gitprotocol-v2.html

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 441 <body class="manpage">
 442 <div id="header">
 443 <h1>gitprotocol-v2(5) Manual Page</h1>
 444 <h2 id="_name">NAME</h2>
 445 <div class="sectionbody">
 446 <p>gitprotocol-v2 - Git Wire Protocol, Version 2</p>
 447 </div>
 448 </div>
 449 <div id="content">
 450 <div class="sect1">
 451 <h2 id="_synopsis">SYNOPSIS</h2>
 452 <div class="sectionbody">
 453 <div class="verseblock">
 454 <pre class="content">&lt;over-the-wire-protocol&gt;</pre>
 455 </div>
 456 </div>
 457 </div>
 458 <div class="sect1">
 459 <h2 id="_description">DESCRIPTION</h2>
 460 <div class="sectionbody">
 461 <div class="paragraph">
 462 <p>This document presents a specification for a version 2 of Git&#8217;s wire
 463 protocol.  Protocol v2 will improve upon v1 in the following ways:</p>
 464 </div>
 465 <div class="ulist">
 466 <ul>
 467 <li>
 468 <p>Instead of multiple service names, multiple commands will be
 469 supported by a single service</p>
 470 </li>
 471 <li>
 472 <p>Easily extendable as capabilities are moved into their own section
 473 of the protocol, no longer being hidden behind a NUL byte and
 474 limited by the size of a pkt-line</p>
 475 </li>
 476 <li>
 477 <p>Separate out other information hidden behind NUL bytes (e.g. agent
 478 string as a capability and symrefs can be requested using <em>ls-refs</em>)</p>
 479 </li>
 480 <li>
 481 <p>Reference advertisement will be omitted unless explicitly requested</p>
 482 </li>
 483 <li>
 484 <p>ls-refs command to explicitly request some refs</p>
 485 </li>
 486 <li>
 487 <p>Designed with http and stateless-rpc in mind.  With clear flush
 488 semantics the http remote helper can simply act as a proxy</p>
 489 </li>
 490 </ul>
 491 </div>
 492 <div class="paragraph">
 493 <p>In protocol v2 communication is command oriented.  When first contacting a
 494 server a list of capabilities will be advertised.  Some of these capabilities
 495 will be commands which a client can request be executed.  Once a command
 496 has completed, a client can reuse the connection and request that other
 497 commands be executed.</p>
 498 </div>
 499 </div>
 500 </div>
 501 <div class="sect1">
 502 <h2 id="_packet_line_framing">Packet-Line Framing</h2>
 503 <div class="sectionbody">
 504 <div class="paragraph">
 505 <p>All communication is done using packet-line framing, just as in v1.  See
 506 <a href="gitprotocol-pack.html">gitprotocol-pack(5)</a> and <a href="gitprotocol-common.html">gitprotocol-common(5)</a> for more information.</p>
 507 </div>
 508 <div class="paragraph">
 509 <p>In protocol v2 these special packets will have the following semantics:</p>
 510 </div>
 511 <div class="ulist">
 512 <ul>
 513 <li>
 514 <p><em>0000</em> Flush Packet (flush-pkt) - indicates the end of a message</p>
 515 </li>
 516 <li>
 517 <p><em>0001</em> Delimiter Packet (delim-pkt) - separates sections of a message</p>
 518 </li>
 519 <li>
 520 <p><em>0002</em> Response End Packet (response-end-pkt) - indicates the end of a
 521 response for stateless connections</p>
 522 </li>
 523 </ul>
 524 </div>
 525 </div>
 526 </div>
 527 <div class="sect1">
 528 <h2 id="_initial_client_request">Initial Client Request</h2>
 529 <div class="sectionbody">
 530 <div class="paragraph">
 531 <p>In general a client can request to speak protocol v2 by sending
 532 <code>version=2</code> through the respective side-channel for the transport being
 533 used which inevitably sets <code>GIT_PROTOCOL</code>.  More information can be
 534 found in <a href="gitprotocol-pack.html">gitprotocol-pack(5)</a> and <a href="gitprotocol-http.html">gitprotocol-http(5)</a>, as well as the
 535 <code>GIT_PROTOCOL</code> definition in <code>git.txt</code>. In all cases the
 536 response from the server is the capability advertisement.</p>
 537 </div>
 538 <div class="sect2">
 539 <h3 id="_git_transport">Git Transport</h3>
 540 <div class="paragraph">
 541 <p>When using the git:// transport, you can request to use protocol v2 by
 542 sending "version=2" as an extra parameter:</p>
 543 </div>
 544 <div class="literalblock">
 545 <div class="content">
 546 <pre>003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0</pre>
 547 </div>
 548 </div>
 549 </div>
 550 <div class="sect2">
 551 <h3 id="_ssh_and_file_transport">SSH and File Transport</h3>
 552 <div class="paragraph">
 553 <p>When using either the ssh:// or file:// transport, the GIT_PROTOCOL
 554 environment variable must be set explicitly to include "version=2".
 555 The server may need to be configured to allow this environment variable
 556 to pass.</p>
 557 </div>
 558 </div>
 559 <div class="sect2">
 560 <h3 id="_http_transport">HTTP Transport</h3>
 561 <div class="paragraph">
 562 <p>When using the http:// or https:// transport a client makes a "smart"
 563 info/refs request as described in <a href="gitprotocol-http.html">gitprotocol-http(5)</a> and requests that
 564 v2 be used by supplying "version=2" in the <code>Git-Protocol</code> header.</p>
