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b31222cf SC |
1 | Packfile transfer protocols |
2 | =========================== | |
3 | ||
055c7e9f | 4 | Git supports transferring data in packfiles over the ssh://, git://, http:// and |
b31222cf SC |
5 | file:// transports. There exist two sets of protocols, one for pushing |
6 | data from a client to a server and another for fetching data from a | |
055c7e9f SB |
7 | server to a client. The three transports (ssh, git, file) use the same |
8 | protocol to transfer data. http is documented in http-protocol.txt. | |
b31222cf SC |
9 | |
10 | The processes invoked in the canonical Git implementation are 'upload-pack' | |
11 | on the server side and 'fetch-pack' on the client side for fetching data; | |
12 | then 'receive-pack' on the server and 'send-pack' on the client for pushing | |
13 | data. The protocol functions to have a server tell a client what is | |
14 | currently on the server, then for the two to negotiate the smallest amount | |
15 | of data to send in order to fully update one or the other. | |
16 | ||
1c9b659d JK |
17 | pkt-line Format |
18 | --------------- | |
19 | ||
20 | The descriptions below build on the pkt-line format described in | |
21 | protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless | |
22 | otherwise noted the usual pkt-line LF rules apply: the sender SHOULD | |
23 | include a LF, but the receiver MUST NOT complain if it is not present. | |
24 | ||
2d103c31 MS |
25 | An error packet is a special pkt-line that contains an error string. |
26 | ||
27 | ---- | |
28 | error-line = PKT-LINE("ERR" SP explanation-text) | |
29 | ---- | |
30 | ||
31 | Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY | |
32 | be sent. Once this packet is sent by a client or a server, the data transfer | |
33 | process defined in this protocol is terminated. | |
34 | ||
b31222cf SC |
35 | Transports |
36 | ---------- | |
37 | There are three transports over which the packfile protocol is | |
38 | initiated. The Git transport is a simple, unauthenticated server that | |
39 | takes the command (almost always 'upload-pack', though Git | |
40 | servers can be configured to be globally writable, in which 'receive- | |
41 | pack' initiation is also allowed) with which the client wishes to | |
42 | communicate and executes it and connects it to the requesting | |
43 | process. | |
44 | ||
45 | In the SSH transport, the client just runs the 'upload-pack' | |
46 | or 'receive-pack' process on the server over the SSH protocol and then | |
47 | communicates with that invoked process over the SSH connection. | |
48 | ||
49 | The file:// transport runs the 'upload-pack' or 'receive-pack' | |
50 | process locally and communicates with it over a pipe. | |
51 | ||
6464679d JT |
52 | Extra Parameters |
53 | ---------------- | |
54 | ||
55 | The protocol provides a mechanism in which clients can send additional | |
56 | information in its first message to the server. These are called "Extra | |
57 | Parameters", and are supported by the Git, SSH, and HTTP protocols. | |
58 | ||
59 | Each Extra Parameter takes the form of `<key>=<value>` or `<key>`. | |
60 | ||
61 | Servers that receive any such Extra Parameters MUST ignore all | |
62 | unrecognized keys. Currently, the only Extra Parameter recognized is | |
f351b0ab BW |
63 | "version" with a value of '1' or '2'. See protocol-v2.txt for more |
64 | information on protocol version 2. | |
6464679d | 65 | |
b31222cf SC |
66 | Git Transport |
67 | ------------- | |
68 | ||
69 | The Git transport starts off by sending the command and repository | |
70 | on the wire using the pkt-line format, followed by a NUL byte and a | |
8e50175d | 71 | hostname parameter, terminated by a NUL byte. |
b31222cf | 72 | |
6464679d JT |
73 | 0033git-upload-pack /project.git\0host=myserver.com\0 |
74 | ||
75 | The transport may send Extra Parameters by adding an additional NUL | |
76 | byte, and then adding one or more NUL-terminated strings: | |
77 | ||
78 | 003egit-upload-pack /project.git\0host=myserver.com\0\0version=1\0 | |
b31222cf SC |
79 | |
80 | -- | |
6464679d JT |
