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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 | ||
b31222cf SC |
25 | Transports |
26 | ---------- | |
27 | There are three transports over which the packfile protocol is | |
28 | initiated. The Git transport is a simple, unauthenticated server that | |
29 | takes the command (almost always 'upload-pack', though Git | |
30 | servers can be configured to be globally writable, in which 'receive- | |
31 | pack' initiation is also allowed) with which the client wishes to | |
32 | communicate and executes it and connects it to the requesting | |
33 | process. | |
34 | ||
35 | In the SSH transport, the client just runs the 'upload-pack' | |
36 | or 'receive-pack' process on the server over the SSH protocol and then | |
37 | communicates with that invoked process over the SSH connection. | |
38 | ||
39 | The file:// transport runs the 'upload-pack' or 'receive-pack' | |
40 | process locally and communicates with it over a pipe. | |
41 | ||
6464679d JT |
42 | Extra Parameters |
43 | ---------------- | |
44 | ||
45 | The protocol provides a mechanism in which clients can send additional | |
46 | information in its first message to the server. These are called "Extra | |
47 | Parameters", and are supported by the Git, SSH, and HTTP protocols. | |
48 | ||
49 | Each Extra Parameter takes the form of `<key>=<value>` or `<key>`. | |
50 | ||
51 | Servers that receive any such Extra Parameters MUST ignore all | |
52 | unrecognized keys. Currently, the only Extra Parameter recognized is | |
53 | "version=1". | |
54 | ||
b31222cf SC |
55 | Git Transport |
56 | ------------- | |
57 | ||
58 | The Git transport starts off by sending the command and repository | |
59 | on the wire using the pkt-line format, followed by a NUL byte and a | |
8e50175d | 60 | hostname parameter, terminated by a NUL byte. |
b31222cf | 61 | |
6464679d JT |
62 | 0033git-upload-pack /project.git\0host=myserver.com\0 |
63 | ||
64 | The transport may send Extra Parameters by adding an additional NUL | |
65 | byte, and then adding one or more NUL-terminated strings: | |
66 | ||
67 | 003egit-upload-pack /project.git\0host=myserver.com\0\0version=1\0 | |
b31222cf SC |
68 | |
69 | -- | |
6464679d JT |
70 | git-proto-request = request-command SP pathname NUL |
71 | [ host-parameter NUL ] [ NUL extra-parameters ] | |
b31222cf SC |
72 | request-command = "git-upload-pack" / "git-receive-pack" / |
73 | "git-upload-archive" ; case sensitive | |
74 | pathname = *( %x01-ff ) ; exclude NUL | |
75 | host-parameter = "host=" hostname [ ":" port ] | |
6464679d JT |
76 | extra-parameters = 1*extra-parameter |
77 | extra-parameter = 1*( %x01-ff ) NUL | |
b31222cf SC |
78 | -- |
79 | ||
6464679d | 80 | host-parameter is used for the |
b31222cf SC |
81 | git-daemon name based virtual hosting. See --interpolated-path |
82 | option to git daemon, with the %H/%CH format characters. | |
83 | ||
84 | Basically what the Git client is doing to connect to an 'upload-pack' | |
85 | process on the server side over the Git protocol is this: | |
86 | ||
87 | $ echo -e -n \ | |
88 | "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" | | |
89 | nc -v example.com 9418 | |
90 | ||
d78e5aec NTND |
91 | If the server refuses the request for some reasons, it could abort |
92 | gracefully with an error message. | |
93 | ||
94 | ---- | |
95 | error-line = PKT-LINE("ERR" SP explanation-text) | |
96 | ---- | |
97 | ||
b31222cf SC |
98 | |
99 | SSH Transport | |
100 | ------------- | |
101 | ||
102 | Initiating the upload-pack or receive-pack processes over SSH is | |
103 | executing the binary on the server via SSH remote execution. | |
104 | It is basically equivalent to running this: | |
105 | ||
106 | $ ssh git.example.com "git-upload-pack '/project.git'" | |
107 | ||
108 | For a server to support Git pushing and pulling for a given user over | |