 565 </div>
 566 <div class="literalblock">
 567 <div class="content">
 568 <pre>C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0
 569 C: Git-Protocol: version=2</pre>
 570 </div>
 571 </div>
 572 <div class="paragraph">
 573 <p>A v2 server would reply:</p>
 574 </div>
 575 <div class="literalblock">
 576 <div class="content">
 577 <pre>S: 200 OK
 578 S: &lt;Some headers&gt;
 579 S: ...
 580 S:
 581 S: 000eversion 2\n
 582 S: &lt;capability-advertisement&gt;</pre>
 583 </div>
 584 </div>
 585 <div class="paragraph">
 586 <p>Subsequent requests are then made directly to the service
 587 <code>$GIT_URL/git-upload-pack</code>. (This works the same for git-receive-pack).</p>
 588 </div>
 589 <div class="paragraph">
 590 <p>Uses the <code>--http-backend-info-refs</code> option to
 591 <a href="git-upload-pack.html">git-upload-pack(1)</a>.</p>
 592 </div>
 593 <div class="paragraph">
 594 <p>The server may need to be configured to pass this header&#8217;s contents via
 595 the <code>GIT_PROTOCOL</code> variable. See the discussion in <code>git-http-backend.txt</code>.</p>
 596 </div>
 597 </div>
 598 </div>
 599 </div>
 600 <div class="sect1">
 601 <h2 id="_capability_advertisement">Capability Advertisement</h2>
 602 <div class="sectionbody">
 603 <div class="paragraph">
 604 <p>A server which decides to communicate (based on a request from a client)
 605 using protocol version 2, notifies the client by sending a version string
 606 in its initial response followed by an advertisement of its capabilities.
 607 Each capability is a key with an optional value.  Clients must ignore all
 608 unknown keys.  Semantics of unknown values are left to the definition of
 609 each key.  Some capabilities will describe commands which can be requested
 610 to be executed by the client.</p>
 611 </div>
 612 <div class="literalblock">
 613 <div class="content">
 614 <pre>capability-advertisement = protocol-version
 615       capability-list
 616       flush-pkt</pre>
 617 </div>
 618 </div>
 619 <div class="literalblock">
 620 <div class="content">
 621 <pre>protocol-version = PKT-LINE("version 2" LF)
 622 capability-list = *capability
 623 capability = PKT-LINE(key[=value] LF)</pre>
 624 </div>
 625 </div>
 626 <div class="literalblock">
 627 <div class="content">
 628 <pre>key = 1*(ALPHA | DIGIT | "-_")
 629 value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()&lt;&gt;!@#$%^&amp;*+=:;")</pre>
 630 </div>
 631 </div>
 632 </div>
 633 </div>
 634 <div class="sect1">
 635 <h2 id="_command_request">Command Request</h2>
 636 <div class="sectionbody">
 637 <div class="paragraph">
 638 <p>After receiving the capability advertisement, a client can then issue a
 639 request to select the command it wants with any particular capabilities
 640 or arguments.  There is then an optional section where the client can
 641 provide any command specific parameters or queries.  Only a single
 642 command can be requested at a time.</p>
 643 </div>
 644 <div class="literalblock">
 645 <div class="content">
 646 <pre>request = empty-request | command-request
 647 empty-request = flush-pkt
 648 command-request = command
 649     capability-list
 650     delim-pkt
 651     command-args
 652     flush-pkt
 653 command = PKT-LINE("command=" key LF)
 654 command-args = *command-specific-arg</pre>
 655 </div>
 656 </div>
 657 <div class="literalblock">
 658 <div class="content">
 659 <pre>command-specific-args are packet line framed arguments defined by
 660 each individual command.</pre>
 661 </div>
 662 </div>
 663 <div class="paragraph">
 664 <p>The server will then check to ensure that the client&#8217;s request is
 665 comprised of a valid command as well as valid capabilities which were
 666 advertised.  If the request is valid the server will then execute the
 667 command.  A server MUST wait till it has received the client&#8217;s entire
 668 request before issuing a response.  The format of the response is
 669 determined by the command being executed, but in all cases a flush-pkt
 670 indicates the end of the response.</p>
 671 </div>
 672 <div class="paragraph">
 673 <p>When a command has finished, and the client has received the entire
 674 response from the server, a client can either request that another
 675 command be executed or can terminate the connection.  A client may
 676 optionally send an empty request consisting of just a flush-pkt to
 677 indicate that no more requests will be made.</p>
 678 </div>
 679 </div>
 680 </div>
 681 <div class="sect1">
 682 <h2 id="_capabilities">Capabilities</h2>
 683 <div class="sectionbody">
 684 <div class="paragraph">
 685 <p>There are two different types of capabilities: normal capabilities,
 686 which can be used to convey information or alter the behavior of a
 687 request, and commands, which are the core actions that a client wants to
 688 perform (fetch, push, etc).</p>
 689 </div>
 690 <div class="paragraph">
 691 <p>Protocol version 2 is stateless by default.  This means that all commands
 692 must only last a single round and be stateless from the perspective of the
 693 server side, unless the client has requested a capability indicating that
 694 state should be maintained by the server.  Clients MUST NOT require state
 695 management on the server side in order to function correctly.  This
 696 permits simple round-robin load-balancing on the server side, without
 697 needing to worry about state management.</p>
 698 </div>
 699 <div class="sect2">
 700 <h3 id="_agent">agent</h3>
 701 <div class="paragraph">
 702 <p>The server can advertise the <code>agent</code> capability with a value <code>X</code> (in the
 703 form <code>agent=X</code>) to notify the client that the server is running version
 704 <code>X</code>.  The client may optionally send its own agent string by including
 705 the <code>agent</code> capability with a value <code>Y</code> (in the form <code>agent=Y</code>) in its
 706 request to the server (but it MUST NOT do so if the server did not
 707 advertise the agent capability). The <code>X</code> and <code>Y</code> strings may contain any
 708 printable ASCII characters except space (i.e., the byte range 32 &lt; x &lt;
 709 127), and are typically of the form "package/version" (e.g.,
 710 "git/1.8.3.1"). The agent strings are purely informative for statistics
 711 and debugging purposes, and MUST NOT be used to programmatically assume
 712 the presence or absence of particular features.</p>
 713 </div>
 714 </div>
 715 <div class="sect2">
 716 <h3 id="_ls_refs">ls-refs</h3>
 717 <div class="paragraph">
 718 <p><code>ls-refs</code> is the command used to request a reference advertisement in v2.