81 | git-proto-request = request-command SP pathname NUL |
82 | [ host-parameter NUL ] [ NUL extra-parameters ] | |
b31222cf SC |
83 | request-command = "git-upload-pack" / "git-receive-pack" / |
84 | "git-upload-archive" ; case sensitive | |
85 | pathname = *( %x01-ff ) ; exclude NUL | |
86 | host-parameter = "host=" hostname [ ":" port ] | |
6464679d JT |
87 | extra-parameters = 1*extra-parameter |
88 | extra-parameter = 1*( %x01-ff ) NUL | |
b31222cf SC |
89 | -- |
90 | ||
6464679d | 91 | host-parameter is used for the |
b31222cf SC |
92 | git-daemon name based virtual hosting. See --interpolated-path |
93 | option to git daemon, with the %H/%CH format characters. | |
94 | ||
95 | Basically what the Git client is doing to connect to an 'upload-pack' | |
96 | process on the server side over the Git protocol is this: | |
97 | ||
98 | $ echo -e -n \ | |
99 | "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" | | |
100 | nc -v example.com 9418 | |
101 | ||
102 | ||
103 | SSH Transport | |
104 | ------------- | |
105 | ||
106 | Initiating the upload-pack or receive-pack processes over SSH is | |
107 | executing the binary on the server via SSH remote execution. | |
108 | It is basically equivalent to running this: | |
109 | ||
110 | $ ssh git.example.com "git-upload-pack '/project.git'" | |
111 | ||
112 | For a server to support Git pushing and pulling for a given user over | |
113 | SSH, that user needs to be able to execute one or both of those | |
114 | commands via the SSH shell that they are provided on login. On some | |
115 | systems, that shell access is limited to only being able to run those | |
116 | two commands, or even just one of them. | |
117 | ||
118 | In an ssh:// format URI, it's absolute in the URI, so the '/' after | |
119 | the host name (or port number) is sent as an argument, which is then | |
120 | read by the remote git-upload-pack exactly as is, so it's effectively | |
121 | an absolute path in the remote filesystem. | |
122 | ||
123 | git clone ssh://user@example.com/project.git | |
124 | | | |
125 | v | |
126 | ssh user@example.com "git-upload-pack '/project.git'" | |
127 | ||
128 | In a "user@host:path" format URI, its relative to the user's home | |
129 | directory, because the Git client will run: | |
130 | ||
131 | git clone user@example.com:project.git | |
132 | | | |
133 | v | |
134 | ssh user@example.com "git-upload-pack 'project.git'" | |
135 | ||
136 | The exception is if a '~' is used, in which case | |
137 | we execute it without the leading '/'. | |
138 | ||
139 | ssh://user@example.com/~alice/project.git, | |
140 | | | |
141 | v | |
142 | ssh user@example.com "git-upload-pack '~alice/project.git'" | |
143 | ||
6464679d JT |
144 | Depending on the value of the `protocol.version` configuration variable, |
145 | Git may attempt to send Extra Parameters as a colon-separated string in | |
146 | the GIT_PROTOCOL environment variable. This is done only if | |
147 | the `ssh.variant` configuration variable indicates that the ssh command | |
148 | supports passing environment variables as an argument. | |
149 | ||
b31222cf SC |
150 | A few things to remember here: |
151 | ||
152 | - The "command name" is spelled with dash (e.g. git-upload-pack), but | |
153 | this can be overridden by the client; | |
154 | ||
155 | - The repository path is always quoted with single quotes. | |
156 | ||
157 | Fetching Data From a Server | |
5316c8e9 | 158 | --------------------------- |
b31222cf SC |
159 | |
160 | When one Git repository wants to get data that a second repository | |
161 | has, the first can 'fetch' from the second. This operation determines | |
162 | what data the server has that the client does not then streams that | |
163 | data down to the client in packfile format. | |
164 | ||
165 | ||
166 | Reference Discovery | |
167 | ------------------- | |
168 | ||
169 | When the client initially connects the server will immediately respond | |
6464679d JT |
170 | with a version number (if "version=1" is sent as an Extra Parameter), |
171 | and a listing of each reference it has (all branches and tags) along | |
b31222cf SC |
