]>
Commit | Line | Data |
---|---|---|
ed10cb95 BW |
1 | Git Wire Protocol, Version 2 |
2 | ============================== | |
3 | ||
4 | This document presents a specification for a version 2 of Git's wire | |
5 | protocol. Protocol v2 will improve upon v1 in the following ways: | |
6 | ||
7 | * Instead of multiple service names, multiple commands will be | |
8 | supported by a single service | |
9 | * Easily extendable as capabilities are moved into their own section | |
10 | of the protocol, no longer being hidden behind a NUL byte and | |
11 | limited by the size of a pkt-line | |
12 | * Separate out other information hidden behind NUL bytes (e.g. agent | |
13 | string as a capability and symrefs can be requested using 'ls-refs') | |
14 | * Reference advertisement will be omitted unless explicitly requested | |
15 | * ls-refs command to explicitly request some refs | |
16 | * Designed with http and stateless-rpc in mind. With clear flush | |
17 | semantics the http remote helper can simply act as a proxy | |
18 | ||
19 | In protocol v2 communication is command oriented. When first contacting a | |
20 | server a list of capabilities will advertised. Some of these capabilities | |
21 | will be commands which a client can request be executed. Once a command | |
22 | has completed, a client can reuse the connection and request that other | |
23 | commands be executed. | |
24 | ||
25 | Packet-Line Framing | |
26 | --------------------- | |
27 | ||
28 | All communication is done using packet-line framing, just as in v1. See | |
29 | `Documentation/technical/pack-protocol.txt` and | |
30 | `Documentation/technical/protocol-common.txt` for more information. | |
31 | ||
32 | In protocol v2 these special packets will have the following semantics: | |
33 | ||
34 | * '0000' Flush Packet (flush-pkt) - indicates the end of a message | |
35 | * '0001' Delimiter Packet (delim-pkt) - separates sections of a message | |
36 | ||
37 | Initial Client Request | |
38 | ------------------------ | |
39 | ||
40 | In general a client can request to speak protocol v2 by sending | |
41 | `version=2` through the respective side-channel for the transport being | |
42 | used which inevitably sets `GIT_PROTOCOL`. More information can be | |
43 | found in `pack-protocol.txt` and `http-protocol.txt`. In all cases the | |
44 | response from the server is the capability advertisement. | |
45 | ||
46 | Git Transport | |
47 | ~~~~~~~~~~~~~~~ | |
48 | ||
49 | When using the git:// transport, you can request to use protocol v2 by | |
50 | sending "version=2" as an extra parameter: | |
51 | ||
52 | 003egit-upload-pack /project.git\0host=myserver.com\0\0version=2\0 | |
53 | ||
54 | SSH and File Transport | |
55 | ~~~~~~~~~~~~~~~~~~~~~~~~ | |
56 | ||
57 | When using either the ssh:// or file:// transport, the GIT_PROTOCOL | |
58 | environment variable must be set explicitly to include "version=2". | |
59 | ||
60 | HTTP Transport | |
61 | ~~~~~~~~~~~~~~~~ | |
62 | ||
63 | When using the http:// or https:// transport a client makes a "smart" | |
64 | info/refs request as described in `http-protocol.txt` and requests that | |
65 | v2 be used by supplying "version=2" in the `Git-Protocol` header. | |
66 | ||
67 | C: Git-Protocol: version=2 | |
68 | C: | |
69 | C: GET $GIT_URL/info/refs?service=git-upload-pack HTTP/1.0 | |
70 | ||
71 | A v2 server would reply: | |
72 | ||
73 | S: 200 OK | |
74 | S: <Some headers> | |
75 | S: ... | |
76 | S: | |
77 | S: 000eversion 2\n | |
78 | S: <capability-advertisement> | |
79 | ||
80 | Subsequent requests are then made directly to the service | |
81 | `$GIT_URL/git-upload-pack`. (This works the same for git-receive-pack). | |
82 | ||
83 | Capability Advertisement | |
84 | -------------------------- | |
85 | ||
86 | A server which decides to communicate (based on a request from a client) | |
87 | using protocol version 2, notifies the client by sending a version string | |
88 | in its initial response followed by an advertisement of its capabilities. | |
89 | Each capability is a key with an optional value. Clients must ignore all | |
90 | unknown keys. Semantics of unknown values are left to the definition of | |
91 | each key. Some capabilities will describe commands which can be requested | |
92 | to be executed by the client. | |
93 | ||
94 | capability-advertisement = protocol-version | |
95 | capability-list | |
96 | flush-pkt | |
97 | ||
98 | protocol-version = PKT-LINE("version 2" LF) | |
99 | capability-list = *capability | |
100 | capability = PKT-LINE(key[=value] LF) | |
101 | ||
102 | key = 1*(ALPHA | DIGIT | "-_") | |
103 | value = 1*(ALPHA | DIGIT | " -_.,?\/{}[]()<>!@#$%^&*+=:;") | |
104 | ||
105 | Command Request | |
106 | ----------------- | |
107 | ||
108 | After receiving the capability advertisement, a client can then issue a | |
109 | request to select the command it wants with any particular capabilities | |