 719 Unlike the current reference advertisement, ls-refs takes in arguments
 720 which can be used to limit the refs sent from the server.</p>
 721 </div>
 722 <div class="paragraph">
 723 <p>Additional features not supported in the base command will be advertised
 724 as the value of the command in the capability advertisement in the form
 725 of a space separated list of features: "&lt;command&gt;=&lt;feature-1&gt; &lt;feature-2&gt;"</p>
 726 </div>
 727 <div class="paragraph">
 728 <p>ls-refs takes in the following arguments:</p>
 729 </div>
 730 <div class="literalblock">
 731 <div class="content">
 732 <pre>   symrefs
 733 In addition to the object pointed by it, show the underlying ref
 734 pointed by it when showing a symbolic ref.
 735    peel
 736 Show peeled tags.
 737    ref-prefix &lt;prefix&gt;
 738 When specified, only references having a prefix matching one of
 739 the provided prefixes are displayed. Multiple instances may be
 740 given, in which case references matching any prefix will be
 741 shown. Note that this is purely for optimization; a server MAY
 742 show refs not matching the prefix if it chooses, and clients
 743 should filter the result themselves.</pre>
 744 </div>
 745 </div>
 746 <div class="paragraph">
 747 <p>If the <em>unborn</em> feature is advertised the following argument can be
 748 included in the client&#8217;s request.</p>
 749 </div>
 750 <div class="literalblock">
 751 <div class="content">
 752 <pre>   unborn
 753 The server will send information about HEAD even if it is a symref
 754 pointing to an unborn branch in the form "unborn HEAD
 755 symref-target:&lt;target&gt;".</pre>
 756 </div>
 757 </div>
 758 <div class="paragraph">
 759 <p>The output of ls-refs is as follows:</p>
 760 </div>
 761 <div class="literalblock">
 762 <div class="content">
 763 <pre>output = *ref
 764   flush-pkt
 765 obj-id-or-unborn = (obj-id | "unborn")
 766 ref = PKT-LINE(obj-id-or-unborn SP refname *(SP ref-attribute) LF)
 767 ref-attribute = (symref | peeled)
 768 symref = "symref-target:" symref-target
 769 peeled = "peeled:" obj-id</pre>
 770 </div>
 771 </div>
 772 </div>
 773 <div class="sect2">
 774 <h3 id="_fetch">fetch</h3>
 775 <div class="paragraph">
 776 <p><code>fetch</code> is the command used to fetch a packfile in v2.  It can be looked
 777 at as a modified version of the v1 fetch where the ref-advertisement is
 778 stripped out (since the <code>ls-refs</code> command fills that role) and the
 779 message format is tweaked to eliminate redundancies and permit easy
 780 addition of future extensions.</p>
 781 </div>
 782 <div class="paragraph">
 783 <p>Additional features not supported in the base command will be advertised
 784 as the value of the command in the capability advertisement in the form
 785 of a space separated list of features: "&lt;command&gt;=&lt;feature-1&gt; &lt;feature-2&gt;"</p>
 786 </div>
 787 <div class="paragraph">
 788 <p>A <code>fetch</code> request can take the following arguments:</p>
 789 </div>
 790 <div class="literalblock">
 791 <div class="content">
 792 <pre>   want &lt;oid&gt;
 793 Indicates to the server an object which the client wants to
 794 retrieve.  Wants can be anything and are not limited to
 795 advertised objects.</pre>
 796 </div>
 797 </div>
 798 <div class="literalblock">
 799 <div class="content">
 800 <pre>   have &lt;oid&gt;
 801 Indicates to the server an object which the client has locally.
 802 This allows the server to make a packfile which only contains
 803 the objects that the client needs. Multiple 'have' lines can be
 804 supplied.</pre>
 805 </div>
 806 </div>
 807 <div class="literalblock">
 808 <div class="content">
 809 <pre>   done
 810 Indicates to the server that negotiation should terminate (or
 811 not even begin if performing a clone) and that the server should
 812 use the information supplied in the request to construct the
 813 packfile.</pre>
 814 </div>
 815 </div>
 816 <div class="literalblock">
 817 <div class="content">
 818 <pre>   thin-pack
 819 Request that a thin pack be sent, which is a pack with deltas
 820 which reference base objects not contained within the pack (but
 821 are known to exist at the receiving end). This can reduce the
 822 network traffic significantly, but it requires the receiving end
 823 to know how to "thicken" these packs by adding the missing bases
 824 to the pack.</pre>
 825 </div>
 826 </div>
 827 <div class="literalblock">
 828 <div class="content">
 829 <pre>   no-progress
 830 Request that progress information that would normally be sent on
 831 side-band channel 2, during the packfile transfer, should not be
 832 sent.  However, the side-band channel 3 is still used for error
 833 responses.</pre>
 834 </div>
 835 </div>
 836 <div class="literalblock">
 837 <div class="content">
 838 <pre>   include-tag
 839 Request that annotated tags should be sent if the objects they
 840 point to are being sent.</pre>
 841 </div>
 842 </div>
 843 <div class="literalblock">
 844 <div class="content">
 845 <pre>   ofs-delta
 846 Indicate that the client understands PACKv2 with delta referring
 847 to its base by position in pack rather than by an oid.  That is,
 848 they can read OBJ_OFS_DELTA (aka type 6) in a packfile.</pre>
 849 </div>
 850 </div>
 851 <div class="paragraph">
 852 <p>If the <em>shallow</em> feature is advertised the following arguments can be
 853 included in the clients request as well as the potential addition of the
 854 <em>shallow-info</em> section in the server&#8217;s response as explained below.</p>
 855 </div>
 856 <div class="literalblock">
 857 <div class="content">
 858 <pre>   shallow &lt;oid&gt;
 859 A client must notify the server of all commits for which it only
 860 has shallow copies (meaning that it doesn't have the parents of
 861 a commit) by supplying a 'shallow &lt;oid&gt;' line for each such
 862 object so that the server is aware of the limitations of the
 863 client's history.  This is so that the server is aware that the
 864 client may not have all objects reachable from such commits.</pre>
 865 </div>
 866 </div>
 867 <div class="literalblock">
 868 <div class="content">
 869 <pre>   deepen &lt;depth&gt;
 870 Requests that the fetch/clone should be shallow having a commit
 871 depth of &lt;depth&gt; relative to the remote side.</pre>
 872 </div>
 873 </div>
 874 <div class="literalblock">
 875 <div class="content">
 876 <pre>   deepen-relative
 877 Requests that the semantics of the "deepen" command be changed
 878 to indicate that the depth requested is relative to the client's
 879 current shallow boundary, instead of relative to the requested
 880 commits.</pre>
 881 </div>
 882 </div>
 883 <div class="literalblock">
 884 <div class="content">
 885 <pre>   deepen-since &lt;timestamp&gt;
 886 Requests that the shallow clone/fetch should be cut at a
 887 specific time, instead of depth.  Internally it's equivalent to
 888 doing "git rev-list --max-age=&lt;timestamp&gt;". Cannot be used with
 889 "deepen".</pre>
 890 </div>
 891 </div>
 892 <div class="literalblock">
 893 <div class="content">
 894 <pre>   deepen-not &lt;rev&gt;
 895 Requests that the shallow clone/fetch should be cut at a
 896 specific revision specified by '&lt;rev&gt;', instead of a depth.
