gitprotocol-v2.html

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 735 <body class="manpage">
 736 <div id="header">
 737 <h1>
 738 gitprotocol-v2(5) Manual Page
 739 </h1>
 740 <h2>NAME</h2>
 741 <div class="sectionbody">
 742 <p>gitprotocol-v2 -
 743    Git Wire Protocol, Version 2
 744 </p>
 745 </div>
 746 </div>
 747 <div id="content">
 748 <div class="sect1">
 749 <h2 id="_synopsis">SYNOPSIS</h2>
 750 <div class="sectionbody">
 751 <div class="verseblock">
 752 <pre class="content">&lt;over-the-wire-protocol&gt;</pre>
 753 <div class="attribution">
 754 </div></div>
 755 </div>
 756 </div>
 757 <div class="sect1">
 758 <h2 id="_description">DESCRIPTION</h2>
 759 <div class="sectionbody">
 760 <div class="paragraph"><p>This document presents a specification for a version 2 of Git&#8217;s wire
 761 protocol.  Protocol v2 will improve upon v1 in the following ways:</p></div>
 762 <div class="ulist"><ul>
 763 <li>
 764 <p>
 765 Instead of multiple service names, multiple commands will be
 766     supported by a single service
 767 </p>
 768 </li>
 769 <li>
 770 <p>
 771 Easily extendable as capabilities are moved into their own section
 772     of the protocol, no longer being hidden behind a NUL byte and
 773     limited by the size of a pkt-line
 774 </p>
 775 </li>
 776 <li>
 777 <p>
 778 Separate out other information hidden behind NUL bytes (e.g. agent
 779     string as a capability and symrefs can be requested using <em>ls-refs</em>)
 780 </p>
 781 </li>
 782 <li>
 783 <p>
 784 Reference advertisement will be omitted unless explicitly requested
 785 </p>
 786 </li>
 787 <li>
 788 <p>
 789 ls-refs command to explicitly request some refs
 790 </p>
 791 </li>
 792 <li>
 793 <p>
 794 Designed with http and stateless-rpc in mind.  With clear flush
 795     semantics the http remote helper can simply act as a proxy
 796 </p>
 797 </li>
 798 </ul></div>
 799 <div class="paragraph"><p>In protocol v2 communication is command oriented.  When first contacting a
 800 server a list of capabilities will be advertised.  Some of these capabilities
 801 will be commands which a client can request be executed.  Once a command
 802 has completed, a client can reuse the connection and request that other
 803 commands be executed.</p></div>
 804 </div>
 805 </div>
 806 <div class="sect1">
 807 <h2 id="_packet_line_framing">Packet-Line Framing</h2>
 808 <div class="sectionbody">
 809 <div class="paragraph"><p>All communication is done using packet-line framing, just as in v1.  See
 810 <a href="gitprotocol-pack.html">gitprotocol-pack(5)</a> and <a href="gitprotocol-common.html">gitprotocol-common(5)</a> for more information.</p></div>
 811 <div class="paragraph"><p>In protocol v2 these special packets will have the following semantics:</p></div>
 812 <div class="ulist"><ul>
 813 <li>
 814 <p>
 815 <em>0000</em> Flush Packet (flush-pkt) - indicates the end of a message
 816 </p>
 817 </li>
 818 <li>
 819 <p>
 820 <em>0001</em> Delimiter Packet (delim-pkt) - separates sections of a message
 821 </p>
 822 </li>
 823 <li>
 824 <p>
 825 <em>0002</em> Response End Packet (response-end-pkt) - indicates the end of a
 826     response for stateless connections
 827 </p>
 828 </li>
 829 </ul></div>
 830 </div>
 831 </div>
 832 <div class="sect1">
 833 <h2 id="_initial_client_request">Initial Client Request</h2>
 834 <div class="sectionbody">
 835 <div class="paragraph"><p>In general a client can request to speak protocol v2 by sending
 836 <code>version=2</code> through the respective side-channel for the transport being
 837 used which inevitably sets <code>GIT_PROTOCOL</code>.  More information can be
 838 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
 839 <code>GIT_PROTOCOL</code> definition in <code>git.txt</code>. In all cases the
 840 response from the server is the capability advertisement.</p></div>
 841 <div class="sect2">
 842 <h3 id="_git_transport">Git Transport</h3>
 843 <div class="paragraph"><p>When using the git:// transport, you can request to use protocol v2 by
 844 sending "version=2" as an extra parameter:</p></div>
 845 <div class="literalblock">
 846 <div class="content">
 847 <pre><code>003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0</code></pre>
 848 </div></div>
 849 </div>
 850 <div class="sect2">
 851 <h3 id="_ssh_and_file_transport">SSH and File Transport</h3>
 852 <div class="paragraph"><p>When using either the ssh:// or file:// transport, the GIT_PROTOCOL
 853 environment variable must be set explicitly to include "version=2".
 854 The server may need to be configured to allow this environment variable
 855 to pass.</p></div>
 856 </div>
 857 <div class="sect2">
 858 <h3 id="_http_transport">HTTP Transport</h3>
 859 <div class="paragraph"><p>When using the http:// or https:// transport a client makes a "smart"
 860 info/refs request as described in <a href="gitprotocol-http.html">gitprotocol-http(5)</a> and requests that
 861 v2 be used by supplying "version=2" in the <code>Git-Protocol</code> header.</p></div>