109 | SSH, that user needs to be able to execute one or both of those | |
110 | commands via the SSH shell that they are provided on login. On some | |
111 | systems, that shell access is limited to only being able to run those | |
112 | two commands, or even just one of them. | |
113 | ||
114 | In an ssh:// format URI, it's absolute in the URI, so the '/' after | |
115 | the host name (or port number) is sent as an argument, which is then | |
116 | read by the remote git-upload-pack exactly as is, so it's effectively | |
117 | an absolute path in the remote filesystem. | |
118 | ||
119 | git clone ssh://user@example.com/project.git | |
120 | | | |
121 | v | |
122 | ssh user@example.com "git-upload-pack '/project.git'" | |
123 | ||
124 | In a "user@host:path" format URI, its relative to the user's home | |
125 | directory, because the Git client will run: | |
126 | ||
127 | git clone user@example.com:project.git | |
128 | | | |
129 | v | |
130 | ssh user@example.com "git-upload-pack 'project.git'" | |
131 | ||
132 | The exception is if a '~' is used, in which case | |
133 | we execute it without the leading '/'. | |
134 | ||
135 | ssh://user@example.com/~alice/project.git, | |
136 | | | |
137 | v | |
138 | ssh user@example.com "git-upload-pack '~alice/project.git'" | |
139 | ||
6464679d JT |
140 | Depending on the value of the `protocol.version` configuration variable, |
141 | Git may attempt to send Extra Parameters as a colon-separated string in | |
142 | the GIT_PROTOCOL environment variable. This is done only if | |
143 | the `ssh.variant` configuration variable indicates that the ssh command | |
144 | supports passing environment variables as an argument. | |
145 | ||
b31222cf SC |
146 | A few things to remember here: |
147 | ||
148 | - The "command name" is spelled with dash (e.g. git-upload-pack), but | |
149 | this can be overridden by the client; | |
150 | ||
151 | - The repository path is always quoted with single quotes. | |
152 | ||
153 | Fetching Data From a Server | |
5316c8e9 | 154 | --------------------------- |
b31222cf SC |
155 | |
156 | When one Git repository wants to get data that a second repository | |
157 | has, the first can 'fetch' from the second. This operation determines | |
158 | what data the server has that the client does not then streams that | |
159 | data down to the client in packfile format. | |
160 | ||
161 | ||
162 | Reference Discovery | |
163 | ------------------- | |
164 | ||
165 | When the client initially connects the server will immediately respond | |
6464679d JT |
166 | with a version number (if "version=1" is sent as an Extra Parameter), |
167 | and a listing of each reference it has (all branches and tags) along | |
b31222cf SC |
168 | with the object name that each reference currently points to. |
169 | ||
6464679d | 170 | $ echo -e -n "0044git-upload-pack /schacon/gitbook.git\0host=example.com\0\0version=1\0" | |
b31222cf | 171 | nc -v example.com 9418 |
6464679d | 172 | 000aversion 1 |
5316c8e9 TA |
173 | 00887217a7c7e582c46cec22a130adf4b9d7d950fba0 HEAD\0multi_ack thin-pack |
174 | side-band side-band-64k ofs-delta shallow no-progress include-tag | |
b31222cf SC |
175 | 00441d3fcd5ced445d1abc402225c0b8a1299641f497 refs/heads/integration |
176 | 003f7217a7c7e582c46cec22a130adf4b9d7d950fba0 refs/heads/master | |
177 | 003cb88d2441cac0977faf98efc80305012112238d9d refs/tags/v0.9 | |
178 | 003c525128480b96c89e6418b1e40909bf6c5b2d580f refs/tags/v1.0 | |
179 | 003fe92df48743b7bc7d26bcaabfddde0a1e20cae47c refs/tags/v1.0^{} | |
180 | 0000 | |
181 | ||
b31222cf SC |
182 | The returned response is a pkt-line stream describing each ref and |
183 | its current value. The stream MUST be sorted by name according to | |
184 | the C locale ordering. | |
185 | ||
186 | If HEAD is a valid ref, HEAD MUST appear as the first advertised | |
187 | ref. If HEAD is not a valid ref, HEAD MUST NOT appear in the | |
188 | advertisement list at all, but other refs may still appear. | |