172 | with the object name that each reference currently points to. |
173 | ||
6464679d | 174 | $ echo -e -n "0044git-upload-pack /schacon/gitbook.git\0host=example.com\0\0version=1\0" | |
b31222cf | 175 | nc -v example.com 9418 |
6464679d | 176 | 000aversion 1 |
5316c8e9 TA |
177 | 00887217a7c7e582c46cec22a130adf4b9d7d950fba0 HEAD\0multi_ack thin-pack |
178 | side-band side-band-64k ofs-delta shallow no-progress include-tag | |
b31222cf SC |
179 | 00441d3fcd5ced445d1abc402225c0b8a1299641f497 refs/heads/integration |
180 | 003f7217a7c7e582c46cec22a130adf4b9d7d950fba0 refs/heads/master | |
181 | 003cb88d2441cac0977faf98efc80305012112238d9d refs/tags/v0.9 | |
182 | 003c525128480b96c89e6418b1e40909bf6c5b2d580f refs/tags/v1.0 | |
183 | 003fe92df48743b7bc7d26bcaabfddde0a1e20cae47c refs/tags/v1.0^{} | |
184 | 0000 | |
185 | ||
b31222cf SC |
186 | The returned response is a pkt-line stream describing each ref and |
187 | its current value. The stream MUST be sorted by name according to | |
188 | the C locale ordering. | |
189 | ||
190 | If HEAD is a valid ref, HEAD MUST appear as the first advertised | |
191 | ref. If HEAD is not a valid ref, HEAD MUST NOT appear in the | |
192 | advertisement list at all, but other refs may still appear. | |
193 | ||
194 | The stream MUST include capability declarations behind a NUL on the | |
195 | first ref. The peeled value of a ref (that is "ref^{}") MUST be | |
196 | immediately after the ref itself, if presented. A conforming server | |
6a5d0b0a | 197 | MUST peel the ref if it's an annotated tag. |
b31222cf SC |
198 | |
199 | ---- | |
6464679d JT |
200 | advertised-refs = *1("version 1") |
201 | (no-refs / list-of-refs) | |
ad491366 | 202 | *shallow |
b31222cf SC |
203 | flush-pkt |
204 | ||
205 | no-refs = PKT-LINE(zero-id SP "capabilities^{}" | |
1c9b659d | 206 | NUL capability-list) |
b31222cf SC |
207 | |
208 | list-of-refs = first-ref *other-ref | |
209 | first-ref = PKT-LINE(obj-id SP refname | |
1c9b659d | 210 | NUL capability-list) |
b31222cf SC |
211 | |
212 | other-ref = PKT-LINE(other-tip / other-peeled) | |
1c9b659d JK |
213 | other-tip = obj-id SP refname |
214 | other-peeled = obj-id SP refname "^{}" | |
b31222cf | 215 | |
ad491366 NTND |
216 | shallow = PKT-LINE("shallow" SP obj-id) |
217 | ||
b31222cf SC |
218 | capability-list = capability *(SP capability) |
219 | capability = 1*(LC_ALPHA / DIGIT / "-" / "_") | |
220 | LC_ALPHA = %x61-7A | |
221 | ---- | |
222 | ||
223 | Server and client MUST use lowercase for obj-id, both MUST treat obj-id | |
224 | as case-insensitive. | |
225 | ||
226 | See protocol-capabilities.txt for a list of allowed server capabilities | |
227 | and descriptions. | |
228 | ||
229 | Packfile Negotiation | |
230 | -------------------- | |
a1e90b23 AN |
231 | After reference and capabilities discovery, the client can decide to |
232 | terminate the connection by sending a flush-pkt, telling the server it can | |
233 | now gracefully terminate, and disconnect, when it does not need any pack | |
234 | data. This can happen with the ls-remote command, and also can happen when | |
7560f547 | 235 | the client already is up to date. |
a1e90b23 AN |
236 | |
237 | Otherwise, it enters the negotiation phase, where the client and | |
238 | server determine what the minimal packfile necessary for transport is, | |
4a1c2695 AN |
239 | by telling the server what objects it wants, its shallow objects |
240 | (if any), and the maximum commit depth it wants (if any). The client | |
241 | will also send a list of the capabilities it wants to be in effect, | |
242 | out of what the server said it could do with the first 'want' line. | |
b31222cf SC |
243 | |
244 | ---- | |
245 | upload-request = want-list | |
4a1c2695 AN |
246 | *shallow-line |
247 | *1depth-request | |
10ac85c7 | 248 | [filter-request] |
4a1c2695 | 249 | flush-pkt |
b31222cf SC |
250 | |
251 | want-list = first-want | |
252 | *additional-want | |
4a1c2695 | 253 | |
e543b3f6 | 254 | shallow-line = PKT-LINE("shallow" SP obj-id) |
4a1c2695 | 255 | |
569e554b | 256 | depth-request = PKT-LINE("deepen" SP depth) / |
269a7a83 NTND |