 862 <div class="literalblock">
 863 <div class="content">
 864 <pre><code>C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0
 865 C: Git-Protocol: version=2</code></pre>
 866 </div></div>
 867 <div class="paragraph"><p>A v2 server would reply:</p></div>
 868 <div class="literalblock">
 869 <div class="content">
 870 <pre><code>S: 200 OK
 871 S: &lt;Some headers&gt;
 872 S: ...
 873 S:
 874 S: 000eversion 2\n
 875 S: &lt;capability-advertisement&gt;</code></pre>
 876 </div></div>
 877 <div class="paragraph"><p>Subsequent requests are then made directly to the service
 878 <code>$GIT_URL/git-upload-pack</code>. (This works the same for git-receive-pack).</p></div>
 879 <div class="paragraph"><p>Uses the <code>--http-backend-info-refs</code> option to
 880 <a href="git-upload-pack.html">git-upload-pack(1)</a>.</p></div>
 881 <div class="paragraph"><p>The server may need to be configured to pass this header&#8217;s contents via
 882 the <code>GIT_PROTOCOL</code> variable. See the discussion in <code>git-http-backend.txt</code>.</p></div>
 883 </div>
 884 </div>
 885 </div>
 886 <div class="sect1">
 887 <h2 id="_capability_advertisement">Capability Advertisement</h2>
 888 <div class="sectionbody">
 889 <div class="paragraph"><p>A server which decides to communicate (based on a request from a client)
 890 using protocol version 2, notifies the client by sending a version string
 891 in its initial response followed by an advertisement of its capabilities.
 892 Each capability is a key with an optional value.  Clients must ignore all
 893 unknown keys.  Semantics of unknown values are left to the definition of
 894 each key.  Some capabilities will describe commands which can be requested
 895 to be executed by the client.</p></div>
 896 <div class="literalblock">
 897 <div class="content">
 898 <pre><code>capability-advertisement = protocol-version
 899                            capability-list
 900                            flush-pkt</code></pre>
 901 </div></div>
 902 <div class="literalblock">
 903 <div class="content">
 904 <pre><code>protocol-version = PKT-LINE("version 2" LF)
 905 capability-list = *capability
 906 capability = PKT-LINE(key[=value] LF)</code></pre>
 907 </div></div>
 908 <div class="literalblock">
 909 <div class="content">
 910 <pre><code>key = 1*(ALPHA | DIGIT | "-_")
 911 value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()&lt;&gt;!@#$%^&amp;*+=:;")</code></pre>
 912 </div></div>
 913 </div>
 914 </div>
 915 <div class="sect1">
 916 <h2 id="_command_request">Command Request</h2>
 917 <div class="sectionbody">
 918 <div class="paragraph"><p>After receiving the capability advertisement, a client can then issue a
 919 request to select the command it wants with any particular capabilities
 920 or arguments.  There is then an optional section where the client can
 921 provide any command specific parameters or queries.  Only a single
 922 command can be requested at a time.</p></div>
 923 <div class="literalblock">
 924 <div class="content">
 925 <pre><code>request = empty-request | command-request
 926 empty-request = flush-pkt
 927 command-request = command
 928                   capability-list
 929                   delim-pkt
 930                   command-args
 931                   flush-pkt
 932 command = PKT-LINE("command=" key LF)
 933 command-args = *command-specific-arg</code></pre>
 934 </div></div>
 935 <div class="literalblock">
 936 <div class="content">
 937 <pre><code>command-specific-args are packet line framed arguments defined by
 938 each individual command.</code></pre>
 939 </div></div>
 940 <div class="paragraph"><p>The server will then check to ensure that the client&#8217;s request is
 941 comprised of a valid command as well as valid capabilities which were
 942 advertised.  If the request is valid the server will then execute the
 943 command.  A server MUST wait till it has received the client&#8217;s entire
 944 request before issuing a response.  The format of the response is
 945 determined by the command being executed, but in all cases a flush-pkt
 946 indicates the end of the response.</p></div>
 947 <div class="paragraph"><p>When a command has finished, and the client has received the entire
 948 response from the server, a client can either request that another
 949 command be executed or can terminate the connection.  A client may
 950 optionally send an empty request consisting of just a flush-pkt to
 951 indicate that no more requests will be made.</p></div>
 952 </div>
 953 </div>
 954 <div class="sect1">
 955 <h2 id="_capabilities">Capabilities</h2>
 956 <div class="sectionbody">
 957 <div class="paragraph"><p>There are two different types of capabilities: normal capabilities,
 958 which can be used to convey information or alter the behavior of a
 959 request, and commands, which are the core actions that a client wants to
 960 perform (fetch, push, etc).</p></div>
 961 <div class="paragraph"><p>Protocol version 2 is stateless by default.  This means that all commands
 962 must only last a single round and be stateless from the perspective of the
 963 server side, unless the client has requested a capability indicating that
 964 state should be maintained by the server.  Clients MUST NOT require state
 965 management on the server side in order to function correctly.  This
 966 permits simple round-robin load-balancing on the server side, without
 967 needing to worry about state management.</p></div>
 968 <div class="sect2">
 969 <h3 id="_agent">agent</h3>
 970 <div class="paragraph"><p>The server can advertise the <code>agent</code> capability with a value <code>X</code> (in the
 971 form <code>agent=X</code>) to notify the client that the server is running version
 972 <code>X</code>.  The client may optionally send its own agent string by including
 973 the <code>agent</code> capability with a value <code>Y</code> (in the form <code>agent=Y</code>) in its
 974 request to the server (but it MUST NOT do so if the server did not
 975 advertise the agent capability). The <code>X</code> and <code>Y</code> strings may contain any
 976 printable ASCII characters except space (i.e., the byte range 32 &lt; x &lt;
 977 127), and are typically of the form "package/version" (e.g.,
 978 "git/1.8.3.1"). The agent strings are purely informative for statistics
 979 and debugging purposes, and MUST NOT be used to programmatically assume
 980 the presence or absence of particular features.</p></div>
 981 </div>
 982 <div class="sect2">
 983 <h3 id="_ls_refs">ls-refs</h3>
 984 <div class="paragraph"><p><code>ls-refs</code> is the command used to request a reference advertisement in v2.