189 | ||
190 | The stream MUST include capability declarations behind a NUL on the | |
191 | first ref. The peeled value of a ref (that is "ref^{}") MUST be | |
192 | immediately after the ref itself, if presented. A conforming server | |
6a5d0b0a | 193 | MUST peel the ref if it's an annotated tag. |
b31222cf SC |
194 | |
195 | ---- | |
6464679d JT |
196 | advertised-refs = *1("version 1") |
197 | (no-refs / list-of-refs) | |
ad491366 | 198 | *shallow |
b31222cf SC |
199 | flush-pkt |
200 | ||
201 | no-refs = PKT-LINE(zero-id SP "capabilities^{}" | |
1c9b659d | 202 | NUL capability-list) |
b31222cf SC |
203 | |
204 | list-of-refs = first-ref *other-ref | |
205 | first-ref = PKT-LINE(obj-id SP refname | |
1c9b659d | 206 | NUL capability-list) |
b31222cf SC |
207 | |
208 | other-ref = PKT-LINE(other-tip / other-peeled) | |
1c9b659d JK |
209 | other-tip = obj-id SP refname |
210 | other-peeled = obj-id SP refname "^{}" | |
b31222cf | 211 | |
ad491366 NTND |
212 | shallow = PKT-LINE("shallow" SP obj-id) |
213 | ||
b31222cf SC |
214 | capability-list = capability *(SP capability) |
215 | capability = 1*(LC_ALPHA / DIGIT / "-" / "_") | |
216 | LC_ALPHA = %x61-7A | |
217 | ---- | |
218 | ||
219 | Server and client MUST use lowercase for obj-id, both MUST treat obj-id | |
220 | as case-insensitive. | |
221 | ||
222 | See protocol-capabilities.txt for a list of allowed server capabilities | |
223 | and descriptions. | |
224 | ||
225 | Packfile Negotiation | |
226 | -------------------- | |
a1e90b23 AN |
227 | After reference and capabilities discovery, the client can decide to |
228 | terminate the connection by sending a flush-pkt, telling the server it can | |
229 | now gracefully terminate, and disconnect, when it does not need any pack | |
230 | data. This can happen with the ls-remote command, and also can happen when | |
7560f547 | 231 | the client already is up to date. |
a1e90b23 AN |
232 | |
233 | Otherwise, it enters the negotiation phase, where the client and | |
234 | server determine what the minimal packfile necessary for transport is, | |
4a1c2695 AN |
235 | by telling the server what objects it wants, its shallow objects |
236 | (if any), and the maximum commit depth it wants (if any). The client | |
237 | will also send a list of the capabilities it wants to be in effect, | |
238 | out of what the server said it could do with the first 'want' line. | |
b31222cf SC |
239 | |
240 | ---- | |
241 | upload-request = want-list | |
4a1c2695 AN |
242 | *shallow-line |
243 | *1depth-request | |
10ac85c7 | 244 | [filter-request] |
4a1c2695 | 245 | flush-pkt |
b31222cf SC |
246 | |
247 | want-list = first-want | |
248 | *additional-want | |
4a1c2695 | 249 | |
e543b3f6 | 250 | shallow-line = PKT-LINE("shallow" SP obj-id) |
4a1c2695 | 251 | |
569e554b | 252 | depth-request = PKT-LINE("deepen" SP depth) / |
269a7a83 NTND |
253 | PKT-LINE("deepen-since" SP timestamp) / |
254 | PKT-LINE("deepen-not" SP ref) | |
b31222cf | 255 | |
1c9b659d JK |
256 | first-want = PKT-LINE("want" SP obj-id SP capability-list) |
257 | additional-want = PKT-LINE("want" SP obj-id) | |
b31222cf | 258 | |
4a1c2695 | 259 | depth = 1*DIGIT |
10ac85c7 JH |
260 | |
261 | filter-request = PKT-LINE("filter" SP filter-spec) | |
b31222cf SC |
262 | ---- |
263 | ||
264 | Clients MUST send all the obj-ids it wants from the reference | |
265 | discovery phase as 'want' lines. Clients MUST send at least one | |
266 | 'want' command in the request body. Clients MUST NOT mention an | |
267 | obj-id in a 'want' command which did not appear in the response | |
268 | obtained through ref discovery. | |
269 | ||
4a1c2695 AN |
270 | The client MUST write all obj-ids which it only has shallow copies |
271 | of (meaning that it does not have the parents of a commit) as | |
272 | 'shallow' lines so that the server is aware of the limitations of | |
af04fa2a | 273 | the client's history. |