257 | PKT-LINE("deepen-since" SP timestamp) / |
258 | PKT-LINE("deepen-not" SP ref) | |
b31222cf | 259 | |
1c9b659d JK |
260 | first-want = PKT-LINE("want" SP obj-id SP capability-list) |
261 | additional-want = PKT-LINE("want" SP obj-id) | |
b31222cf | 262 | |
4a1c2695 | 263 | depth = 1*DIGIT |
10ac85c7 JH |
264 | |
265 | filter-request = PKT-LINE("filter" SP filter-spec) | |
b31222cf SC |
266 | ---- |
267 | ||
268 | Clients MUST send all the obj-ids it wants from the reference | |
269 | discovery phase as 'want' lines. Clients MUST send at least one | |
270 | 'want' command in the request body. Clients MUST NOT mention an | |
271 | obj-id in a 'want' command which did not appear in the response | |
272 | obtained through ref discovery. | |
273 | ||
4a1c2695 AN |
274 | The client MUST write all obj-ids which it only has shallow copies |
275 | of (meaning that it does not have the parents of a commit) as | |
276 | 'shallow' lines so that the server is aware of the limitations of | |
af04fa2a | 277 | the client's history. |
4a1c2695 AN |
278 | |
279 | The client now sends the maximum commit history depth it wants for | |
280 | this transaction, which is the number of commits it wants from the | |
281 | tip of the history, if any, as a 'deepen' line. A depth of 0 is the | |
282 | same as not making a depth request. The client does not want to receive | |
a58088ab JL |
283 | any commits beyond this depth, nor does it want objects needed only to |
284 | complete those commits. Commits whose parents are not received as a | |
285 | result are defined as shallow and marked as such in the server. This | |
286 | information is sent back to the client in the next step. | |
4a1c2695 | 287 | |
10ac85c7 JH |
288 | The client can optionally request that pack-objects omit various |
289 | objects from the packfile using one of several filtering techniques. | |
290 | These are intended for use with partial clone and partial fetch | |
a0c9016a JT |
291 | operations. An object that does not meet a filter-spec value is |
292 | omitted unless explicitly requested in a 'want' line. See `rev-list` | |
293 | for possible filter-spec values. | |
10ac85c7 | 294 | |
4a1c2695 AN |
295 | Once all the 'want's and 'shallow's (and optional 'deepen') are |
296 | transferred, clients MUST send a flush-pkt, to tell the server side | |
297 | that it is done sending the list. | |
298 | ||
299 | Otherwise, if the client sent a positive depth request, the server | |
300 | will determine which commits will and will not be shallow and | |
301 | send this information to the client. If the client did not request | |
302 | a positive depth, this step is skipped. | |
b31222cf | 303 | |
4a1c2695 AN |
304 | ---- |
305 | shallow-update = *shallow-line | |
306 | *unshallow-line | |
307 | flush-pkt | |
b31222cf | 308 | |
4a1c2695 AN |
309 | shallow-line = PKT-LINE("shallow" SP obj-id) |
310 | ||
311 | unshallow-line = PKT-LINE("unshallow" SP obj-id) | |
312 | ---- | |
313 | ||
314 | If the client has requested a positive depth, the server will compute | |
01f7d7f1 PO |
315 | the set of commits which are no deeper than the desired depth. The set |
316 | of commits start at the client's wants. | |
317 | ||
318 | The server writes 'shallow' lines for each | |
4a1c2695 AN |
319 | commit whose parents will not be sent as a result. The server writes |
320 | an 'unshallow' line for each commit which the client has indicated is | |
321 | shallow, but is no longer shallow at the currently requested depth | |
322 | (that is, its parents will now be sent). The server MUST NOT mark | |
323 | as unshallow anything which the client has not indicated was shallow. | |
b31222cf SC |
324 | |
325 | Now the client will send a list of the obj-ids it has using 'have' | |
4a1c2695 AN |
326 | lines, so the server can make a packfile that only contains the objects |
327 | that the client needs. In multi_ack mode, the canonical implementation | |
328 | will send up to 32 of these at a time, then will send a flush-pkt. The | |
329 | canonical implementation will skip ahead and send the next 32 immediately, | |