110 | or arguments. There is then an optional section where the client can | |
111 | provide any command specific parameters or queries. Only a single | |
112 | command can be requested at a time. | |
113 | ||
114 | request = empty-request | command-request | |
115 | empty-request = flush-pkt | |
116 | command-request = command | |
117 | capability-list | |
118 | [command-args] | |
119 | flush-pkt | |
120 | command = PKT-LINE("command=" key LF) | |
121 | command-args = delim-pkt | |
122 | *command-specific-arg | |
123 | ||
124 | command-specific-args are packet line framed arguments defined by | |
125 | each individual command. | |
126 | ||
127 | The server will then check to ensure that the client's request is | |
128 | comprised of a valid command as well as valid capabilities which were | |
129 | advertised. If the request is valid the server will then execute the | |
130 | command. A server MUST wait till it has received the client's entire | |
131 | request before issuing a response. The format of the response is | |
132 | determined by the command being executed, but in all cases a flush-pkt | |
133 | indicates the end of the response. | |
134 | ||
135 | When a command has finished, and the client has received the entire | |
136 | response from the server, a client can either request that another | |
137 | command be executed or can terminate the connection. A client may | |
138 | optionally send an empty request consisting of just a flush-pkt to | |
139 | indicate that no more requests will be made. | |
140 | ||
141 | Capabilities | |
142 | -------------- | |
143 | ||
144 | There are two different types of capabilities: normal capabilities, | |
145 | which can be used to to convey information or alter the behavior of a | |
146 | request, and commands, which are the core actions that a client wants to | |
147 | perform (fetch, push, etc). | |
148 | ||
149 | Protocol version 2 is stateless by default. This means that all commands | |
150 | must only last a single round and be stateless from the perspective of the | |
151 | server side, unless the client has requested a capability indicating that | |
152 | state should be maintained by the server. Clients MUST NOT require state | |
153 | management on the server side in order to function correctly. This | |
154 | permits simple round-robin load-balancing on the server side, without | |
155 | needing to worry about state management. | |
156 | ||
157 | agent | |
158 | ~~~~~~~ | |
159 | ||
160 | The server can advertise the `agent` capability with a value `X` (in the | |
161 | form `agent=X`) to notify the client that the server is running version | |
162 | `X`. The client may optionally send its own agent string by including | |
163 | the `agent` capability with a value `Y` (in the form `agent=Y`) in its | |
164 | request to the server (but it MUST NOT do so if the server did not | |
165 | advertise the agent capability). The `X` and `Y` strings may contain any | |
166 | printable ASCII characters except space (i.e., the byte range 32 < x < | |
167 | 127), and are typically of the form "package/version" (e.g., | |
168 | "git/1.8.3.1"). The agent strings are purely informative for statistics | |
169 | and debugging purposes, and MUST NOT be used to programmatically assume | |
170 | the presence or absence of particular features. | |
72d0ea00 BW |
171 | |
172 | ls-refs | |
173 | ~~~~~~~~~ | |
174 | ||
175 | `ls-refs` is the command used to request a reference advertisement in v2. | |
176 | Unlike the current reference advertisement, ls-refs takes in arguments | |
177 | which can be used to limit the refs sent from the server. | |
178 | ||
179 | Additional features not supported in the base command will be advertised | |
180 | as the value of the command in the capability advertisement in the form | |
181 | of a space separated list of features: "<command>=<feature 1> <feature 2>" | |
182 | ||
183 | ls-refs takes in the following arguments: | |
184 | ||
185 | symrefs | |
186 | In addition to the object pointed by it, show the underlying ref | |
187 | pointed by it when showing a symbolic ref. | |
188 | peel | |
189 | Show peeled tags. | |
190 | ref-prefix <prefix> | |
191 | When specified, only references having a prefix matching one of | |
192 | the provided prefixes are displayed. | |
193 | ||
194 | The output of ls-refs is as follows: | |
195 | ||
196 | output = *ref | |
197 | flush-pkt | |
198 | ref = PKT-LINE(obj-id SP refname *(SP ref-attribute) LF) | |
199 | ref-attribute = (symref | peeled) | |
200 | symref = "symref-target:" symref-target | |
201 | peeled = "peeled:" obj-id | |
3145ea95 BW |
202 | |
203 | fetch | |
204 | ~~~~~~~ | |
205 | ||
206 | `fetch` is the command used to fetch a packfile in v2. It can be looked | |
207 | at as a modified version of the v1 fetch where the ref-advertisement is | |