 985 Unlike the current reference advertisement, ls-refs takes in arguments
 986 which can be used to limit the refs sent from the server.</p></div>
 987 <div class="paragraph"><p>Additional features not supported in the base command will be advertised
 988 as the value of the command in the capability advertisement in the form
 989 of a space separated list of features: "&lt;command&gt;=&lt;feature 1&gt; &lt;feature 2&gt;"</p></div>
 990 <div class="paragraph"><p>ls-refs takes in the following arguments:</p></div>
 991 <div class="literalblock">
 992 <div class="content">
 993 <pre><code>symrefs
 994     In addition to the object pointed by it, show the underlying ref
 995     pointed by it when showing a symbolic ref.
 996 peel
 997     Show peeled tags.
 998 ref-prefix &lt;prefix&gt;
 999     When specified, only references having a prefix matching one of
1000     the provided prefixes are displayed. Multiple instances may be
1001     given, in which case references matching any prefix will be
1002     shown. Note that this is purely for optimization; a server MAY
1003     show refs not matching the prefix if it chooses, and clients
1004     should filter the result themselves.</code></pre>
1005 </div></div>
1006 <div class="paragraph"><p>If the <em>unborn</em> feature is advertised the following argument can be
1007 included in the client&#8217;s request.</p></div>
1008 <div class="literalblock">
1009 <div class="content">
1010 <pre><code>unborn
1011     The server will send information about HEAD even if it is a symref
1012     pointing to an unborn branch in the form "unborn HEAD
1013     symref-target:&lt;target&gt;".</code></pre>
1014 </div></div>
1015 <div class="paragraph"><p>The output of ls-refs is as follows:</p></div>
1016 <div class="literalblock">
1017 <div class="content">
1018 <pre><code>output = *ref
1019          flush-pkt
1020 obj-id-or-unborn = (obj-id | "unborn")
1021 ref = PKT-LINE(obj-id-or-unborn SP refname *(SP ref-attribute) LF)
1022 ref-attribute = (symref | peeled)
1023 symref = "symref-target:" symref-target
1024 peeled = "peeled:" obj-id</code></pre>
1025 </div></div>
1026 </div>
1027 <div class="sect2">
1028 <h3 id="_fetch">fetch</h3>
1029 <div class="paragraph"><p><code>fetch</code> is the command used to fetch a packfile in v2.  It can be looked
1030 at as a modified version of the v1 fetch where the ref-advertisement is
1031 stripped out (since the <code>ls-refs</code> command fills that role) and the
1032 message format is tweaked to eliminate redundancies and permit easy
1033 addition of future extensions.</p></div>
1034 <div class="paragraph"><p>Additional features not supported in the base command will be advertised
1035 as the value of the command in the capability advertisement in the form
1036 of a space separated list of features: "&lt;command&gt;=&lt;feature 1&gt; &lt;feature 2&gt;"</p></div>
1037 <div class="paragraph"><p>A <code>fetch</code> request can take the following arguments:</p></div>
1038 <div class="literalblock">
1039 <div class="content">
1040 <pre><code>want &lt;oid&gt;
1041     Indicates to the server an object which the client wants to
1042     retrieve.  Wants can be anything and are not limited to
1043     advertised objects.</code></pre>
1044 </div></div>
1045 <div class="literalblock">
1046 <div class="content">
1047 <pre><code>have &lt;oid&gt;
1048     Indicates to the server an object which the client has locally.
1049     This allows the server to make a packfile which only contains
1050     the objects that the client needs. Multiple 'have' lines can be
1051     supplied.</code></pre>
1052 </div></div>
1053 <div class="literalblock">
1054 <div class="content">
1055 <pre><code>done
1056     Indicates to the server that negotiation should terminate (or
1057     not even begin if performing a clone) and that the server should
1058     use the information supplied in the request to construct the
1059     packfile.</code></pre>
1060 </div></div>
1061 <div class="literalblock">
1062 <div class="content">
1063 <pre><code>thin-pack
1064     Request that a thin pack be sent, which is a pack with deltas
1065     which reference base objects not contained within the pack (but
1066     are known to exist at the receiving end). This can reduce the
1067     network traffic significantly, but it requires the receiving end
1068     to know how to "thicken" these packs by adding the missing bases
1069     to the pack.</code></pre>
1070 </div></div>
1071 <div class="literalblock">
1072 <div class="content">
1073 <pre><code>no-progress
1074     Request that progress information that would normally be sent on
1075     side-band channel 2, during the packfile transfer, should not be
1076     sent.  However, the side-band channel 3 is still used for error
1077     responses.</code></pre>
1078 </div></div>
1079 <div class="literalblock">
1080 <div class="content">
1081 <pre><code>include-tag
1082     Request that annotated tags should be sent if the objects they
1083     point to are being sent.</code></pre>
1084 </div></div>
1085 <div class="literalblock">
1086 <div class="content">
1087 <pre><code>ofs-delta
1088     Indicate that the client understands PACKv2 with delta referring
1089     to its base by position in pack rather than by an oid.  That is,
1090     they can read OBJ_OFS_DELTA (aka type 6) in a packfile.</code></pre>
1091 </div></div>
1092 <div class="paragraph"><p>If the <em>shallow</em> feature is advertised the following arguments can be
1093 included in the clients request as well as the potential addition of the
1094 <em>shallow-info</em> section in the server&#8217;s response as explained below.</p></div>
1095 <div class="literalblock">
1096 <div class="content">
1097 <pre><code>shallow &lt;oid&gt;
1098     A client must notify the server of all commits for which it only
1099     has shallow copies (meaning that it doesn't have the parents of
1100     a commit) by supplying a 'shallow &lt;oid&gt;' line for each such
1101     object so that the server is aware of the limitations of the
1102     client's history.  This is so that the server is aware that the
1103     client may not have all objects reachable from such commits.</code></pre>
1104 </div></div>
1105 <div class="literalblock">
1106 <div class="content">
1107 <pre><code>deepen &lt;depth&gt;
1108     Requests that the fetch/clone should be shallow having a commit
1109     depth of &lt;depth&gt; relative to the remote side.</code></pre>
1110 </div></div>
1111 <div class="literalblock">
1112 <div class="content">
1113 <pre><code>deepen-relative
1114     Requests that the semantics of the "deepen" command be changed
1115     to indicate that the depth requested is relative to the client's
1116     current shallow boundary, instead of relative to the requested
1117     commits.</code></pre>
1118 </div></div>
1119 <div class="literalblock">
1120 <div class="content">
1121 <pre><code>deepen-since &lt;timestamp&gt;
1122     Requests that the shallow clone/fetch should be cut at a
1123     specific time, instead of depth.  Internally it's equivalent to
1124     doing "git rev-list --max-age=&lt;timestamp&gt;". Cannot be used with
1125     "deepen".</code></pre>
1126 </div></div>
1127 <div class="literalblock">
1128 <div class="content">
1129 <pre><code>deepen-not &lt;rev&gt;
1130     Requests that the shallow clone/fetch should be cut at a
1131     specific revision specified by '&lt;rev&gt;', instead of a depth.