4a1c2695 AN |
274 | |
275 | The client now sends the maximum commit history depth it wants for | |
276 | this transaction, which is the number of commits it wants from the | |
277 | tip of the history, if any, as a 'deepen' line. A depth of 0 is the | |
278 | same as not making a depth request. The client does not want to receive | |
a58088ab JL |
279 | any commits beyond this depth, nor does it want objects needed only to |
280 | complete those commits. Commits whose parents are not received as a | |
281 | result are defined as shallow and marked as such in the server. This | |
282 | information is sent back to the client in the next step. | |
4a1c2695 | 283 | |
10ac85c7 JH |
284 | The client can optionally request that pack-objects omit various |
285 | objects from the packfile using one of several filtering techniques. | |
286 | These are intended for use with partial clone and partial fetch | |
a0c9016a JT |
287 | operations. An object that does not meet a filter-spec value is |
288 | omitted unless explicitly requested in a 'want' line. See `rev-list` | |
289 | for possible filter-spec values. | |
10ac85c7 | 290 | |
4a1c2695 AN |
291 | Once all the 'want's and 'shallow's (and optional 'deepen') are |
292 | transferred, clients MUST send a flush-pkt, to tell the server side | |
293 | that it is done sending the list. | |
294 | ||
295 | Otherwise, if the client sent a positive depth request, the server | |
296 | will determine which commits will and will not be shallow and | |
297 | send this information to the client. If the client did not request | |
298 | a positive depth, this step is skipped. | |
b31222cf | 299 | |
4a1c2695 AN |
300 | ---- |
301 | shallow-update = *shallow-line | |
302 | *unshallow-line | |
303 | flush-pkt | |
b31222cf | 304 | |
4a1c2695 AN |
305 | shallow-line = PKT-LINE("shallow" SP obj-id) |
306 | ||
307 | unshallow-line = PKT-LINE("unshallow" SP obj-id) | |
308 | ---- | |
309 | ||
310 | If the client has requested a positive depth, the server will compute | |
01f7d7f1 PO |
311 | the set of commits which are no deeper than the desired depth. The set |
312 | of commits start at the client's wants. | |
313 | ||
314 | The server writes 'shallow' lines for each | |
4a1c2695 AN |
315 | commit whose parents will not be sent as a result. The server writes |
316 | an 'unshallow' line for each commit which the client has indicated is | |
317 | shallow, but is no longer shallow at the currently requested depth | |
318 | (that is, its parents will now be sent). The server MUST NOT mark | |
319 | as unshallow anything which the client has not indicated was shallow. | |
b31222cf SC |
320 | |
321 | Now the client will send a list of the obj-ids it has using 'have' | |
4a1c2695 AN |
322 | lines, so the server can make a packfile that only contains the objects |
323 | that the client needs. In multi_ack mode, the canonical implementation | |
324 | will send up to 32 of these at a time, then will send a flush-pkt. The | |
325 | canonical implementation will skip ahead and send the next 32 immediately, | |
326 | so that there is always a block of 32 "in-flight on the wire" at a time. | |
327 | ||
328 | ---- | |
329 | upload-haves = have-list | |
330 | compute-end | |
331 | ||
332 | have-list = *have-line | |
1c9b659d | 333 | have-line = PKT-LINE("have" SP obj-id) |
4a1c2695 AN |
334 | compute-end = flush-pkt / PKT-LINE("done") |
335 | ---- | |
b31222cf SC |
336 | |
337 | If the server reads 'have' lines, it then will respond by ACKing any | |
338 | of the obj-ids the client said it had that the server also has. The | |
339 | server will ACK obj-ids differently depending on which ack mode is | |
340 | chosen by the client. | |
341 | ||
342 | In multi_ack mode: | |
343 | ||
344 | * the server will respond with 'ACK obj-id continue' for any common | |
345 | commits. | |
346 | ||
347 | * once the server has found an acceptable common base commit and is | |