 897 Internally it's equivalent of doing "git rev-list --not &lt;rev&gt;".
 898 Cannot be used with "deepen", but can be used with
 899 "deepen-since".</pre>
 900 </div>
 901 </div>
 902 <div class="paragraph">
 903 <p>If the <em>filter</em> feature is advertised, the following argument can be
 904 included in the client&#8217;s request:</p>
 905 </div>
 906 <div class="literalblock">
 907 <div class="content">
 908 <pre>   filter &lt;filter-spec&gt;
 909 Request that various objects from the packfile be omitted
 910 using one of several filtering techniques. These are intended
 911 for use with partial clone and partial fetch operations. See
 912 `rev-list` for possible "filter-spec" values. When communicating
 913 with other processes, senders SHOULD translate scaled integers
 914 (e.g. "1k") into a fully-expanded form (e.g. "1024") to aid
 915 interoperability with older receivers that may not understand
 916 newly-invented scaling suffixes. However, receivers SHOULD
 917 accept the following suffixes: 'k', 'm', and 'g' for 1024,
 918 1048576, and 1073741824, respectively.</pre>
 919 </div>
 920 </div>
 921 <div class="paragraph">
 922 <p>If the <em>ref-in-want</em> feature is advertised, the following argument can
 923 be included in the client&#8217;s request as well as the potential addition of
 924 the <em>wanted-refs</em> section in the server&#8217;s response as explained below.</p>
 925 </div>
 926 <div class="literalblock">
 927 <div class="content">
 928 <pre>   want-ref &lt;ref&gt;
 929 Indicates to the server that the client wants to retrieve a
 930 particular ref, where &lt;ref&gt; is the full name of a ref on the
 931 server.  It is a protocol error to send want-ref for the
 932 same ref more than once.</pre>
 933 </div>
 934 </div>
 935 <div class="paragraph">
 936 <p>If the <em>sideband-all</em> feature is advertised, the following argument can be
 937 included in the client&#8217;s request:</p>
 938 </div>
 939 <div class="literalblock">
 940 <div class="content">
 941 <pre>   sideband-all
 942 Instruct the server to send the whole response multiplexed, not just
 943 the packfile section. All non-flush and non-delim PKT-LINE in the
 944 response (not only in the packfile section) will then start with a byte
 945 indicating its sideband (1, 2, or 3), and the server may send "0005\2"
 946 (a PKT-LINE of sideband 2 with no payload) as a keepalive packet.</pre>
 947 </div>
 948 </div>
 949 <div class="paragraph">
 950 <p>If the <em>packfile-uris</em> feature is advertised, the following argument
 951 can be included in the client&#8217;s request as well as the potential
 952 addition of the <em>packfile-uris</em> section in the server&#8217;s response as
 953 explained below. Note that at most one <code>packfile-uris</code> line can be sent
 954 to the server.</p>
 955 </div>
 956 <div class="literalblock">
 957 <div class="content">
 958 <pre>   packfile-uris &lt;comma-separated-list-of-protocols&gt;
 959 Indicates to the server that the client is willing to receive
 960 URIs of any of the given protocols in place of objects in the
 961 sent packfile. Before performing the connectivity check, the
 962 client should download from all given URIs. Currently, the
 963 protocols supported are "http" and "https".</pre>
 964 </div>
 965 </div>
 966 <div class="paragraph">
 967 <p>If the <em>wait-for-done</em> feature is advertised, the following argument
 968 can be included in the client&#8217;s request.</p>
 969 </div>
 970 <div class="literalblock">
 971 <div class="content">
 972 <pre>   wait-for-done
 973 Indicates to the server that it should never send "ready", but
 974 should wait for the client to say "done" before sending the
 975 packfile.</pre>
 976 </div>
 977 </div>
 978 <div class="paragraph">
 979 <p>The response of <code>fetch</code> is broken into a number of sections separated by
 980 delimiter packets (0001), with each section beginning with its section
 981 header. Most sections are sent only when the packfile is sent.</p>
 982 </div>
 983 <div class="literalblock">
 984 <div class="content">
 985 <pre>output = acknowledgements flush-pkt |
 986   [acknowledgments delim-pkt] [shallow-info delim-pkt]
 987   [wanted-refs delim-pkt] [packfile-uris delim-pkt]
 988   packfile flush-pkt</pre>
 989 </div>
 990 </div>
 991 <div class="literalblock">
 992 <div class="content">
 993 <pre>acknowledgments = PKT-LINE("acknowledgments" LF)
 994     (nak | *ack)
 995     (ready)
 996 ready = PKT-LINE("ready" LF)
 997 nak = PKT-LINE("NAK" LF)
 998 ack = PKT-LINE("ACK" SP obj-id LF)</pre>
 999 </div>
1000 </div>
1001 <div class="literalblock">
1002 <div class="content">
1003 <pre>shallow-info = PKT-LINE("shallow-info" LF)
1004  *PKT-LINE((shallow | unshallow) LF)
1005 shallow = "shallow" SP obj-id
1006 unshallow = "unshallow" SP obj-id</pre>
1007 </div>
1008 </div>
1009 <div class="literalblock">
1010 <div class="content">
1011 <pre>wanted-refs = PKT-LINE("wanted-refs" LF)
1012 *PKT-LINE(wanted-ref LF)
1013 wanted-ref = obj-id SP refname</pre>
1014 </div>
1015 </div>
1016 <div class="literalblock">
1017 <div class="content">
1018 <pre>packfile-uris = PKT-LINE("packfile-uris" LF) *packfile-uri
1019 packfile-uri = PKT-LINE(40*(HEXDIGIT) SP *%x20-ff LF)</pre>
1020 </div>
1021 </div>
1022 <div class="literalblock">
1023 <div class="content">
1024 <pre>packfile = PKT-LINE("packfile" LF)
1025     *PKT-LINE(%x01-03 *%x00-ff)</pre>
1026 </div>
1027 </div>
1028 <div class="literalblock">
1029 <div class="content">
1030 <pre>   acknowledgments section
