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1gitprotocol-pack(5)
2===================
3
4NAME
5----
6gitprotocol-pack - How packs are transferred over-the-wire
7
8SYNOPSIS
9--------
10[verse]
11<over-the-wire-protocol>
12
13DESCRIPTION
14-----------
15
16Git supports transferring data in packfiles over the ssh://, git://, http:// and
17file:// transports. There exist two sets of protocols, one for pushing
18data from a client to a server and another for fetching data from a
19server to a client. The three transports (ssh, git, file) use the same
20protocol to transfer data. http is documented in linkgit:gitprotocol-http[5].
21
22The processes invoked in the canonical Git implementation are 'upload-pack'
23on the server side and 'fetch-pack' on the client side for fetching data;
24then 'receive-pack' on the server and 'send-pack' on the client for pushing
25data. The protocol functions to have a server tell a client what is
26currently on the server, then for the two to negotiate the smallest amount
27of data to send in order to fully update one or the other.
28
29pkt-line Format
30---------------
31
32The descriptions below build on the pkt-line format described in
33linkgit:gitprotocol-common[5]. When the grammar indicates `PKT-LINE(...)`, unless
34otherwise noted the usual pkt-line LF rules apply: the sender SHOULD
35include a LF, but the receiver MUST NOT complain if it is not present.
36
37An error packet is a special pkt-line that contains an error string.
38
39----
40 error-line = PKT-LINE("ERR" SP explanation-text)
41----
42
43Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY
44be sent. Once this packet is sent by a client or a server, the data transfer
45process defined in this protocol is terminated.
46
47Transports
48----------
49There are three transports over which the packfile protocol is
50initiated. The Git transport is a simple, unauthenticated server that
51takes the command (almost always 'upload-pack', though Git
52servers can be configured to be globally writable, in which 'receive-
53pack' initiation is also allowed) with which the client wishes to
54communicate and executes it and connects it to the requesting
55process.
56
57In the SSH transport, the client just runs the 'upload-pack'
58or 'receive-pack' process on the server over the SSH protocol and then
59communicates with that invoked process over the SSH connection.
60
61The file:// transport runs the 'upload-pack' or 'receive-pack'
62process locally and communicates with it over a pipe.
63
64Extra Parameters
65----------------
66
67The protocol provides a mechanism in which clients can send additional
68information in its first message to the server. These are called "Extra
69Parameters", and are supported by the Git, SSH, and HTTP protocols.
70
71Each Extra Parameter takes the form of `<key>=<value>` or `<key>`.
72
73Servers that receive any such Extra Parameters MUST ignore all
74unrecognized keys. Currently, the only Extra Parameter recognized is
75"version" with a value of '1' or '2'. See linkgit:gitprotocol-v2[5] for more
76information on protocol version 2.
77
78Git Transport
79-------------
80
81The Git transport starts off by sending the command and repository
82on the wire using the pkt-line format, followed by a NUL byte and a
83hostname parameter, terminated by a NUL byte.
84
85 0033git-upload-pack /project.git\0host=myserver.com\0
86
87The transport may send Extra Parameters by adding an additional NUL
88byte, and then adding one or more NUL-terminated strings:
89
90 003egit-upload-pack /project.git\0host=myserver.com\0\0version=1\0
91
92--
93 git-proto-request = request-command SP pathname NUL
94 [ host-parameter NUL ] [ NUL extra-parameters ]
95 request-command = "git-upload-pack" / "git-receive-pack" /
96 "git-upload-archive" ; case sensitive
97 pathname = *( %x01-ff ) ; exclude NUL
98 host-parameter = "host=" hostname [ ":" port ]
99 extra-parameters = 1*extra-parameter
100 extra-parameter = 1*( %x01-ff ) NUL
101--
102
103host-parameter is used for the
104git-daemon name based virtual hosting. See --interpolated-path
105option to git daemon, with the %H/%CH format characters.
106
107Basically what the Git client is doing to connect to an 'upload-pack'
108process on the server side over the Git protocol is this:
109
110 $ echo -e -n \
111 "003agit-upload-pack /schacon/gitbook.git\0host=example.com\0" |
112 nc -v example.com 9418
113
114
115SSH Transport
116-------------
117
118Initiating the upload-pack or receive-pack processes over SSH is
119executing the binary on the server via SSH remote execution.
120It is basically equivalent to running this:
121
122 $ ssh git.example.com "git-upload-pack '/project.git'"
123
124For a server to support Git pushing and pulling for a given user over
125SSH, that user needs to be able to execute one or both of those
126commands via the SSH shell that they are provided on login. On some
127systems, that shell access is limited to only being able to run those
128two commands, or even just one of them.
129
130In an ssh:// format URI, it's absolute in the URI, so the '/' after
131the host name (or port number) is sent as an argument, which is then
132read by the remote git-upload-pack exactly as is, so it's effectively
133an absolute path in the remote filesystem.
134
135 git clone ssh://user@example.com/project.git
136 |
137 v
138 ssh user@example.com "git-upload-pack '/project.git'"
139
140In a "user@host:path" format URI, it's relative to the user's home
141directory, because the Git client will run:
142
143 git clone user@example.com:project.git
144 |
145 v
146 ssh user@example.com "git-upload-pack 'project.git'"
147
148The exception is if a '~' is used, in which case
149we execute it without the leading '/'.
150
151 ssh://user@example.com/~alice/project.git,
152 |
153 v
154 ssh user@example.com "git-upload-pack '~alice/project.git'"
155
156Depending on the value of the `protocol.version` configuration variable,
157Git may attempt to send Extra Parameters as a colon-separated string in
158the GIT_PROTOCOL environment variable. This is done only if
159the `ssh.variant` configuration variable indicates that the ssh command
160supports passing environment variables as an argument.
