = PKT-LINE("shallow-info" LF)
                          *PKT-LINE((shallow | unshallow) LF)
           shallow = "shallow" SP obj-id
           unshallow = "unshallow" SP obj-id
           wanted-refs = PKT-LINE("wanted-refs" LF)
                         *PKT-LINE(wanted-ref LF)
           wanted-ref = obj-id SP refname
           packfile-uris = PKT-LINE("packfile-uris" LF) *packfile-uri
           packfile-uri = PKT-LINE(40*(HEXDIGIT) SP *%x20-ff LF)
           packfile = PKT-LINE("packfile" LF)
                      *PKT-LINE(%x01-03 *%x00-ff)
           acknowledgments section
               * If the client determines that it is finished with negotiations by
                 sending a "done" line (thus requiring the server to send a packfile),
                 the acknowledgments sections MUST be omitted from the server's
                 response.
       o   Always begins with the section header "acknowledgments"
       o   The server will respond with "NAK" if none of the object ids sent
           as have lines were common.
       o   The server will respond with "ACK obj-id" for all of the object ids
           sent as have lines which are common.
       o   A response cannot have both "ACK" lines as well as a "NAK" line.
       o   The server will respond with a "ready" line indicating that the
           server has found an acceptable common base and is ready to make and
           send a packfile (which will be found in the packfile section of the
           same response)
       o   If the server has found a suitable cut point and has decided to
           send a "ready" line, then the server can decide to (as an
           optimization) omit any "ACK" lines it would have sent during its
           response. This is because the server will have already determined
           the objects it plans to send to the client and no further
           negotiation is needed.
               shallow-info section
                   * If the client has requested a shallow fetch/clone, a shallow
                     client requests a fetch or the server is shallow then the
                     server's response may include a shallow-info section.  The
                     shallow-info section will be included if (due to one of the
                     above conditions) the server needs to inform the client of any
                     shallow boundaries or adjustments to the clients already
                     existing shallow boundaries.
       o   Always begins with the section header "shallow-info"
       o   If a positive depth is requested, the server will compute the set
           of commits which are no deeper than the desired depth.
       o   The server sends a "shallow obj-id" line for each commit whose
           parents will not be sent in the following packfile.
       o   The server sends an "unshallow obj-id" line for each commit which
           the client has indicated is shallow, but is no longer shallow as a
           result of the fetch (due to its parents being sent in the following
           packfile).
       o   The server MUST NOT send any "unshallow" lines for anything which
           the client has not indicated was shallow as a part of its request.
               wanted-refs section
                   * This section is only included if the client has requested a
                     ref using a 'want-ref' line and if a packfile section is also
                     included in the response.
       o   Always begins with the section header "wanted-refs".
       o   The server will send a ref listing ("<oid> <refname>") for each
           reference requested using want-ref lines.
       o   The server MUST NOT send any refs which were not requested using
           want-ref lines.
               packfile-uris section
                   * This section is only included if the client sent
                     'packfile-uris' and the server has at least one such URI to
                     send.
       o   Always begins with the section header "packfile-uris".
       o   For each URI the server sends, it sends a hash of the pack's
           contents (as output by git index-pack) followed by the URI.
       o   The hashes are 40 hex characters long. When Git upgrades to a new
           hash algorithm, this might need to be updated. (It should match
           whatever index-pack outputs after "pack\t" or "keep\t".
               packfile section
                   * This section is only included if the client has sent 'want'
                     lines in its request and either requested that no more
                     negotiation be done by sending 'done' or if the server has
                     decided it has found a sufficient cut point to produce a
                     packfile.
       o   Always begins with the section header "packfile"
       o   The transmission of the packfile begins immediately after the
           section header
       o   The data transfer of the packfile is always multiplexed, using the
           same semantics of the side-band-64k capability from protocol
           version 1. This means that each packet, during the packfile data
           stream, is made up of a leading 4-byte pkt-line length (typical of
           the pkt-line format), followed by a 1-byte stream code, followed by
           the actual data.
               The stream code can be one of:
                     1 - pack data
                     2 - progress messages
                     3 - fatal error message just before stream aborts
   server-option
       If advertised, indicates that any number of server specific options can
       be included in a request. This is done by sending each option as a
       "server-option=<option>" capability line in the capability-list section
       of a request.
       The provided options must not contain a NUL or LF character.
   object-format
       The server can advertise the object-format capability with a value X
       (in the form object-format=X) to notify the client that the server is
       able to deal with objects using hash algorithm X. If not specified, the
       server is assumed to only handle SHA-1. If the client would like to use
       a hash algorithm other than SHA-1, it should specify its object-format
       string.
   session-id=<session id>
       The server may advertise a session ID that can be used to identify this
       process across multiple requests. The client may advertise its own
       session ID back to the server as well.