348 | ready to make a packfile, it will blindly ACK all 'have' obj-ids | |
349 | back to the client. | |
350 | ||
280abfd4 | 351 | * the server will then send a 'NAK' and then wait for another response |
b31222cf SC |
352 | from the client - either a 'done' or another list of 'have' lines. |
353 | ||
354 | In multi_ack_detailed mode: | |
355 | ||
356 | * the server will differentiate the ACKs where it is signaling | |
357 | that it is ready to send data with 'ACK obj-id ready' lines, and | |
358 | signals the identified common commits with 'ACK obj-id common' lines. | |
359 | ||
360 | Without either multi_ack or multi_ack_detailed: | |
361 | ||
362 | * upload-pack sends "ACK obj-id" on the first common object it finds. | |
363 | After that it says nothing until the client gives it a "done". | |
364 | ||
365 | * upload-pack sends "NAK" on a flush-pkt if no common object | |
366 | has been found yet. If one has been found, and thus an ACK | |
6a5d0b0a | 367 | was already sent, it's silent on the flush-pkt. |
b31222cf SC |
368 | |
369 | After the client has gotten enough ACK responses that it can determine | |
370 | that the server has enough information to send an efficient packfile | |
371 | (in the canonical implementation, this is determined when it has received | |
372 | enough ACKs that it can color everything left in the --date-order queue | |
373 | as common with the server, or the --date-order queue is empty), or the | |
374 | client determines that it wants to give up (in the canonical implementation, | |
375 | this is determined when the client sends 256 'have' lines without getting | |
376 | any of them ACKed by the server - meaning there is nothing in common and | |
6a5d0b0a | 377 | the server should just send all of its objects), then the client will send |
b31222cf | 378 | a 'done' command. The 'done' command signals to the server that the client |
6a5d0b0a | 379 | is ready to receive its packfile data. |
b31222cf SC |
380 | |
381 | However, the 256 limit *only* turns on in the canonical client | |
382 | implementation if we have received at least one "ACK %s continue" | |
383 | during a prior round. This helps to ensure that at least one common | |
384 | ancestor is found before we give up entirely. | |
385 | ||
386 | Once the 'done' line is read from the client, the server will either | |
32752e96 NTND |
387 | send a final 'ACK obj-id' or it will send a 'NAK'. 'obj-id' is the object |
388 | name of the last commit determined to be common. The server only sends | |
b31222cf SC |
389 | ACK after 'done' if there is at least one common base and multi_ack or |
390 | multi_ack_detailed is enabled. The server always sends NAK after 'done' | |
391 | if there is no common base found. | |
392 | ||
8e2c7bef JT |
393 | Instead of 'ACK' or 'NAK', the server may send an error message (for |
394 | example, if it does not recognize an object in a 'want' line received | |
395 | from the client). | |
396 | ||
6a5d0b0a | 397 | Then the server will start sending its packfile data. |
b31222cf SC |
398 | |
399 | ---- | |
8e2c7bef | 400 | server-response = *ack_multi ack / nak / error-line |
1c9b659d | 401 | ack_multi = PKT-LINE("ACK" SP obj-id ack_status) |
b31222cf | 402 | ack_status = "continue" / "common" / "ready" |
1c9b659d JK |
403 | ack = PKT-LINE("ACK" SP obj-id) |
404 | nak = PKT-LINE("NAK") | |
8e2c7bef | 405 | error-line = PKT-LINE("ERR" SP explanation-text) |
b31222cf SC |
406 | ---- |
407 | ||
408 | A simple clone may look like this (with no 'have' lines): | |
409 | ||
410 | ---- | |
79135e4c | 411 | C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \ |
b31222cf SC |
412 | side-band-64k ofs-delta\n |
413 | C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n | |
414 | C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n | |
415 | C: 0032want 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n | |