1031 * If the client determines that it is finished with negotiations by
1032   sending a "done" line (thus requiring the server to send a packfile),
1033   the acknowledgments sections MUST be omitted from the server's
1034   response.</pre>
1035 </div>
1036 </div>
1037 <div class="ulist">
1038 <ul>
1039 <li>
1040 <p>Always begins with the section header "acknowledgments"</p>
1041 </li>
1042 <li>
1043 <p>The server will respond with "NAK" if none of the object ids sent
1044 as have lines were common.</p>
1045 </li>
1046 <li>
1047 <p>The server will respond with "ACK obj-id" for all of the
1048 object ids sent as have lines which are common.</p>
1049 </li>
1050 <li>
1051 <p>A response cannot have both "ACK" lines as well as a "NAK"
1052 line.</p>
1053 </li>
1054 <li>
1055 <p>The server will respond with a "ready" line indicating that
1056 the server has found an acceptable common base and is ready to
1057 make and send a packfile (which will be found in the packfile
1058 section of the same response)</p>
1059 </li>
1060 <li>
1061 <p>If the server has found a suitable cut point and has decided
1062 to send a "ready" line, then the server can decide to (as an
1063 optimization) omit any "ACK" lines it would have sent during
1064 its response.  This is because the server will have already
1065 determined the objects it plans to send to the client and no
1066 further negotiation is needed.</p>
1067 <div class="literalblock">
1068 <div class="content">
1069 <pre>   shallow-info section
1070 * If the client has requested a shallow fetch/clone, a shallow
1071   client requests a fetch or the server is shallow then the
1072   server's response may include a shallow-info section.  The
1073   shallow-info section will be included if (due to one of the
1074   above conditions) the server needs to inform the client of any
1075   shallow boundaries or adjustments to the clients already
1076   existing shallow boundaries.</pre>
1077 </div>
1078 </div>
1079 </li>
1080 <li>
1081 <p>Always begins with the section header "shallow-info"</p>
1082 </li>
1083 <li>
1084 <p>If a positive depth is requested, the server will compute the
1085 set of commits which are no deeper than the desired depth.</p>
1086 </li>
1087 <li>
1088 <p>The server sends a "shallow obj-id" line for each commit whose
1089 parents will not be sent in the following packfile.</p>
1090 </li>
1091 <li>
1092 <p>The server sends an "unshallow obj-id" line for each commit
1093 which the client has indicated is shallow, but is no longer
1094 shallow as a result of the fetch (due to its parents being
1095 sent in the following packfile).</p>
1096 </li>
1097 <li>
1098 <p>The server MUST NOT send any "unshallow" lines for anything
1099 which the client has not indicated was shallow as a part of
1100 its request.</p>
1101 <div class="literalblock">
1102 <div class="content">
1103 <pre>   wanted-refs section
1104 * This section is only included if the client has requested a
1105   ref using a 'want-ref' line and if a packfile section is also
1106   included in the response.</pre>
1107 </div>
1108 </div>
1109 </li>
1110 <li>
1111 <p>Always begins with the section header "wanted-refs".</p>
1112 </li>
1113 <li>
1114 <p>The server will send a ref listing ("&lt;oid&gt; &lt;refname&gt;") for
1115 each reference requested using <em>want-ref</em> lines.</p>
1116 </li>
1117 <li>
1118 <p>The server MUST NOT send any refs which were not requested
1119 using <em>want-ref</em> lines.</p>
1120 <div class="literalblock">
1121 <div class="content">
1122 <pre>   packfile-uris section
1123 * This section is only included if the client sent
1124   'packfile-uris' and the server has at least one such URI to
1125   send.</pre>
1126 </div>
1127 </div>
1128 </li>
1129 <li>
1130 <p>Always begins with the section header "packfile-uris".</p>
1131 </li>
1132 <li>
1133 <p>For each URI the server sends, it sends a hash of the pack&#8217;s
1134 contents (as output by git index-pack) followed by the URI.</p>
1135 </li>
1136 <li>
1137 <p>The hashes are 40 hex characters long. When Git upgrades to a new
1138 hash algorithm, this might need to be updated. (It should match
1139 whatever index-pack outputs after "pack\t" or "keep\t".</p>
1140 <div class="literalblock">
1141 <div class="content">
1142 <pre>   packfile section
1143 * This section is only included if the client has sent 'want'
1144   lines in its request and either requested that no more
1145   negotiation be done by sending 'done' or if the server has
1146   decided it has found a sufficient cut point to produce a
1147   packfile.</pre>
1148 </div>
1149 </div>
1150 </li>
1151 <li>
1152 <p>Always begins with the section header "packfile"</p>
1153 </li>
1154 <li>
1155 <p>The transmission of the packfile begins immediately after the
1156 section header</p>
1157 </li>
1158 <li>
1159 <p>The data transfer of the packfile is always multiplexed, using
1160 the same semantics of the <em>side-band-64k</em> capability from
1161 protocol version 1.  This means that each packet, during the
1162 packfile data stream, is made up of a leading 4-byte pkt-line
1163 length (typical of the pkt-line format), followed by a 1-byte
1164 stream code, followed by the actual data.</p>
1165 <div class="literalblock">
1166 <div class="content">
1167 <pre> The stream code can be one of:
1168 1 - pack data
1169 2 - progress messages
1170 3 - fatal error message just before stream aborts</pre>
1171 </div>
1172 </div>
1173 </li>
1174 </ul>
1175 </div>
1176 </div>
1177 <div class="sect2">
1178 <h3 id="_server_option">server-option</h3>