330 | so that there is always a block of 32 "in-flight on the wire" at a time. | |
331 | ||
332 | ---- | |
333 | upload-haves = have-list | |
334 | compute-end | |
335 | ||
336 | have-list = *have-line | |
1c9b659d | 337 | have-line = PKT-LINE("have" SP obj-id) |
4a1c2695 AN |
338 | compute-end = flush-pkt / PKT-LINE("done") |
339 | ---- | |
b31222cf SC |
340 | |
341 | If the server reads 'have' lines, it then will respond by ACKing any | |
342 | of the obj-ids the client said it had that the server also has. The | |
343 | server will ACK obj-ids differently depending on which ack mode is | |
344 | chosen by the client. | |
345 | ||
346 | In multi_ack mode: | |
347 | ||
348 | * the server will respond with 'ACK obj-id continue' for any common | |
349 | commits. | |
350 | ||
351 | * once the server has found an acceptable common base commit and is | |
352 | ready to make a packfile, it will blindly ACK all 'have' obj-ids | |
353 | back to the client. | |
354 | ||
280abfd4 | 355 | * the server will then send a 'NAK' and then wait for another response |
b31222cf SC |
356 | from the client - either a 'done' or another list of 'have' lines. |
357 | ||
358 | In multi_ack_detailed mode: | |
359 | ||
360 | * the server will differentiate the ACKs where it is signaling | |
361 | that it is ready to send data with 'ACK obj-id ready' lines, and | |
362 | signals the identified common commits with 'ACK obj-id common' lines. | |
363 | ||
364 | Without either multi_ack or multi_ack_detailed: | |
365 | ||
366 | * upload-pack sends "ACK obj-id" on the first common object it finds. | |
367 | After that it says nothing until the client gives it a "done". | |
368 | ||
369 | * upload-pack sends "NAK" on a flush-pkt if no common object | |
370 | has been found yet. If one has been found, and thus an ACK | |
6a5d0b0a | 371 | was already sent, it's silent on the flush-pkt. |
b31222cf SC |
372 | |
373 | After the client has gotten enough ACK responses that it can determine | |
374 | that the server has enough information to send an efficient packfile | |
375 | (in the canonical implementation, this is determined when it has received | |
376 | enough ACKs that it can color everything left in the --date-order queue | |
377 | as common with the server, or the --date-order queue is empty), or the | |
378 | client determines that it wants to give up (in the canonical implementation, | |
379 | this is determined when the client sends 256 'have' lines without getting | |
380 | any of them ACKed by the server - meaning there is nothing in common and | |
6a5d0b0a | 381 | the server should just send all of its objects), then the client will send |
b31222cf | 382 | a 'done' command. The 'done' command signals to the server that the client |
6a5d0b0a | 383 | is ready to receive its packfile data. |
b31222cf SC |
384 | |
385 | However, the 256 limit *only* turns on in the canonical client | |
386 | implementation if we have received at least one "ACK %s continue" | |
387 | during a prior round. This helps to ensure that at least one common | |
388 | ancestor is found before we give up entirely. | |
389 | ||
390 | Once the 'done' line is read from the client, the server will either | |
32752e96 NTND |
391 | send a final 'ACK obj-id' or it will send a 'NAK'. 'obj-id' is the object |
392 | name of the last commit determined to be common. The server only sends | |
b31222cf SC |
393 | ACK after 'done' if there is at least one common base and multi_ack or |
394 | multi_ack_detailed is enabled. The server always sends NAK after 'done' | |
395 | if there is no common base found. | |
396 | ||
8e2c7bef JT |
397 | Instead of 'ACK' or 'NAK', the server may send an error message (for |
398 | example, if it does not recognize an object in a 'want' line received | |
399 | from the client). | |
400 | ||
6a5d0b0a | 401 | Then the server will start sending its packfile data. |
b31222cf SC |
402 | |
403 | ---- | |
2d103c31 | 404 | server-response = *ack_multi ack / nak |
1c9b659d | 405 | ack_multi = PKT-LINE("ACK" SP obj-id ack_status) |
b31222cf | 406 | ack_status = "continue" / "common" / "ready" |
1c9b659d JK |
407 | ack = PKT-LINE("ACK" SP obj-id) |