1132     Internally it's equivalent of doing "git rev-list --not &lt;rev&gt;".
1133     Cannot be used with "deepen", but can be used with
1134     "deepen-since".</code></pre>
1135 </div></div>
1136 <div class="paragraph"><p>If the <em>filter</em> feature is advertised, the following argument can be
1137 included in the client&#8217;s request:</p></div>
1138 <div class="literalblock">
1139 <div class="content">
1140 <pre><code>filter &lt;filter-spec&gt;
1141     Request that various objects from the packfile be omitted
1142     using one of several filtering techniques. These are intended
1143     for use with partial clone and partial fetch operations. See
1144     `rev-list` for possible "filter-spec" values. When communicating
1145     with other processes, senders SHOULD translate scaled integers
1146     (e.g. "1k") into a fully-expanded form (e.g. "1024") to aid
1147     interoperability with older receivers that may not understand
1148     newly-invented scaling suffixes. However, receivers SHOULD
1149     accept the following suffixes: 'k', 'm', and 'g' for 1024,
1150     1048576, and 1073741824, respectively.</code></pre>
1151 </div></div>
1152 <div class="paragraph"><p>If the <em>ref-in-want</em> feature is advertised, the following argument can
1153 be included in the client&#8217;s request as well as the potential addition of
1154 the <em>wanted-refs</em> section in the server&#8217;s response as explained below.</p></div>
1155 <div class="literalblock">
1156 <div class="content">
1157 <pre><code>want-ref &lt;ref&gt;
1158     Indicates to the server that the client wants to retrieve a
1159     particular ref, where &lt;ref&gt; is the full name of a ref on the
1160     server.</code></pre>
1161 </div></div>
1162 <div class="paragraph"><p>If the <em>sideband-all</em> feature is advertised, the following argument can be
1163 included in the client&#8217;s request:</p></div>
1164 <div class="literalblock">
1165 <div class="content">
1166 <pre><code>sideband-all
1167     Instruct the server to send the whole response multiplexed, not just
1168     the packfile section. All non-flush and non-delim PKT-LINE in the
1169     response (not only in the packfile section) will then start with a byte
1170     indicating its sideband (1, 2, or 3), and the server may send "0005\2"
1171     (a PKT-LINE of sideband 2 with no payload) as a keepalive packet.</code></pre>
1172 </div></div>
1173 <div class="paragraph"><p>If the <em>packfile-uris</em> feature is advertised, the following argument
1174 can be included in the client&#8217;s request as well as the potential
1175 addition of the <em>packfile-uris</em> section in the server&#8217;s response as
1176 explained below.</p></div>
1177 <div class="literalblock">
1178 <div class="content">
1179 <pre><code>packfile-uris &lt;comma-separated list of protocols&gt;
1180     Indicates to the server that the client is willing to receive
1181     URIs of any of the given protocols in place of objects in the
1182     sent packfile. Before performing the connectivity check, the
1183     client should download from all given URIs. Currently, the
1184     protocols supported are "http" and "https".</code></pre>
1185 </div></div>
1186 <div class="paragraph"><p>If the <em>wait-for-done</em> feature is advertised, the following argument
1187 can be included in the client&#8217;s request.</p></div>
1188 <div class="literalblock">
1189 <div class="content">
1190 <pre><code>wait-for-done
1191     Indicates to the server that it should never send "ready", but
1192     should wait for the client to say "done" before sending the
1193     packfile.</code></pre>
1194 </div></div>
1195 <div class="paragraph"><p>The response of <code>fetch</code> is broken into a number of sections separated by
1196 delimiter packets (0001), with each section beginning with its section
1197 header. Most sections are sent only when the packfile is sent.</p></div>
1198 <div class="literalblock">
1199 <div class="content">
1200 <pre><code>output = acknowledgements flush-pkt |
1201          [acknowledgments delim-pkt] [shallow-info delim-pkt]
1202          [wanted-refs delim-pkt] [packfile-uris delim-pkt]
1203          packfile flush-pkt</code></pre>
1204 </div></div>
1205 <div class="literalblock">
1206 <div class="content">
1207 <pre><code>acknowledgments = PKT-LINE("acknowledgments" LF)
1208                   (nak | *ack)
1209                   (ready)
1210 ready = PKT-LINE("ready" LF)
1211 nak = PKT-LINE("NAK" LF)
1212 ack = PKT-LINE("ACK" SP obj-id LF)</code></pre>
1213 </div></div>
1214 <div class="literalblock">
1215 <div class="content">
1216 <pre><code>shallow-info = PKT-LINE("shallow-info" LF)
1217                *PKT-LINE((shallow | unshallow) LF)
1218 shallow = "shallow" SP obj-id
1219 unshallow = "unshallow" SP obj-id</code></pre>
1220 </div></div>
1221 <div class="literalblock">
1222 <div class="content">
1223 <pre><code>wanted-refs = PKT-LINE("wanted-refs" LF)
1224               *PKT-LINE(wanted-ref LF)
1225 wanted-ref = obj-id SP refname</code></pre>
1226 </div></div>
1227 <div class="literalblock">
1228 <div class="content">
1229 <pre><code>packfile-uris = PKT-LINE("packfile-uris" LF) *packfile-uri
1230 packfile-uri = PKT-LINE(40*(HEXDIGIT) SP *%x20-ff LF)</code></pre>
1231 </div></div>
1232 <div class="literalblock">
1233 <div class="content">
1234 <pre><code>packfile = PKT-LINE("packfile" LF)
1235            *PKT-LINE(%x01-03 *%x00-ff)</code></pre>
1236 </div></div>
1237 <div class="literalblock">
1238 <div class="content">
1239 <pre><code>acknowledgments section
1240     * If the client determines that it is finished with negotiations by
1241       sending a "done" line (thus requiring the server to send a packfile),
1242       the acknowledgments sections MUST be omitted from the server's
1243       response.</code></pre>
1244 </div></div>
1245 <div class="ulist"><ul>
1246 <li>
1247 <p>
1248 Always begins with the section header "acknowledgments"
1249 </p>
1250 </li>
1251 <li>
1252 <p>
1253 The server will respond with "NAK" if none of the object ids sent
1254           as have lines were common.