1179 <div class="paragraph">
1180 <p>If advertised, indicates that any number of server specific options can be
1181 included in a request.  This is done by sending each option as a
1182 "server-option=&lt;option&gt;" capability line in the capability-list section of
1183 a request.</p>
1184 </div>
1185 <div class="paragraph">
1186 <p>The provided options must not contain a NUL or LF character.</p>
1187 </div>
1188 </div>
1189 <div class="sect2">
1190 <h3 id="_object_format">object-format</h3>
1191 <div class="paragraph">
1192 <p>The server can advertise the <code>object-format</code> capability with a value <code>X</code> (in the
1193 form <code>object-format=X</code>) to notify the client that the server is able to deal
1194 with objects using hash algorithm X.  If not specified, the server is assumed to
1195 only handle SHA-1.  If the client would like to use a hash algorithm other than
1196 SHA-1, it should specify its object-format string.</p>
1197 </div>
1198 </div>
1199 <div class="sect2">
1200 <h3 id="_session_idsession_id">session-id=&lt;session-id&gt;</h3>
1201 <div class="paragraph">
1202 <p>The server may advertise a session ID that can be used to identify this process
1203 across multiple requests. The client may advertise its own session ID back to
1204 the server as well.</p>
1205 </div>
1206 <div class="paragraph">
1207 <p>Session IDs should be unique to a given process. They must fit within a
1208 packet-line, and must not contain non-printable or whitespace characters. The
1209 current implementation uses trace2 session IDs (see
1210 <a href="technical/api-trace2.html">api-trace2</a> for details), but this may change
1211 and users of the session ID should not rely on this fact.</p>
1212 </div>
1213 </div>
1214 <div class="sect2">
1215 <h3 id="_object_info">object-info</h3>
1216 <div class="paragraph">
1217 <p><code>object-info</code> is the command to retrieve information about one or more objects.
1218 Its main purpose is to allow a client to make decisions based on this
1219 information without having to fully fetch objects. Object size is the only
1220 information that is currently supported.</p>
1221 </div>
1222 <div class="paragraph">
1223 <p>An <code>object-info</code> request takes the following arguments:</p>
1224 </div>
1225 <div class="literalblock">
1226 <div class="content">
1227 <pre>size
1228 Requests size information to be returned for each listed object id.</pre>
1229 </div>
1230 </div>
1231 <div class="literalblock">
1232 <div class="content">
1233 <pre>oid &lt;oid&gt;
1234 Indicates to the server an object which the client wants to obtain
1235 information for.</pre>
1236 </div>
1237 </div>
1238 <div class="paragraph">
1239 <p>The response of <code>object-info</code> is a list of the requested object ids
1240 and associated requested information, each separated by a single space.</p>
1241 </div>
1242 <div class="literalblock">
1243 <div class="content">
1244 <pre>output = info flush-pkt</pre>
1245 </div>
1246 </div>
1247 <div class="literalblock">
1248 <div class="content">
1249 <pre>info = PKT-LINE(attrs) LF)
1250         *PKT-LINE(obj-info LF)</pre>
1251 </div>
1252 </div>
1253 <div class="literalblock">
1254 <div class="content">
1255 <pre>attrs = attr | attrs SP attrs</pre>
1256 </div>
1257 </div>
1258 <div class="literalblock">
1259 <div class="content">
1260 <pre>attr = "size"</pre>
1261 </div>
1262 </div>
1263 <div class="literalblock">
1264 <div class="content">
1265 <pre>obj-info = obj-id SP obj-size</pre>
1266 </div>
1267 </div>
1268 </div>
1269 <div class="sect2">
1270 <h3 id="_bundle_uri">bundle-uri</h3>
1271 <div class="paragraph">
1272 <p>If the <em>bundle-uri</em> capability is advertised, the server supports the
1273 &#8216;bundle-uri&#8217; command.</p>
1274 </div>
1275 <div class="paragraph">
1276 <p>The capability is currently advertised with no value (i.e. not
1277 "bundle-uri=somevalue"), a value may be added in the future for
1278 supporting command-wide extensions. Clients MUST ignore any unknown
1279 capability values and proceed with the 'bundle-uri` dialog they
1280 support.</p>
1281 </div>
1282 <div class="paragraph">
1283 <p>The <em>bundle-uri</em> command is intended to be issued before <code>fetch</code> to
1284 get URIs to bundle files (see <a href="git-bundle.html">git-bundle(1)</a>) to "seed" and
1285 inform the subsequent <code>fetch</code> command.</p>
1286 </div>
1287 <div class="paragraph">
1288 <p>The client CAN issue <code>bundle-uri</code> before or after any other valid
1289 command. To be useful to clients it&#8217;s expected that it&#8217;ll be issued
1290 after an <code>ls-refs</code> and before <code>fetch</code>, but CAN be issued at any time
1291 in the dialog.</p>
1292 </div>
1293 <div class="sect3">
1294 <h4 id="_discussion_of_bundle_uri">DISCUSSION of bundle-uri</h4>
1295 <div class="paragraph">
1296 <p>The intent of the feature is optimize for server resource consumption
1297 in the common case by changing the common case of fetching a very
1298 large PACK during <a href="git-clone.html">git-clone(1)</a> into a smaller incremental
1299 fetch.</p>
1300 </div>
1301 <div class="paragraph">
1302 <p>It also allows servers to achieve better caching in combination with
1303 an <code>uploadpack.packObjectsHook</code> (see <a href="git-config.html">git-config(1)</a>).</p>
1304 </div>
1305 <div class="paragraph">
1306 <p>By having new clones or fetches be a more predictable and common
1307 negotiation against the tips of recently produces *.bundle file(s).