408 | nak = PKT-LINE("NAK") | |
b31222cf SC |
409 | ---- |
410 | ||
411 | A simple clone may look like this (with no 'have' lines): | |
412 | ||
413 | ---- | |
79135e4c | 414 | C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \ |
b31222cf SC |
415 | side-band-64k ofs-delta\n |
416 | C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n | |
417 | C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n | |
418 | C: 0032want 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n | |
419 | C: 0032want 74730d410fcb6603ace96f1dc55ea6196122532d\n | |
420 | C: 0000 | |
421 | C: 0009done\n | |
422 | ||
423 | S: 0008NAK\n | |
424 | S: [PACKFILE] | |
425 | ---- | |
426 | ||
427 | An incremental update (fetch) response might look like this: | |
428 | ||
429 | ---- | |
79135e4c | 430 | C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \ |
b31222cf SC |
431 | side-band-64k ofs-delta\n |
432 | C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n | |
433 | C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n | |
434 | C: 0000 | |
435 | C: 0032have 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n | |
436 | C: [30 more have lines] | |
437 | C: 0032have 74730d410fcb6603ace96f1dc55ea6196122532d\n | |
438 | C: 0000 | |
439 | ||
440 | S: 003aACK 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01 continue\n | |
441 | S: 003aACK 74730d410fcb6603ace96f1dc55ea6196122532d continue\n | |
442 | S: 0008NAK\n | |
443 | ||
444 | C: 0009done\n | |
445 | ||
c8a97906 | 446 | S: 0031ACK 74730d410fcb6603ace96f1dc55ea6196122532d\n |
b31222cf SC |
447 | S: [PACKFILE] |
448 | ---- | |
449 | ||
450 | ||
451 | Packfile Data | |
452 | ------------- | |
453 | ||
454 | Now that the client and server have finished negotiation about what | |
455 | the minimal amount of data that needs to be sent to the client is, the server | |
456 | will construct and send the required data in packfile format. | |
457 | ||
458 | See pack-format.txt for what the packfile itself actually looks like. | |
459 | ||
460 | If 'side-band' or 'side-band-64k' capabilities have been specified by | |
461 | the client, the server will send the packfile data multiplexed. | |
462 | ||
463 | Each packet starting with the packet-line length of the amount of data | |
464 | that follows, followed by a single byte specifying the sideband the | |
465 | following data is coming in on. | |
466 | ||
467 | In 'side-band' mode, it will send up to 999 data bytes plus 1 control | |
468 | code, for a total of up to 1000 bytes in a pkt-line. In 'side-band-64k' | |
469 | mode it will send up to 65519 data bytes plus 1 control code, for a | |
470 | total of up to 65520 bytes in a pkt-line. | |
471 | ||
472 | The sideband byte will be a '1', '2' or a '3'. Sideband '1' will contain | |
473 | packfile data, sideband '2' will be used for progress information that the | |
474 | client will generally print to stderr and sideband '3' is used for error | |
475 | information. | |
476 | ||
477 | If no 'side-band' capability was specified, the server will stream the | |
478 | entire packfile without multiplexing. | |
479 | ||
480 | ||
481 | Pushing Data To a Server | |
5316c8e9 | 482 | ------------------------ |
b31222cf SC |
483 | |
484 | Pushing data to a server will invoke the 'receive-pack' process on the | |
485 | server, which will allow the client to tell it which references it should | |
486 | update and then send all the data the server will need for those new | |
487 | references to be complete. Once all the data is received and validated, | |
488 | the server will then update its references to what the client specified. | |
489 | ||
490 | Authentication | |
491 | -------------- | |
492 | ||
493 | The protocol itself contains no authentication mechanisms. That is to be | |
494 | handled by the transport, such as SSH, before the 'receive-pack' process is | |
495 | invoked. If 'receive-pack' is configured over the Git transport, those | |
496 | repositories will be writable by anyone who can access that port (9418) as | |
497 | that transport is unauthenticated. | |
498 | ||
499 | Reference Discovery | |