1255 </p>
1256 </li>
1257 <li>
1258 <p>
1259 The server will respond with "ACK obj-id" for all of the
1260           object ids sent as have lines which are common.
1261 </p>
1262 </li>
1263 <li>
1264 <p>
1265 A response cannot have both "ACK" lines as well as a "NAK"
1266           line.
1267 </p>
1268 </li>
1269 <li>
1270 <p>
1271 The server will respond with a "ready" line indicating that
1272           the server has found an acceptable common base and is ready to
1273           make and send a packfile (which will be found in the packfile
1274           section of the same response)
1275 </p>
1276 </li>
1277 <li>
1278 <p>
1279 If the server has found a suitable cut point and has decided
1280           to send a "ready" line, then the server can decide to (as an
1281           optimization) omit any "ACK" lines it would have sent during
1282           its response.  This is because the server will have already
1283           determined the objects it plans to send to the client and no
1284           further negotiation is needed.
1285 </p>
1286 <div class="literalblock">
1287 <div class="content">
1288 <pre><code>shallow-info section
1289     * If the client has requested a shallow fetch/clone, a shallow
1290       client requests a fetch or the server is shallow then the
1291       server's response may include a shallow-info section.  The
1292       shallow-info section will be included if (due to one of the
1293       above conditions) the server needs to inform the client of any
1294       shallow boundaries or adjustments to the clients already
1295       existing shallow boundaries.</code></pre>
1296 </div></div>
1297 </li>
1298 <li>
1299 <p>
1300 Always begins with the section header "shallow-info"
1301 </p>
1302 </li>
1303 <li>
1304 <p>
1305 If a positive depth is requested, the server will compute the
1306           set of commits which are no deeper than the desired depth.
1307 </p>
1308 </li>
1309 <li>
1310 <p>
1311 The server sends a "shallow obj-id" line for each commit whose
1312           parents will not be sent in the following packfile.
1313 </p>
1314 </li>
1315 <li>
1316 <p>
1317 The server sends an "unshallow obj-id" line for each commit
1318           which the client has indicated is shallow, but is no longer
1319           shallow as a result of the fetch (due to its parents being
1320           sent in the following packfile).
1321 </p>
1322 </li>
1323 <li>
1324 <p>
1325 The server MUST NOT send any "unshallow" lines for anything
1326           which the client has not indicated was shallow as a part of
1327           its request.
1328 </p>
1329 <div class="literalblock">
1330 <div class="content">
1331 <pre><code>wanted-refs section
1332     * This section is only included if the client has requested a
1333       ref using a 'want-ref' line and if a packfile section is also
1334       included in the response.</code></pre>
1335 </div></div>
1336 </li>
1337 <li>
1338 <p>
1339 Always begins with the section header "wanted-refs".
1340 </p>
1341 </li>
1342 <li>
1343 <p>
1344 The server will send a ref listing ("&lt;oid&gt; &lt;refname&gt;") for
1345           each reference requested using <em>want-ref</em> lines.
1346 </p>
1347 </li>
1348 <li>
1349 <p>
1350 The server MUST NOT send any refs which were not requested
1351           using <em>want-ref</em> lines.
1352 </p>
1353 <div class="literalblock">
1354 <div class="content">
1355 <pre><code>packfile-uris section
1356     * This section is only included if the client sent
1357       'packfile-uris' and the server has at least one such URI to
1358       send.</code></pre>
1359 </div></div>
1360 </li>
1361 <li>
1362 <p>
1363 Always begins with the section header "packfile-uris".
1364 </p>
1365 </li>
1366 <li>
1367 <p>
1368 For each URI the server sends, it sends a hash of the pack&#8217;s
1369           contents (as output by git index-pack) followed by the URI.
1370 </p>
1371 </li>
1372 <li>
1373 <p>
1374 The hashes are 40 hex characters long. When Git upgrades to a new
1375           hash algorithm, this might need to be updated. (It should match
1376           whatever index-pack outputs after "pack\t" or "keep\t".