1308 Servers might even pre-generate the results of such negotiations for
1309 the <code>uploadpack.packObjectsHook</code> as new pushes come in.</p>
1310 </div>
1311 <div class="paragraph">
1312 <p>One way that servers could take advantage of these bundles is that the
1313 server would anticipate that fresh clones will download a known bundle,
1314 followed by catching up to the current state of the repository using ref
1315 tips found in that bundle (or bundles).</p>
1316 </div>
1317 </div>
1318 <div class="sect3">
1319 <h4 id="_protocol_for_bundle_uri">PROTOCOL for bundle-uri</h4>
1320 <div class="paragraph">
1321 <p>A <code>bundle-uri</code> request takes no arguments, and as noted above does not
1322 currently advertise a capability value. Both may be added in the
1323 future.</p>
1324 </div>
1325 <div class="paragraph">
1326 <p>When the client issues a <code>command=bundle-uri</code> request, the response is a
1327 list of key-value pairs provided as packet lines with value
1328 <em>&lt;key&gt;</em><code>=</code><em>&lt;value&gt;</em>. Each <em>&lt;key&gt;</em> should be interpreted as a config key from
1329 the <code>bundle.</code>* namespace to construct a list of bundles. These keys are
1330 grouped by a <code>bundle.</code><em>&lt;id&gt;</em>. subsection, where each key corresponding to a
1331 given <em>&lt;id&gt;</em> contributes attributes to the bundle defined by that <em>&lt;id&gt;</em>.
1332 See <a href="git-config.html">git-config(1)</a> for the specific details of these keys and how
1333 the Git client will interpret their values.</p>
1334 </div>
1335 <div class="paragraph">
1336 <p>Clients MUST parse the line according to the above format, lines that do
1337 not conform to the format SHOULD be discarded. The user MAY be warned in
1338 such a case.</p>
1339 </div>
1340 </div>
1341 <div class="sect3">
1342 <h4 id="_bundle_uri_client_and_server_expectations">bundle-uri CLIENT AND SERVER EXPECTATIONS</h4>
1343 <div class="dlist">
1344 <dl>
1345 <dt class="hdlist1">URI CONTENTS</dt>
1346 <dd>
1347 <p>The content at the advertised URIs MUST be one of two types.</p>
1348 <div class="paragraph">
1349 <p>The advertised URI may contain a bundle file that <code>git</code> <code>bundle</code> <code>verify</code>
1350 would accept. I.e. they MUST contain one or more reference tips for
1351 use by the client, MUST indicate prerequisites (in any) with standard
1352 "-" prefixes, and MUST indicate their "object-format", if
1353 applicable.</p>
1354 </div>
1355 <div class="paragraph">
1356 <p>The advertised URI may alternatively contain a plaintext file that <code>git</code>
1357 <code>config</code> <code>--list</code> would accept (with the <code>--file</code> option). The key-value
1358 pairs in this list are in the <code>bundle.</code>* namespace (see
1359 <a href="git-config.html">git-config(1)</a>).</p>
1360 </div>
1361 </dd>
1362 <dt class="hdlist1">bundle-uri CLIENT ERROR RECOVERY</dt>
1363 <dd>
1364 <p>A client MUST above all gracefully degrade on errors, whether that
1365 error is because of bad missing/data in the bundle URI(s), because
1366 that client is too dumb to e.g. understand and fully parse out bundle
1367 headers and their prerequisite relationships, or something else.</p>
1368 <div class="paragraph">
1369 <p>Server operators should feel confident in turning on "bundle-uri" and
1370 not worry if e.g. their CDN goes down that clones or fetches will run
1371 into hard failures. Even if the server bundle(s) are
1372 incomplete, or bad in some way the client should still end up with a
1373 functioning repository, just as if it had chosen not to use this
1374 protocol extension.</p>
1375 </div>
1376 <div class="paragraph">
1377 <p>All subsequent discussion on client and server interaction MUST keep
1378 this in mind.</p>
1379 </div>
1380 </dd>
1381 <dt class="hdlist1">bundle-uri SERVER TO CLIENT</dt>
1382 <dd>
1383 <p>The ordering of the returned bundle uris is not significant. Clients
1384 MUST parse their headers to discover their contained OIDS and
1385 prerequisites. A client MUST consider the content of the bundle(s)
1386 themselves and their header as the ultimate source of truth.</p>
1387 <div class="paragraph">
1388 <p>A server MAY even return bundle(s) that don&#8217;t have any direct
1389 relationship to the repository being cloned (either through accident,
1390 or intentional "clever" configuration), and expect a client to sort
1391 out what data they&#8217;d like from the bundle(s), if any.</p>
1392 </div>
1393 </dd>
1394 <dt class="hdlist1">bundle-uri CLIENT TO SERVER</dt>
1395 <dd>
1396 <p>The client SHOULD provide reference tips found in the bundle header(s)
1397 as <em>have</em> lines in any subsequent <code>fetch</code> request. A client MAY also
1398 ignore the bundle(s) entirely if doing so is deemed worse for some
1399 reason, e.g. if the bundles can&#8217;t be downloaded, it doesn&#8217;t like the
1400 tips it finds etc.</p>
1401 </dd>
1402 <dt class="hdlist1">WHEN ADVERTISED BUNDLE(S) REQUIRE NO FURTHER NEGOTIATION</dt>
1403 <dd>
1404 <p>If after issuing <code>bundle-uri</code> and <code>ls-refs</code>, and getting the header(s)
1405 of the bundle(s) the client finds that the ref tips it wants can be
1406 retrieved entirely from advertised bundle(s), the client MAY disconnect
1407 from the Git server. The results of such a <em>clone</em> or <em>fetch</em> should be
1408 indistinguishable from the state attained without using bundle-uri.</p>
1409 </dd>