416 | C: 0032want 74730d410fcb6603ace96f1dc55ea6196122532d\n | |
417 | C: 0000 | |
418 | C: 0009done\n | |
419 | ||
420 | S: 0008NAK\n | |
421 | S: [PACKFILE] | |
422 | ---- | |
423 | ||
424 | An incremental update (fetch) response might look like this: | |
425 | ||
426 | ---- | |
79135e4c | 427 | C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \ |
b31222cf SC |
428 | side-band-64k ofs-delta\n |
429 | C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n | |
430 | C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n | |
431 | C: 0000 | |
432 | C: 0032have 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n | |
433 | C: [30 more have lines] | |
434 | C: 0032have 74730d410fcb6603ace96f1dc55ea6196122532d\n | |
435 | C: 0000 | |
436 | ||
437 | S: 003aACK 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01 continue\n | |
438 | S: 003aACK 74730d410fcb6603ace96f1dc55ea6196122532d continue\n | |
439 | S: 0008NAK\n | |
440 | ||
441 | C: 0009done\n | |
442 | ||
c8a97906 | 443 | S: 0031ACK 74730d410fcb6603ace96f1dc55ea6196122532d\n |
b31222cf SC |
444 | S: [PACKFILE] |
445 | ---- | |
446 | ||
447 | ||
448 | Packfile Data | |
449 | ------------- | |
450 | ||
451 | Now that the client and server have finished negotiation about what | |
452 | the minimal amount of data that needs to be sent to the client is, the server | |
453 | will construct and send the required data in packfile format. | |
454 | ||
455 | See pack-format.txt for what the packfile itself actually looks like. | |
456 | ||
457 | If 'side-band' or 'side-band-64k' capabilities have been specified by | |
458 | the client, the server will send the packfile data multiplexed. | |
459 | ||
460 | Each packet starting with the packet-line length of the amount of data | |
461 | that follows, followed by a single byte specifying the sideband the | |
462 | following data is coming in on. | |
463 | ||
464 | In 'side-band' mode, it will send up to 999 data bytes plus 1 control | |
465 | code, for a total of up to 1000 bytes in a pkt-line. In 'side-band-64k' | |
466 | mode it will send up to 65519 data bytes plus 1 control code, for a | |
467 | total of up to 65520 bytes in a pkt-line. | |
468 | ||
469 | The sideband byte will be a '1', '2' or a '3'. Sideband '1' will contain | |
470 | packfile data, sideband '2' will be used for progress information that the | |
471 | client will generally print to stderr and sideband '3' is used for error | |
472 | information. | |
473 | ||
474 | If no 'side-band' capability was specified, the server will stream the | |
475 | entire packfile without multiplexing. | |
476 | ||
477 | ||
478 | Pushing Data To a Server | |
5316c8e9 | 479 | ------------------------ |
b31222cf SC |
480 | |
481 | Pushing data to a server will invoke the 'receive-pack' process on the | |
482 | server, which will allow the client to tell it which references it should | |
483 | update and then send all the data the server will need for those new | |
484 | references to be complete. Once all the data is received and validated, | |
485 | the server will then update its references to what the client specified. | |
486 | ||
487 | Authentication | |
488 | -------------- | |
489 | ||
490 | The protocol itself contains no authentication mechanisms. That is to be | |
491 | handled by the transport, such as SSH, before the 'receive-pack' process is | |
492 | invoked. If 'receive-pack' is configured over the Git transport, those | |
493 | repositories will be writable by anyone who can access that port (9418) as | |
494 | that transport is unauthenticated. | |
495 | ||
496 | Reference Discovery | |
497 | ------------------- | |
498 | ||
499 | The reference discovery phase is done nearly the same way as it is in the | |
500 | fetching protocol. Each reference obj-id and name on the server is sent | |
501 | in packet-line format to the client, followed by a flush-pkt. The only | |
502 | real difference is that the capability listing is different - the only | |