       Session IDs should be unique to a given process. They must fit within a
       packet-line, and must not contain non-printable or whitespace
       characters. The current implementation uses trace2 session IDs (see
       api-trace2[1] for details), but this may change and users of the
       session ID should not rely on this fact.
   object-info
       object-info is the command to retrieve information about one or more
       objects. Its main purpose is to allow a client to make decisions based
       on this information without having to fully fetch objects. Object size
       is the only information that is currently supported.
       An object-info request takes the following arguments:
           size
           Requests size information to be returned for each listed object id.
           oid <oid>
           Indicates to the server an object which the client wants to obtain
           information for.
       The response of object-info is a list of the requested object ids and
       associated requested information, each separated by a single space.
           output = info flush-pkt
           info = PKT-LINE(attrs) LF)
                   *PKT-LINE(obj-info LF)
           attrs = attr | attrs SP attrs
           attr = "size"
           obj-info = obj-id SP obj-size
   bundle-uri
       If the bundle-uri capability is advertised, the server supports the
       `bundle-uri' command.
       The capability is currently advertised with no value (i.e. not
       "bundle-uri=somevalue"), a value may be added in the future for
       supporting command-wide extensions. Clients MUST ignore any unknown
       capability values and proceed with the 'bundle-uri` dialog they
       support.
       The bundle-uri command is intended to be issued before fetch to get
       URIs to bundle files (see git-bundle(1)) to "seed" and inform the
       subsequent fetch command.
       The client CAN issue bundle-uri before or after any other valid
       command. To be useful to clients it's expected that it'll be issued
       after an ls-refs and before fetch, but CAN be issued at any time in the
       dialog.
       DISCUSSION of bundle-uri
           The intent of the feature is optimize for server resource
           consumption in the common case by changing the common case of
           fetching a very large PACK during git-clone(1) into a smaller
           incremental fetch.
           It also allows servers to achieve better caching in combination
           with an uploadpack.packObjectsHook (see git-config(1)).
           By having new clones or fetches be a more predictable and common
           negotiation against the tips of recently produces *.bundle file(s).
           Servers might even pre-generate the results of such negotiations
           for the uploadpack.packObjectsHook as new pushes come in.
           One way that servers could take advantage of these bundles is that
           the server would anticipate that fresh clones will download a known
           bundle, followed by catching up to the current state of the
           repository using ref tips found in that bundle (or bundles).
       PROTOCOL for bundle-uri
           A bundle-uri request takes no arguments, and as noted above does
           not currently advertise a capability value. Both may be added in
           the future.
           When the client issues a command=bundle-uri request, the response
           is a list of key-value pairs provided as packet lines with value
           <key>=<value>. Each <key> should be interpreted as a config key
           from the bundle.* namespace to construct a list of bundles. These
           keys are grouped by a bundle.<id>. subsection, where each key
           corresponding to a given <id> contributes attributes to the bundle
           defined by that <id>. See git-config(1) for the specific details of
           these keys and how the Git client will interpret their values.
           Clients MUST parse the line according to the above format, lines
           that do not conform to the format SHOULD be discarded. The user MAY
           be warned in such a case.
       bundle-uri CLIENT AND SERVER EXPECTATIONS
           URI CONTENTS
               The content at the advertised URIs MUST be one of two types.
               The advertised URI may contain a bundle file that git bundle
               verify would accept. I.e. they MUST contain one or more
               reference tips for use by the client, MUST indicate
               prerequisites (in any) with standard "-" prefixes, and MUST
               indicate their "object-format", if applicable.
               The advertised URI may alternatively contain a plaintext file
               that git config --list would accept (with the --file option).
               The key-value pairs in this list are in the bundle.*  namespace
               (see git-config(1)).
           bundle-uri CLIENT ERROR RECOVERY
               A client MUST above all gracefully degrade on errors, whether
               that error is because of bad missing/data in the bundle URI(s),
               because that client is too dumb to e.g. understand and fully
               parse out bundle headers and their prerequisite relationships,
               or something else.
               Server operators should feel confident in turning on
               "bundle-uri" and not worry if e.g. their CDN goes down that
               clones or fetches will run into hard failures. Even if the
               server bundle(s) are incomplete, or bad in some way the client
               should still end up with a functioning repository, just as if
               it had chosen not to use this protocol extension.
               All subsequent discussion on client and server interaction MUST
               keep this in mind.
           bundle-uri SERVER TO CLIENT
               The ordering of the returned bundle uris is not significant.