1410 <dt class="hdlist1">EARLY CLIENT DISCONNECTIONS AND ERROR RECOVERY</dt>
1411 <dd>
1412 <p>A client MAY perform an early disconnect while still downloading the
1413 bundle(s) (having streamed and parsed their headers). In such a case
1414 the client MUST gracefully recover from any errors related to
1415 finishing the download and validation of the bundle(s).</p>
1416 <div class="paragraph">
1417 <p>I.e. a client might need to re-connect and issue a <em>fetch</em> command,
1418 and possibly fall back to not making use of <em>bundle-uri</em> at all.</p>
1419 </div>
1420 <div class="paragraph">
1421 <p>This "MAY" behavior is specified as such (and not a "SHOULD") on the
1422 assumption that a server advertising bundle uris is more likely than
1423 not to be serving up a relatively large repository, and to be pointing
1424 to URIs that have a good chance of being in working order. A client
1425 MAY e.g. look at the payload size of the bundles as a heuristic to see
1426 if an early disconnect is worth it, should falling back on a full
1427 "fetch" dialog be necessary.</p>
1428 </div>
1429 </dd>
1430 <dt class="hdlist1">WHEN ADVERTISED BUNDLE(S) REQUIRE FURTHER NEGOTIATION</dt>
1431 <dd>
1432 <p>A client SHOULD commence a negotiation of a PACK from the server via
1433 the "fetch" command using the OID tips found in advertised bundles,
1434 even if&#8217;s still in the process of downloading those bundle(s).</p>
1435 <div class="paragraph">
1436 <p>This allows for aggressive early disconnects from any interactive
1437 server dialog. The client blindly trusts that the advertised OID tips
1438 are relevant, and issues them as <em>have</em> lines, it then requests any
1439 tips it would like (usually from the "ls-refs" advertisement) via
1440 <em>want</em> lines. The server will then compute a (hopefully small) PACK
1441 with the expected difference between the tips from the bundle(s) and
1442 the data requested.</p>
1443 </div>
1444 <div class="paragraph">
1445 <p>The only connection the client then needs to keep active is to the
1446 concurrently downloading static bundle(s), when those and the
1447 incremental PACK are retrieved they should be inflated and
1448 validated. Any errors at this point should be gracefully recovered
1449 from, see above.</p>
1450 </div>
1451 </dd>
1452 </dl>
1453 </div>
1454 </div>
1455 <div class="sect3">
1456 <h4 id="_bundle_uri_protocol_features">bundle-uri PROTOCOL FEATURES</h4>
1457 <div class="paragraph">
1458 <p>The client constructs a bundle list from the <em>&lt;key&gt;</em><code>=</code><em>&lt;value&gt;</em> pairs
1459 provided by the server. These pairs are part of the <code>bundle.</code>* namespace
1460 as documented in <a href="git-config.html">git-config(1)</a>. In this section, we discuss some
1461 of these keys and describe the actions the client will do in response to
1462 this information.</p>
1463 </div>
1464 <div class="paragraph">
1465 <p>In particular, the <code>bundle.version</code> key specifies an integer value. The
1466 only accepted value at the moment is <code>1</code>, but if the client sees an
1467 unexpected value here then the client MUST ignore the bundle list.</p>
1468 </div>
1469 <div class="paragraph">
1470 <p>As long as <code>bundle.version</code> is understood, all other unknown keys MAY be
1471 ignored by the client. The server will guarantee compatibility with older
1472 clients, though newer clients may be better able to use the extra keys to
1473 minimize downloads.</p>
1474 </div>
1475 <div class="paragraph">
1476 <p>Any backwards-incompatible addition of pre-URI key-value will be
1477 guarded by a new <code>bundle.version</code> value or values in <em>bundle-uri</em>
1478 capability advertisement itself, and/or by new future <code>bundle-uri</code>
1479 request arguments.</p>
1480 </div>
1481 <div class="paragraph">
1482 <p>Some example key-value pairs that are not currently implemented but could
1483 be implemented in the future include:</p>
1484 </div>
1485 <div class="ulist">
1486 <ul>
1487 <li>
1488 <p>Add a "hash=&lt;val&gt;" or "size=&lt;bytes&gt;" advertise the expected hash or
1489 size of the bundle file.</p>
1490 </li>
1491 <li>
1492 <p>Advertise that one or more bundle files are the same (to e.g. have
1493 clients round-robin or otherwise choose one of N possible files).</p>
1494 </li>
1495 <li>
1496 <p>A "oid=&lt;OID&gt;" shortcut and "prerequisite=&lt;OID&gt;" shortcut. For
1497 expressing the common case of a bundle with one tip and no
1498 prerequisites, or one tip and one prerequisite.</p>
1499 <div class="paragraph">
1500 <p>This would allow for optimizing the common case of servers who&#8217;d like
1501 to provide one "big bundle" containing only their "main" branch,
1502 and/or incremental updates thereof.</p>
1503 </div>
1504 <div class="paragraph">
1505 <p>A client receiving such a response MAY assume that they can skip
1506 retrieving the header from a bundle at the indicated URI, and thus
1507 save themselves and the server(s) the request(s) needed to inspect the
1508 headers of that bundle or bundles.</p>
1509 </div>
1510 </li>
1511 </ul>
1512 </div>
1513 </div>
1514 </div>
1515 </div>
1516 </div>
1517 <div class="sect1">
1518 <h2 id="_git">GIT</h2>
1519 <div class="sectionbody">
1520 <div class="paragraph">
1521 <p>Part of the <a href="git.html">git(1)</a> suite</p>
1522 </div>
1523 </div>
1524 </div>
1525 </div>
1526 <div id="footer">
1527 <div id="footer-text">
1528 Last updated 2024-11-01 22:46:55 -0700
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