c714e45f SB |
503 | possible values are 'report-status', 'delete-refs', 'ofs-delta' and |
504 | 'push-options'. | |
b31222cf SC |
505 | |
506 | Reference Update Request and Packfile Transfer | |
507 | ---------------------------------------------- | |
508 | ||
509 | Once the client knows what references the server is at, it can send a | |
510 | list of reference update requests. For each reference on the server | |
511 | that it wants to update, it sends a line listing the obj-id currently on | |
512 | the server, the obj-id the client would like to update it to and the name | |
513 | of the reference. | |
514 | ||
cbaf82cc | 515 | This list is followed by a flush-pkt. |
b31222cf SC |
516 | |
517 | ---- | |
cbaf82cc | 518 | update-requests = *shallow ( command-list | push-cert ) |
5dbd7676 | 519 | |
1c9b659d | 520 | shallow = PKT-LINE("shallow" SP obj-id) |
b31222cf | 521 | |
1c9b659d JK |
522 | command-list = PKT-LINE(command NUL capability-list) |
523 | *PKT-LINE(command) | |
b31222cf SC |
524 | flush-pkt |
525 | ||
526 | command = create / delete / update | |
527 | create = zero-id SP new-id SP name | |
528 | delete = old-id SP zero-id SP name | |
529 | update = old-id SP new-id SP name | |
530 | ||
531 | old-id = obj-id | |
532 | new-id = obj-id | |
533 | ||
4adf569d JH |
534 | push-cert = PKT-LINE("push-cert" NUL capability-list LF) |
535 | PKT-LINE("certificate version 0.1" LF) | |
536 | PKT-LINE("pusher" SP ident LF) | |
9be89160 | 537 | PKT-LINE("pushee" SP url LF) |
b89363e4 | 538 | PKT-LINE("nonce" SP nonce LF) |
cbaf82cc | 539 | *PKT-LINE("push-option" SP push-option LF) |
4adf569d JH |
540 | PKT-LINE(LF) |
541 | *PKT-LINE(command LF) | |
542 | *PKT-LINE(gpg-signature-lines LF) | |
543 | PKT-LINE("push-cert-end" LF) | |
544 | ||
cbaf82cc JT |
545 | push-option = 1*( VCHAR | SP ) |
546 | ---- | |
547 | ||
548 | If the server has advertised the 'push-options' capability and the client has | |
549 | specified 'push-options' as part of the capability list above, the client then | |
550 | sends its push options followed by a flush-pkt. | |
551 | ||
552 | ---- | |
553 | push-options = *PKT-LINE(push-option) flush-pkt | |
554 | ---- | |
555 | ||
556 | For backwards compatibility with older Git servers, if the client sends a push | |
557 | cert and push options, it MUST send its push options both embedded within the | |
558 | push cert and after the push cert. (Note that the push options within the cert | |
559 | are prefixed, but the push options after the cert are not.) Both these lists | |
560 | MUST be the same, modulo the prefix. | |
561 | ||
562 | After that the packfile that | |
563 | should contain all the objects that the server will need to complete the new | |
564 | references will be sent. | |
565 | ||
566 | ---- | |
567 | packfile = "PACK" 28*(OCTET) | |
b31222cf SC |
568 | ---- |
569 | ||
570 | If the receiving end does not support delete-refs, the sending end MUST | |
571 | NOT ask for delete command. | |
572 | ||
4adf569d JH |
573 | If the receiving end does not support push-cert, the sending end |
574 | MUST NOT send a push-cert command. When a push-cert command is | |
575 | sent, command-list MUST NOT be sent; the commands recorded in the | |
576 | push certificate is used instead. | |
577 | ||
3890dae9 | 578 | The packfile MUST NOT be sent if the only command used is 'delete'. |
b31222cf | 579 | |
3890dae9 | 580 | A packfile MUST be sent if either create or update command is used, |
b31222cf | 581 | even if the server already has all the necessary objects. In this |
3890dae9 | 582 | case the client MUST send an empty packfile. The only time this |
b31222cf SC |
583 | is likely to happen is if the client is creating |
584 | a new branch or a tag that points to an existing obj-id. | |
585 | ||
586 | The server will receive the packfile, unpack it, then validate each | |