1377 </p>
1378 <div class="literalblock">
1379 <div class="content">
1380 <pre><code>packfile section
1381     * This section is only included if the client has sent 'want'
1382       lines in its request and either requested that no more
1383       negotiation be done by sending 'done' or if the server has
1384       decided it has found a sufficient cut point to produce a
1385       packfile.</code></pre>
1386 </div></div>
1387 </li>
1388 <li>
1389 <p>
1390 Always begins with the section header "packfile"
1391 </p>
1392 </li>
1393 <li>
1394 <p>
1395 The transmission of the packfile begins immediately after the
1396           section header
1397 </p>
1398 </li>
1399 <li>
1400 <p>
1401 The data transfer of the packfile is always multiplexed, using
1402           the same semantics of the <em>side-band-64k</em> capability from
1403           protocol version 1.  This means that each packet, during the
1404           packfile data stream, is made up of a leading 4-byte pkt-line
1405           length (typical of the pkt-line format), followed by a 1-byte
1406           stream code, followed by the actual data.
1407 </p>
1408 <div class="literalblock">
1409 <div class="content">
1410 <pre><code>The stream code can be one of:
1411       1 - pack data
1412       2 - progress messages
1413       3 - fatal error message just before stream aborts</code></pre>
1414 </div></div>
1415 </li>
1416 </ul></div>
1417 </div>
1418 <div class="sect2">
1419 <h3 id="_server_option">server-option</h3>
1420 <div class="paragraph"><p>If advertised, indicates that any number of server specific options can be
1421 included in a request.  This is done by sending each option as a
1422 "server-option=&lt;option&gt;" capability line in the capability-list section of
1423 a request.</p></div>
1424 <div class="paragraph"><p>The provided options must not contain a NUL or LF character.</p></div>
1425 </div>
1426 <div class="sect2">
1427 <h3 id="_object_format"> object-format</h3>
1428 <div class="paragraph"><p>The server can advertise the <code>object-format</code> capability with a value <code>X</code> (in the
1429 form <code>object-format=X</code>) to notify the client that the server is able to deal
1430 with objects using hash algorithm X.  If not specified, the server is assumed to
1431 only handle SHA-1.  If the client would like to use a hash algorithm other than
1432 SHA-1, it should specify its object-format string.</p></div>
1433 </div>
1434 <div class="sect2">
1435 <h3 id="_session_id_lt_session_id_gt">session-id=&lt;session id&gt;</h3>
1436 <div class="paragraph"><p>The server may advertise a session ID that can be used to identify this process
1437 across multiple requests. The client may advertise its own session ID back to
1438 the server as well.</p></div>
1439 <div class="paragraph"><p>Session IDs should be unique to a given process. They must fit within a
1440 packet-line, and must not contain non-printable or whitespace characters. The
1441 current implementation uses trace2 session IDs (see
1442 <a href="technical/api-trace2.html">api-trace2</a> for details), but this may change
1443 and users of the session ID should not rely on this fact.</p></div>
1444 </div>
1445 <div class="sect2">
1446 <h3 id="_object_info">object-info</h3>
1447 <div class="paragraph"><p><code>object-info</code> is the command to retrieve information about one or more objects.
1448 Its main purpose is to allow a client to make decisions based on this
1449 information without having to fully fetch objects. Object size is the only
1450 information that is currently supported.</p></div>
1451 <div class="paragraph"><p>An <code>object-info</code> request takes the following arguments:</p></div>
1452 <div class="literalblock">
1453 <div class="content">
1454 <pre><code>size
1455 Requests size information to be returned for each listed object id.</code></pre>
1456 </div></div>
1457 <div class="literalblock">
1458 <div class="content">
1459 <pre><code>oid &lt;oid&gt;
1460 Indicates to the server an object which the client wants to obtain
1461 information for.</code></pre>
1462 </div></div>
1463 <div class="paragraph"><p>The response of <code>object-info</code> is a list of the requested object ids
1464 and associated requested information, each separated by a single space.</p></div>
1465 <div class="literalblock">
1466 <div class="content">
1467 <pre><code>output = info flush-pkt</code></pre>
1468 </div></div>
1469 <div class="literalblock">
1470 <div class="content">
1471 <pre><code>info = PKT-LINE(attrs) LF)
1472         *PKT-LINE(obj-info LF)</code></pre>
1473 </div></div>
1474 <div class="literalblock">
1475 <div class="content">
1476 <pre><code>attrs = attr | attrs SP attrs</code></pre>
1477 </div></div>
1478 <div class="literalblock">
1479 <div class="content">
1480 <pre><code>attr = "size"</code></pre>
1481 </div></div>
1482 <div class="literalblock">
1483 <div class="content">
1484 <pre><code>obj-info = obj-id SP obj-size</code></pre>
1485 </div></div>
1486 </div>
1487 <div class="sect2">
1488 <h3 id="_bundle_uri">bundle-uri</h3>
1489 <div class="paragraph"><p>If the <em>bundle-uri</em> capability is advertised, the server supports the
1490 &#8216;bundle-uri&#8217; command.</p></div>
1491 <div class="paragraph"><p>The capability is currently advertised with no value (i.e. not
1492 "bundle-uri=somevalue"), a value may be added in the future for
1493 supporting command-wide extensions. Clients MUST ignore any unknown
1494 capability values and proceed with the 'bundle-uri` dialog they
1495 support.</p></div>
1496 <div class="paragraph"><p>The <em>bundle-uri</em> command is intended to be issued before <code>fetch</code> to
1497 get URIs to bundle files (see <a href="git-bundle.html">git-bundle(1)</a>) to "seed" and
1498 inform the subsequent <code>fetch</code> command.</p></div>
1499 <div class="paragraph"><p>The client CAN issue <code>bundle-uri</code> before or after any other valid
1500 command. To be useful to clients it&#8217;s expected that it&#8217;ll be issued
1501 after an <code>ls-refs</code> and before <code>fetch</code>, but CAN be issued at any time
1502 in the dialog.</p></div>
1503 <div class="sect3">
1504 <h4 id="_discussion_of_bundle_uri">DISCUSSION of bundle-uri</h4>
1505 <div class="paragraph"><p>The intent of the feature is optimize for server resource consumption
1506 in the common case by changing the common case of fetching a very
1507 large PACK during <a href="git-clone.html">git-clone(1)</a> into a smaller incremental
1508 fetch.</p></div>
1509 <div class="paragraph"><p>It also allows servers to achieve better caching in combination with
1510 an <code>uploadpack.packObjectsHook</code> (see <a href="git-config.html">git-config(1)</a>).</p></div>
1511 <div class="paragraph"><p>By having new clones or fetches be a more predictable and common
1512 negotiation against the tips of recently produces *.bundle file(s).