208 | stripped out (since the `ls-refs` command fills that role) and the | |
209 | message format is tweaked to eliminate redundancies and permit easy | |
210 | addition of future extensions. | |
211 | ||
212 | Additional features not supported in the base command will be advertised | |
213 | as the value of the command in the capability advertisement in the form | |
214 | of a space separated list of features: "<command>=<feature 1> <feature 2>" | |
215 | ||
216 | A `fetch` request can take the following arguments: | |
217 | ||
218 | want <oid> | |
219 | Indicates to the server an object which the client wants to | |
220 | retrieve. Wants can be anything and are not limited to | |
221 | advertised objects. | |
222 | ||
223 | have <oid> | |
224 | Indicates to the server an object which the client has locally. | |
225 | This allows the server to make a packfile which only contains | |
226 | the objects that the client needs. Multiple 'have' lines can be | |
227 | supplied. | |
228 | ||
229 | done | |
230 | Indicates to the server that negotiation should terminate (or | |
231 | not even begin if performing a clone) and that the server should | |
232 | use the information supplied in the request to construct the | |
233 | packfile. | |
234 | ||
235 | thin-pack | |
236 | Request that a thin pack be sent, which is a pack with deltas | |
237 | which reference base objects not contained within the pack (but | |
238 | are known to exist at the receiving end). This can reduce the | |
239 | network traffic significantly, but it requires the receiving end | |
240 | to know how to "thicken" these packs by adding the missing bases | |
241 | to the pack. | |
242 | ||
243 | no-progress | |
244 | Request that progress information that would normally be sent on | |
245 | side-band channel 2, during the packfile transfer, should not be | |
246 | sent. However, the side-band channel 3 is still used for error | |
247 | responses. | |
248 | ||
249 | include-tag | |
250 | Request that annotated tags should be sent if the objects they | |
251 | point to are being sent. | |
252 | ||
253 | ofs-delta | |
254 | Indicate that the client understands PACKv2 with delta referring | |
255 | to its base by position in pack rather than by an oid. That is, | |
256 | they can read OBJ_OFS_DELTA (ake type 6) in a packfile. | |
257 | ||
f7e20501 BW |
258 | If the 'shallow' feature is advertised the following arguments can be |
259 | included in the clients request as well as the potential addition of the | |
260 | 'shallow-info' section in the server's response as explained below. | |
261 | ||
685fbd32 BW |
262 | shallow <oid> |
263 | A client must notify the server of all commits for which it only | |
264 | has shallow copies (meaning that it doesn't have the parents of | |
265 | a commit) by supplying a 'shallow <oid>' line for each such | |
266 | object so that the server is aware of the limitations of the | |
267 | client's history. This is so that the server is aware that the | |
268 | client may not have all objects reachable from such commits. | |
269 | ||
270 | deepen <depth> | |
271 | Requests that the fetch/clone should be shallow having a commit | |
272 | depth of <depth> relative to the remote side. | |
273 | ||
274 | deepen-relative | |
275 | Requests that the semantics of the "deepen" command be changed | |
276 | to indicate that the depth requested is relative to the client's | |
277 | current shallow boundary, instead of relative to the requested | |
278 | commits. | |
279 | ||
280 | deepen-since <timestamp> | |
281 | Requests that the shallow clone/fetch should be cut at a | |
282 | specific time, instead of depth. Internally it's equivalent to | |
283 | doing "git rev-list --max-age=<timestamp>". Cannot be used with | |
284 | "deepen". | |
285 | ||
286 | deepen-not <rev> | |
287 | Requests that the shallow clone/fetch should be cut at a | |
288 | specific revision specified by '<rev>', instead of a depth. | |
289 | Internally it's equivalent of doing "git rev-list --not <rev>". | |
290 | Cannot be used with "deepen", but can be used with | |
291 | "deepen-since". | |
292 | ||
ba95710a JT |
293 | If the 'filter' feature is advertised, the following argument can be |
294 | included in the client's request: | |
295 | ||
296 | filter <filter-spec> | |
297 | Request that various objects from the packfile be omitted | |
298 | using one of several filtering techniques. These are intended | |
299 | for use with partial clone and partial fetch operations. See | |
300 | `rev-list` for possible "filter-spec" values. | |
301 | ||
3145ea95 BW |
302 | The response of `fetch` is broken into a number of sections separated by |
303 | delimiter packets (0001), with each section beginning with its section | |
304 | header. | |
305 | ||
306 | output = *section | |
685fbd32 | 307 | section = (acknowledgments | shallow-info | packfile) |
3145ea95 BW |