               Clients MUST parse their headers to discover their contained
               OIDS and prerequisites. A client MUST consider the content of
               the bundle(s) themselves and their header as the ultimate
               source of truth.
               A server MAY even return bundle(s) that don't have any direct
               relationship to the repository being cloned (either through
               accident, or intentional "clever" configuration), and expect a
               client to sort out what data they'd like from the bundle(s), if
               any.
           bundle-uri CLIENT TO SERVER
               The client SHOULD provide reference tips found in the bundle
               header(s) as have lines in any subsequent fetch request. A
               client MAY also ignore the bundle(s) entirely if doing so is
               deemed worse for some reason, e.g. if the bundles can't be
               downloaded, it doesn't like the tips it finds etc.
           WHEN ADVERTISED BUNDLE(S) REQUIRE NO FURTHER NEGOTIATION
               If after issuing bundle-uri and ls-refs, and getting the
               header(s) of the bundle(s) the client finds that the ref tips
               it wants can be retrieved entirely from advertised bundle(s),
               the client MAY disconnect from the Git server. The results of
               such a clone or fetch should be indistinguishable from the
               state attained without using bundle-uri.
           EARLY CLIENT DISCONNECTIONS AND ERROR RECOVERY
               A client MAY perform an early disconnect while still
               downloading the bundle(s) (having streamed and parsed their
               headers). In such a case the client MUST gracefully recover
               from any errors related to finishing the download and
               validation of the bundle(s).
               I.e. a client might need to re-connect and issue a fetch
               command, and possibly fall back to not making use of bundle-uri
               at all.
               This "MAY" behavior is specified as such (and not a "SHOULD")
               on the assumption that a server advertising bundle uris is more
               likely than not to be serving up a relatively large repository,
               and to be pointing to URIs that have a good chance of being in
               working order. A client MAY e.g. look at the payload size of
               the bundles as a heuristic to see if an early disconnect is
               worth it, should falling back on a full "fetch" dialog be
               necessary.
           WHEN ADVERTISED BUNDLE(S) REQUIRE FURTHER NEGOTIATION
               A client SHOULD commence a negotiation of a PACK from the
               server via the "fetch" command using the OID tips found in
               advertised bundles, even if's still in the process of
               downloading those bundle(s).
               This allows for aggressive early disconnects from any
               interactive server dialog. The client blindly trusts that the
               advertised OID tips are relevant, and issues them as have
               lines, it then requests any tips it would like (usually from
               the "ls-refs" advertisement) via want lines. The server will
               then compute a (hopefully small) PACK with the expected
               difference between the tips from the bundle(s) and the data
               requested.
               The only connection the client then needs to keep active is to
               the concurrently downloading static bundle(s), when those and
               the incremental PACK are retrieved they should be inflated and
               validated. Any errors at this point should be gracefully
               recovered from, see above.
       bundle-uri PROTOCOL FEATURES
           The client constructs a bundle list from the <key>=<value> pairs
           provided by the server. These pairs are part of the bundle.*
           namespace as documented in git-config(1). In this section, we
           discuss some of these keys and describe the actions the client will
           do in response to this information.
           In particular, the bundle.version key specifies an integer value.
           The only accepted value at the moment is 1, but if the client sees
           an unexpected value here then the client MUST ignore the bundle
           list.
           As long as bundle.version is understood, all other unknown keys MAY
           be ignored by the client. The server will guarantee compatibility
           with older clients, though newer clients may be better able to use
           the extra keys to minimize downloads.
           Any backwards-incompatible addition of pre-URI key-value will be
           guarded by a new bundle.version value or values in bundle-uri
           capability advertisement itself, and/or by new future bundle-uri
           request arguments.
           Some example key-value pairs that are not currently implemented but
           could be implemented in the future include:
           o   Add a "hash=<val>" or "size=<bytes>" advertise the expected
               hash or size of the bundle file.
           o   Advertise that one or more bundle files are the same (to e.g.
               have clients round-robin or otherwise choose one of N possible
               files).
           o   A "oid=<OID>" shortcut and "prerequisite=<OID>" shortcut. For
               expressing the common case of a bundle with one tip and no
               prerequisites, or one tip and one prerequisite.
               This would allow for optimizing the common case of servers
               who'd like to provide one "big bundle" containing only their
               "main" branch, and/or incremental updates thereof.
               A client receiving such a a response MAY assume that they can
               skip retrieving the header from a bundle at the indicated URI,
               and thus save themselves and the server(s) the request(s)
               needed to inspect the headers of that bundle or bundles.
GIT
       Part of the git(1) suite
NOTES
        1. api-trace2
           file:///usr/share/doc/git/technical/api-trace2.html
Git 2.43.5                        05/31/2024                 GITPROTOCOL-V2(5)