1513 Servers might even pre-generate the results of such negotiations for
1514 the <code>uploadpack.packObjectsHook</code> as new pushes come in.</p></div>
1515 <div class="paragraph"><p>One way that servers could take advantage of these bundles is that the
1516 server would anticipate that fresh clones will download a known bundle,
1517 followed by catching up to the current state of the repository using ref
1518 tips found in that bundle (or bundles).</p></div>
1519 </div>
1520 <div class="sect3">
1521 <h4 id="_protocol_for_bundle_uri">PROTOCOL for bundle-uri</h4>
1522 <div class="paragraph"><p>A <code>bundle-uri</code> request takes no arguments, and as noted above does not
1523 currently advertise a capability value. Both may be added in the
1524 future.</p></div>
1525 <div class="paragraph"><p>When the client issues a <code>command=bundle-uri</code> request, the response is a
1526 list of key-value pairs provided as packet lines with value
1527 <code>&lt;key&gt;=&lt;value&gt;</code>. Each <code>&lt;key&gt;</code> should be interpreted as a config key from
1528 the <code>bundle.*</code> namespace to construct a list of bundles. These keys are
1529 grouped by a <code>bundle.&lt;id&gt;.</code> subsection, where each key corresponding to a
1530 given <code>&lt;id&gt;</code> contributes attributes to the bundle defined by that <code>&lt;id&gt;</code>.
1531 See <a href="git-config.html">git-config(1)</a> for the specific details of these keys and how
1532 the Git client will interpret their values.</p></div>
1533 <div class="paragraph"><p>Clients MUST parse the line according to the above format, lines that do
1534 not conform to the format SHOULD be discarded. The user MAY be warned in
1535 such a case.</p></div>
1536 </div>
1537 <div class="sect3">
1538 <h4 id="_bundle_uri_client_and_server_expectations">bundle-uri CLIENT AND SERVER EXPECTATIONS</h4>
1539 <div class="dlist"><dl>
1540 <dt class="hdlist1">
1541 URI CONTENTS
1542 </dt>
1543 <dd>
1544 <p>
1545 The content at the advertised URIs MUST be one of two types.
1546 </p>
1547 <div class="paragraph"><p>The advertised URI may contain a bundle file that <code>git bundle verify</code>
1548 would accept. I.e. they MUST contain one or more reference tips for
1549 use by the client, MUST indicate prerequisites (in any) with standard
1550 "-" prefixes, and MUST indicate their "object-format", if
1551 applicable.</p></div>
1552 <div class="paragraph"><p>The advertised URI may alternatively contain a plaintext file that <code>git
1553 config --list</code> would accept (with the <code>--file</code> option). The key-value
1554 pairs in this list are in the <code>bundle.*</code> namespace (see
1555 <a href="git-config.html">git-config(1)</a>).</p></div>
1556 </dd>
1557 <dt class="hdlist1">
1558 bundle-uri CLIENT ERROR RECOVERY
1559 </dt>
1560 <dd>
1561 <p>
1562 A client MUST above all gracefully degrade on errors, whether that
1563 error is because of bad missing/data in the bundle URI(s), because
1564 that client is too dumb to e.g. understand and fully parse out bundle
1565 headers and their prerequisite relationships, or something else.
1566 </p>
1567 <div class="paragraph"><p>Server operators should feel confident in turning on "bundle-uri" and
1568 not worry if e.g. their CDN goes down that clones or fetches will run
1569 into hard failures. Even if the server bundle(s) are
1570 incomplete, or bad in some way the client should still end up with a
1571 functioning repository, just as if it had chosen not to use this
1572 protocol extension.</p></div>
1573 <div class="paragraph"><p>All subsequent discussion on client and server interaction MUST keep
1574 this in mind.</p></div>
1575 </dd>
1576 <dt class="hdlist1">
1577 bundle-uri SERVER TO CLIENT
1578 </dt>
1579 <dd>
1580 <p>
1581 The ordering of the returned bundle uris is not significant. Clients
1582 MUST parse their headers to discover their contained OIDS and
1583 prerequisites. A client MUST consider the content of the bundle(s)
1584 themselves and their header as the ultimate source of truth.
1585 </p>
1586 <div class="paragraph"><p>A server MAY even return bundle(s) that don&#8217;t have any direct
1587 relationship to the repository being cloned (either through accident,
1588 or intentional "clever" configuration), and expect a client to sort
1589 out what data they&#8217;d like from the bundle(s), if any.</p></div>
1590 </dd>
1591 <dt class="hdlist1">
1592 bundle-uri CLIENT TO SERVER
1593 </dt>
1594 <dd>
1595 <p>
1596 The client SHOULD provide reference tips found in the bundle header(s)
1597 as <em>have</em> lines in any subsequent <code>fetch</code> request. A client MAY also
1598 ignore the bundle(s) entirely if doing so is deemed worse for some
1599 reason, e.g. if the bundles can&#8217;t be downloaded, it doesn&#8217;t like the
1600 tips it finds etc.
1601 </p>
1602 </dd>
1603 <dt class="hdlist1">
1604 WHEN ADVERTISED BUNDLE(S) REQUIRE NO FURTHER NEGOTIATION
1605 </dt>
1606 <dd>
1607 <p>
1608 If after issuing <code>bundle-uri</code> and <code>ls-refs</code>, and getting the header(s)
1609 of the bundle(s) the client finds that the ref tips it wants can be
1610 retrieved entirely from advertised bundle(s), the client MAY disconnect
1611 from the Git server. The results of such a <em>clone</em> or <em>fetch</em> should be
1612 indistinguishable from the state attained without using bundle-uri.