308 | (flush-pkt | delim-pkt) |
309 | ||
310 | acknowledgments = PKT-LINE("acknowledgments" LF) | |
311 | (nak | *ack) | |
312 | (ready) | |
313 | ready = PKT-LINE("ready" LF) | |
314 | nak = PKT-LINE("NAK" LF) | |
315 | ack = PKT-LINE("ACK" SP obj-id LF) | |
316 | ||
685fbd32 BW |
317 | shallow-info = PKT-LINE("shallow-info" LF) |
318 | *PKT-LINE((shallow | unshallow) LF) | |
319 | shallow = "shallow" SP obj-id | |
320 | unshallow = "unshallow" SP obj-id | |
321 | ||
3145ea95 BW |
322 | packfile = PKT-LINE("packfile" LF) |
323 | *PKT-LINE(%x01-03 *%x00-ff) | |
324 | ||
325 | acknowledgments section | |
326 | * If the client determines that it is finished with negotiations | |
327 | by sending a "done" line, the acknowledgments sections MUST be | |
328 | omitted from the server's response. | |
329 | ||
330 | * Always begins with the section header "acknowledgments" | |
331 | ||
332 | * The server will respond with "NAK" if none of the object ids sent | |
333 | as have lines were common. | |
334 | ||
335 | * The server will respond with "ACK obj-id" for all of the | |
336 | object ids sent as have lines which are common. | |
337 | ||
338 | * A response cannot have both "ACK" lines as well as a "NAK" | |
339 | line. | |
340 | ||
341 | * The server will respond with a "ready" line indicating that | |
342 | the server has found an acceptable common base and is ready to | |
343 | make and send a packfile (which will be found in the packfile | |
344 | section of the same response) | |
345 | ||
346 | * If the server has found a suitable cut point and has decided | |
347 | to send a "ready" line, then the server can decide to (as an | |
348 | optimization) omit any "ACK" lines it would have sent during | |
349 | its response. This is because the server will have already | |
350 | determined the objects it plans to send to the client and no | |
351 | further negotiation is needed. | |
352 | ||
685fbd32 | 353 | shallow-info section |
f7e20501 BW |
354 | * If the client has requested a shallow fetch/clone, a shallow |
355 | client requests a fetch or the server is shallow then the | |
356 | server's response may include a shallow-info section. The | |
357 | shallow-info section will be included if (due to one of the | |
358 | above conditions) the server needs to inform the client of any | |
359 | shallow boundaries or adjustments to the clients already | |
360 | existing shallow boundaries. | |
685fbd32 BW |
361 | |
362 | * Always begins with the section header "shallow-info" | |
363 | ||
364 | * If a positive depth is requested, the server will compute the | |
365 | set of commits which are no deeper than the desired depth. | |
366 | ||
367 | * The server sends a "shallow obj-id" line for each commit whose | |
368 | parents will not be sent in the following packfile. | |
369 | ||
370 | * The server sends an "unshallow obj-id" line for each commit | |
371 | which the client has indicated is shallow, but is no longer | |
372 | shallow as a result of the fetch (due to its parents being | |
373 | sent in the following packfile). | |
374 | ||
375 | * The server MUST NOT send any "unshallow" lines for anything | |
376 | which the client has not indicated was shallow as a part of | |
377 | its request. | |
378 | ||
379 | * This section is only included if a packfile section is also | |
380 | included in the response. | |
381 | ||
3145ea95 BW |
382 | packfile section |
383 | * This section is only included if the client has sent 'want' | |
384 | lines in its request and either requested that no more | |
385 | negotiation be done by sending 'done' or if the server has | |
386 | decided it has found a sufficient cut point to produce a | |
387 | packfile. | |
388 | ||
389 | * Always begins with the section header "packfile" | |
390 | ||
391 | * The transmission of the packfile begins immediately after the | |
392 | section header | |
393 | ||
394 | * The data transfer of the packfile is always multiplexed, using | |
395 | the same semantics of the 'side-band-64k' capability from | |
396 | protocol version 1. This means that each packet, during the | |
397 | packfile data stream, is made up of a leading 4-byte pkt-line | |
398 | length (typical of the pkt-line format), followed by a 1-byte | |
399 | stream code, followed by the actual data. | |
400 | ||
401 | The stream code can be one of: | |
402 | 1 - pack data | |
403 | 2 - progress messages | |
404 | 3 - fatal error message just before stream aborts | |
ecc3e534 BW |
405 | |
406 | server-option | |
407 | ~~~~~~~~~~~~~~~ | |
408 | ||
409 | If advertised, indicates that any number of server specific options can be | |
410 | included in a request. This is done by sending each option as a | |
411 | "server-option=<option>" capability line in the capability-list section of | |
412 | a request. | |
413 | ||
414 | The provided options must not contain a NUL or LF character. |