587 | reference that is being updated that it hasn't changed while the request | |
588 | was being processed (the obj-id is still the same as the old-id), and | |
589 | it will run any update hooks to make sure that the update is acceptable. | |
590 | If all of that is fine, the server will then update the references. | |
591 | ||
4adf569d JH |
592 | Push Certificate |
593 | ---------------- | |
594 | ||
595 | A push certificate begins with a set of header lines. After the | |
596 | header and an empty line, the protocol commands follow, one per | |
832c0e5e | 597 | line. Note that the trailing LF in push-cert PKT-LINEs is _not_ |
1c9b659d | 598 | optional; it must be present. |
4adf569d JH |
599 | |
600 | Currently, the following header fields are defined: | |
601 | ||
602 | `pusher` ident:: | |
603 | Identify the GPG key in "Human Readable Name <email@address>" | |
604 | format. | |
605 | ||
9be89160 JH |
606 | `pushee` url:: |
607 | The repository URL (anonymized, if the URL contains | |
608 | authentication material) the user who ran `git push` | |
609 | intended to push into. | |
610 | ||
b89363e4 JH |
611 | `nonce` nonce:: |
612 | The 'nonce' string the receiving repository asked the | |
613 | pushing user to include in the certificate, to prevent | |
614 | replay attacks. | |
615 | ||
4adf569d JH |
616 | The GPG signature lines are a detached signature for the contents |
617 | recorded in the push certificate before the signature block begins. | |
618 | The detached signature is used to certify that the commands were | |
619 | given by the pusher, who must be the signer. | |
620 | ||
b31222cf SC |
621 | Report Status |
622 | ------------- | |
623 | ||
624 | After receiving the pack data from the sender, the receiver sends a | |
625 | report if 'report-status' capability is in effect. | |
626 | It is a short listing of what happened in that update. It will first | |
627 | list the status of the packfile unpacking as either 'unpack ok' or | |
628 | 'unpack [error]'. Then it will list the status for each of the references | |
629 | that it tried to update. Each line is either 'ok [refname]' if the | |
630 | update was successful, or 'ng [refname] [error]' if the update was not. | |
631 | ||
632 | ---- | |
633 | report-status = unpack-status | |
634 | 1*(command-status) | |
635 | flush-pkt | |
636 | ||
1c9b659d | 637 | unpack-status = PKT-LINE("unpack" SP unpack-result) |
b31222cf SC |
638 | unpack-result = "ok" / error-msg |
639 | ||
640 | command-status = command-ok / command-fail | |
1c9b659d JK |
641 | command-ok = PKT-LINE("ok" SP refname) |
642 | command-fail = PKT-LINE("ng" SP refname SP error-msg) | |
b31222cf SC |
643 | |
644 | error-msg = 1*(OCTECT) ; where not "ok" | |
645 | ---- | |
646 | ||
647 | Updates can be unsuccessful for a number of reasons. The reference can have | |
648 | changed since the reference discovery phase was originally sent, meaning | |
649 | someone pushed in the meantime. The reference being pushed could be a | |
650 | non-fast-forward reference and the update hooks or configuration could be | |
651 | set to not allow that, etc. Also, some references can be updated while others | |
652 | can be rejected. | |
653 | ||
654 | An example client/server communication might look like this: | |
655 | ||
656 | ---- | |
657 | S: 007c74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n | |
658 | S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n | |
659 | S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n | |
660 | S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n | |
661 | S: 0000 | |
662 | ||
663 | C: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n | |
664 | C: 003e74730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n | |
665 | C: 0000 | |
666 | C: [PACKDATA] | |
667 | ||
c8a97906 TRC |
668 | S: 000eunpack ok\n |
669 | S: 0018ok refs/heads/debug\n | |
670 | S: 002ang refs/heads/master non-fast-forward\n | |
b31222cf | 671 | ---- |