1613 </p>
1614 </dd>
1615 <dt class="hdlist1">
1616 EARLY CLIENT DISCONNECTIONS AND ERROR RECOVERY
1617 </dt>
1618 <dd>
1619 <p>
1620 A client MAY perform an early disconnect while still downloading the
1621 bundle(s) (having streamed and parsed their headers). In such a case
1622 the client MUST gracefully recover from any errors related to
1623 finishing the download and validation of the bundle(s).
1624 </p>
1625 <div class="paragraph"><p>I.e. a client might need to re-connect and issue a <em>fetch</em> command,
1626 and possibly fall back to not making use of <em>bundle-uri</em> at all.</p></div>
1627 <div class="paragraph"><p>This "MAY" behavior is specified as such (and not a "SHOULD") on the
1628 assumption that a server advertising bundle uris is more likely than
1629 not to be serving up a relatively large repository, and to be pointing
1630 to URIs that have a good chance of being in working order. A client
1631 MAY e.g. look at the payload size of the bundles as a heuristic to see
1632 if an early disconnect is worth it, should falling back on a full
1633 "fetch" dialog be necessary.</p></div>
1634 </dd>
1635 <dt class="hdlist1">
1636 WHEN ADVERTISED BUNDLE(S) REQUIRE FURTHER NEGOTIATION
1637 </dt>
1638 <dd>
1639 <p>
1640 A client SHOULD commence a negotiation of a PACK from the server via
1641 the "fetch" command using the OID tips found in advertised bundles,
1642 even if&#8217;s still in the process of downloading those bundle(s).
1643 </p>
1644 <div class="paragraph"><p>This allows for aggressive early disconnects from any interactive
1645 server dialog. The client blindly trusts that the advertised OID tips
1646 are relevant, and issues them as <em>have</em> lines, it then requests any
1647 tips it would like (usually from the "ls-refs" advertisement) via
1648 <em>want</em> lines. The server will then compute a (hopefully small) PACK
1649 with the expected difference between the tips from the bundle(s) and
1650 the data requested.</p></div>
1651 <div class="paragraph"><p>The only connection the client then needs to keep active is to the
1652 concurrently downloading static bundle(s), when those and the
1653 incremental PACK are retrieved they should be inflated and
1654 validated. Any errors at this point should be gracefully recovered
1655 from, see above.</p></div>
1656 </dd>
1657 </dl></div>
1658 </div>
1659 <div class="sect3">
1660 <h4 id="_bundle_uri_protocol_features">bundle-uri PROTOCOL FEATURES</h4>
1661 <div class="paragraph"><p>The client constructs a bundle list from the <code>&lt;key&gt;=&lt;value&gt;</code> pairs
1662 provided by the server. These pairs are part of the <code>bundle.*</code> namespace
1663 as documented in <a href="git-config.html">git-config(1)</a>. In this section, we discuss some
1664 of these keys and describe the actions the client will do in response to
1665 this information.</p></div>
1666 <div class="paragraph"><p>In particular, the <code>bundle.version</code> key specifies an integer value. The
1667 only accepted value at the moment is <code>1</code>, but if the client sees an
1668 unexpected value here then the client MUST ignore the bundle list.</p></div>
1669 <div class="paragraph"><p>As long as <code>bundle.version</code> is understood, all other unknown keys MAY be
1670 ignored by the client. The server will guarantee compatibility with older
1671 clients, though newer clients may be better able to use the extra keys to
1672 minimize downloads.</p></div>
1673 <div class="paragraph"><p>Any backwards-incompatible addition of pre-URI key-value will be
1674 guarded by a new <code>bundle.version</code> value or values in <em>bundle-uri</em>
1675 capability advertisement itself, and/or by new future <code>bundle-uri</code>
1676 request arguments.</p></div>
1677 <div class="paragraph"><p>Some example key-value pairs that are not currently implemented but could
1678 be implemented in the future include:</p></div>
1679 <div class="ulist"><ul>
1680 <li>
1681 <p>
1682 Add a "hash=&lt;val&gt;" or "size=&lt;bytes&gt;" advertise the expected hash or
1683    size of the bundle file.
1684 </p>
1685 </li>
1686 <li>
1687 <p>
1688 Advertise that one or more bundle files are the same (to e.g. have
1689    clients round-robin or otherwise choose one of N possible files).
1690 </p>
1691 </li>
1692 <li>
1693 <p>
1694 A "oid=&lt;OID&gt;" shortcut and "prerequisite=&lt;OID&gt;" shortcut. For
1695    expressing the common case of a bundle with one tip and no
1696    prerequisites, or one tip and one prerequisite.
1697 </p>
1698 <div class="paragraph"><p>This would allow for optimizing the common case of servers who&#8217;d like
1699 to provide one "big bundle" containing only their "main" branch,
1700 and/or incremental updates thereof.</p></div>
1701 <div class="paragraph"><p>A client receiving such a a response MAY assume that they can skip
1702 retrieving the header from a bundle at the indicated URI, and thus
1703 save themselves and the server(s) the request(s) needed to inspect the
1704 headers of that bundle or bundles.</p></div>
1705 </li>
1706 </ul></div>
1707 </div>
1708 </div>
1709 </div>
1710 </div>
1711 <div class="sect1">
1712 <h2 id="_git">GIT</h2>
1713 <div class="sectionbody">
1714 <div class="paragraph"><p>Part of the <a href="git.html">git(1)</a> suite</p></div>
1715 </div>
1716 </div>
1717 </div>
1718 <div id="footnotes"><hr /></div>
1719 <div id="footer">
1720 <div id="footer-text">
1721 Last updated
1722  2023-10-23 14:43:46 PDT
1723 </div>
1724 </div>
1725 </body>
1726 </html>