500 | ------------------- | |
501 | ||
502 | The reference discovery phase is done nearly the same way as it is in the | |
503 | fetching protocol. Each reference obj-id and name on the server is sent | |
504 | in packet-line format to the client, followed by a flush-pkt. The only | |
505 | real difference is that the capability listing is different - the only | |
c714e45f SB |
506 | possible values are 'report-status', 'delete-refs', 'ofs-delta' and |
507 | 'push-options'. | |
b31222cf SC |
508 | |
509 | Reference Update Request and Packfile Transfer | |
510 | ---------------------------------------------- | |
511 | ||
512 | Once the client knows what references the server is at, it can send a | |
513 | list of reference update requests. For each reference on the server | |
514 | that it wants to update, it sends a line listing the obj-id currently on | |
515 | the server, the obj-id the client would like to update it to and the name | |
516 | of the reference. | |
517 | ||
cbaf82cc | 518 | This list is followed by a flush-pkt. |
b31222cf SC |
519 | |
520 | ---- | |
cbaf82cc | 521 | update-requests = *shallow ( command-list | push-cert ) |
5dbd7676 | 522 | |
1c9b659d | 523 | shallow = PKT-LINE("shallow" SP obj-id) |
b31222cf | 524 | |
1c9b659d JK |
525 | command-list = PKT-LINE(command NUL capability-list) |
526 | *PKT-LINE(command) | |
b31222cf SC |
527 | flush-pkt |
528 | ||
529 | command = create / delete / update | |
530 | create = zero-id SP new-id SP name | |
531 | delete = old-id SP zero-id SP name | |
532 | update = old-id SP new-id SP name | |
533 | ||
534 | old-id = obj-id | |
535 | new-id = obj-id | |
536 | ||
4adf569d JH |
537 | push-cert = PKT-LINE("push-cert" NUL capability-list LF) |
538 | PKT-LINE("certificate version 0.1" LF) | |
539 | PKT-LINE("pusher" SP ident LF) | |
9be89160 | 540 | PKT-LINE("pushee" SP url LF) |
b89363e4 | 541 | PKT-LINE("nonce" SP nonce LF) |
cbaf82cc | 542 | *PKT-LINE("push-option" SP push-option LF) |
4adf569d JH |
543 | PKT-LINE(LF) |
544 | *PKT-LINE(command LF) | |
545 | *PKT-LINE(gpg-signature-lines LF) | |
546 | PKT-LINE("push-cert-end" LF) | |
547 | ||
cbaf82cc JT |
548 | push-option = 1*( VCHAR | SP ) |
549 | ---- | |
550 | ||
551 | If the server has advertised the 'push-options' capability and the client has | |
552 | specified 'push-options' as part of the capability list above, the client then | |
553 | sends its push options followed by a flush-pkt. | |
554 | ||
555 | ---- | |
556 | push-options = *PKT-LINE(push-option) flush-pkt | |
557 | ---- | |
558 | ||
559 | For backwards compatibility with older Git servers, if the client sends a push | |
560 | cert and push options, it MUST send its push options both embedded within the | |
561 | push cert and after the push cert. (Note that the push options within the cert | |
562 | are prefixed, but the push options after the cert are not.) Both these lists | |
563 | MUST be the same, modulo the prefix. | |
564 | ||
565 | After that the packfile that | |
566 | should contain all the objects that the server will need to complete the new | |
567 | references will be sent. | |
568 | ||
569 | ---- | |
570 | packfile = "PACK" 28*(OCTET) | |
b31222cf SC |
571 | ---- |
572 | ||
573 | If the receiving end does not support delete-refs, the sending end MUST | |
574 | NOT ask for delete command. | |
575 | ||
4adf569d JH |
576 | If the receiving end does not support push-cert, the sending end |
577 | MUST NOT send a push-cert command. When a push-cert command is | |
578 | sent, command-list MUST NOT be sent; the commands recorded in the | |
579 | push certificate is used instead. | |
580 | ||
3890dae9 | 581 | The packfile MUST NOT be sent if the only command used is 'delete'. |
b31222cf | 582 | |
3890dae9 | 583 | A packfile MUST be sent if either create or update command is used, |
b31222cf | 584 | even if the server already has all the necessary objects. In this |
3890dae9 | 585 | case the client MUST send an empty packfile. The only time this |
b31222cf SC |
586 | is likely to happen is if the client is creating |
587 | a new branch or a tag that points to an existing obj-id. | |
588 | ||
589 | The server will receive the packfile, unpack it, then validate each | |
590 | reference that is being updated that it hasn't changed while the request | |
591 | was being processed (the obj-id is still the same as the old-id), and | |
592 | it will run any update hooks to make sure that the update is acceptable. | |
593 | If all of that is fine, the server will then update the references. | |
594 | ||
4adf569d JH |
595 | Push Certificate |
596 | ---------------- | |
597 | ||
598 | A push certificate begins with a set of header lines. After the | |
599 | header and an empty line, the protocol commands follow, one per | |
832c0e5e | 600 | line. Note that the trailing LF in push-cert PKT-LINEs is _not_ |
1c9b659d | 601 | optional; it must be present. |
4adf569d JH |
602 | |
603 | Currently, the following header fields are defined: | |
604 | ||
605 | `pusher` ident:: | |
606 | Identify the GPG key in "Human Readable Name <email@address>" | |
607 | format. | |
608 | ||
9be89160 JH |
609 | `pushee` url:: |
610 | The repository URL (anonymized, if the URL contains | |
611 | authentication material) the user who ran `git push` | |
612 | intended to push into. | |
613 | ||
b89363e4 JH |
614 | `nonce` nonce:: |
615 | The 'nonce' string the receiving repository asked the | |
616 | pushing user to include in the certificate, to prevent | |
617 | replay attacks. | |
618 | ||
4adf569d JH |
619 | The GPG signature lines are a detached signature for the contents |
620 | recorded in the push certificate before the signature block begins. | |
621 | The detached signature is used to certify that the commands were | |
622 | given by the pusher, who must be the signer. | |
623 | ||
b31222cf SC |
624 | Report Status |
625 | ------------- | |
626 | ||
627 | After receiving the pack data from the sender, the receiver sends a | |
628 | report if 'report-status' capability is in effect. | |
629 | It is a short listing of what happened in that update. It will first | |
630 | list the status of the packfile unpacking as either 'unpack ok' or | |
631 | 'unpack [error]'. Then it will list the status for each of the references | |
632 | that it tried to update. Each line is either 'ok [refname]' if the | |
633 | update was successful, or 'ng [refname] [error]' if the update was not. | |
634 | ||
635 | ---- | |
636 | report-status = unpack-status | |
637 | 1*(command-status) | |
638 | flush-pkt | |
639 | ||
1c9b659d | 640 | unpack-status = PKT-LINE("unpack" SP unpack-result) |
b31222cf SC |
641 | unpack-result = "ok" / error-msg |
642 | ||
643 | command-status = command-ok / command-fail | |
1c9b659d JK |
644 | command-ok = PKT-LINE("ok" SP refname) |
645 | command-fail = PKT-LINE("ng" SP refname SP error-msg) | |
b31222cf SC |
646 | |
647 | error-msg = 1*(OCTECT) ; where not "ok" | |
648 | ---- | |
649 | ||
650 | Updates can be unsuccessful for a number of reasons. The reference can have | |
651 | changed since the reference discovery phase was originally sent, meaning | |
652 | someone pushed in the meantime. The reference being pushed could be a | |
653 | non-fast-forward reference and the update hooks or configuration could be | |
654 | set to not allow that, etc. Also, some references can be updated while others | |
655 | can be rejected. | |
656 | ||
657 | An example client/server communication might look like this: | |
658 | ||
659 | ---- | |
74cc547b | 660 | S: 006274730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n |
b31222cf SC |
661 | S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n |
662 | S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n | |
74cc547b | 663 | S: 003d74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n |
b31222cf SC |
664 | S: 0000 |
665 | ||
74cc547b MH |
666 | C: 00677d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n |
667 | C: 006874730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n | |
b31222cf SC |
668 | C: 0000 |
669 | C: [PACKDATA] | |
670 | ||
c8a97906 TRC |
671 | S: 000eunpack ok\n |
672 | S: 0018ok refs/heads/debug\n | |
673 | S: 002ang refs/heads/master non-fast-forward\n | |
b31222cf | 674 | ---- |