161
162A few things to remember here:
163
164- The "command name" is spelled with dash (e.g. git-upload-pack), but
165 this can be overridden by the client;
166
167- The repository path is always quoted with single quotes.
168
169Fetching Data From a Server
170---------------------------
171
172When one Git repository wants to get data that a second repository
173has, the first can 'fetch' from the second. This operation determines
174what data the server has that the client does not then streams that
175data down to the client in packfile format.
176
177
178Reference Discovery
179-------------------
180
181When the client initially connects the server will immediately respond
182with a version number (if "version=1" is sent as an Extra Parameter),
183and a listing of each reference it has (all branches and tags) along
184with the object name that each reference currently points to.
185
186 $ echo -e -n "0045git-upload-pack /schacon/gitbook.git\0host=example.com\0\0version=1\0" |
187 nc -v example.com 9418
188 000eversion 1
189 00887217a7c7e582c46cec22a130adf4b9d7d950fba0 HEAD\0multi_ack thin-pack
190 side-band side-band-64k ofs-delta shallow no-progress include-tag
191 00441d3fcd5ced445d1abc402225c0b8a1299641f497 refs/heads/integration
192 003f7217a7c7e582c46cec22a130adf4b9d7d950fba0 refs/heads/master
193 003cb88d2441cac0977faf98efc80305012112238d9d refs/tags/v0.9
194 003c525128480b96c89e6418b1e40909bf6c5b2d580f refs/tags/v1.0
195 003fe92df48743b7bc7d26bcaabfddde0a1e20cae47c refs/tags/v1.0^{}
196 0000
197
198The returned response is a pkt-line stream describing each ref and
199its current value. The stream MUST be sorted by name according to
200the C locale ordering.
201
202If HEAD is a valid ref, HEAD MUST appear as the first advertised
203ref. If HEAD is not a valid ref, HEAD MUST NOT appear in the
204advertisement list at all, but other refs may still appear.
205
206The stream MUST include capability declarations behind a NUL on the
207first ref. The peeled value of a ref (that is "ref^{}") MUST be
208immediately after the ref itself, if presented. A conforming server
209MUST peel the ref if it's an annotated tag.
210
211----
212 advertised-refs = *1("version 1")
213 (no-refs / list-of-refs)
214 *shallow
215 flush-pkt
216
217 no-refs = PKT-LINE(zero-id SP "capabilities^{}"
218 NUL capability-list)
219
220 list-of-refs = first-ref *other-ref
221 first-ref = PKT-LINE(obj-id SP refname
222 NUL capability-list)
223
224 other-ref = PKT-LINE(other-tip / other-peeled)
225 other-tip = obj-id SP refname
226 other-peeled = obj-id SP refname "^{}"
227
228 shallow = PKT-LINE("shallow" SP obj-id)
229
230 capability-list = capability *(SP capability)
231 capability = 1*(LC_ALPHA / DIGIT / "-" / "_")
232 LC_ALPHA = %x61-7A
233----
234
235Server and client MUST use lowercase for obj-id, both MUST treat obj-id
236as case-insensitive.
237
238See protocol-capabilities.txt for a list of allowed server capabilities
239and descriptions.
240
241Packfile Negotiation
242--------------------
243After reference and capabilities discovery, the client can decide to
244terminate the connection by sending a flush-pkt, telling the server it can
245now gracefully terminate, and disconnect, when it does not need any pack
246data. This can happen with the ls-remote command, and also can happen when
247the client already is up to date.
248
249Otherwise, it enters the negotiation phase, where the client and
250server determine what the minimal packfile necessary for transport is,
251by telling the server what objects it wants, its shallow objects
252(if any), and the maximum commit depth it wants (if any). The client
253will also send a list of the capabilities it wants to be in effect,
254out of what the server said it could do with the first 'want' line.
255
256----
257 upload-request = want-list
258 *shallow-line
259 *1depth-request
260 [filter-request]
261 flush-pkt
262
263 want-list = first-want
264 *additional-want
265
266 shallow-line = PKT-LINE("shallow" SP obj-id)
267
268 depth-request = PKT-LINE("deepen" SP depth) /
269 PKT-LINE("deepen-since" SP timestamp) /
270 PKT-LINE("deepen-not" SP ref)
271
272 first-want = PKT-LINE("want" SP obj-id SP capability-list)
273 additional-want = PKT-LINE("want" SP obj-id)
274
275 depth = 1*DIGIT
276
277 filter-request = PKT-LINE("filter" SP filter-spec)
278----
279
280Clients MUST send all the obj-ids it wants from the reference
281discovery phase as 'want' lines. Clients MUST send at least one
282'want' command in the request body. Clients MUST NOT mention an
283obj-id in a 'want' command which did not appear in the response
284obtained through ref discovery.
285
286The client MUST write all obj-ids which it only has shallow copies
287of (meaning that it does not have the parents of a commit) as
288'shallow' lines so that the server is aware of the limitations of
289the client's history.
290
291The client now sends the maximum commit history depth it wants for
292this transaction, which is the number of commits it wants from the
293tip of the history, if any, as a 'deepen' line. A depth of 0 is the
294same as not making a depth request. The client does not want to receive
295any commits beyond this depth, nor does it want objects needed only to
296complete those commits. Commits whose parents are not received as a
297result are defined as shallow and marked as such in the server. This
298information is sent back to the client in the next step.
299
300The client can optionally request that pack-objects omit various
301objects from the packfile using one of several filtering techniques.
302These are intended for use with partial clone and partial fetch
303operations. An object that does not meet a filter-spec value is
304omitted unless explicitly requested in a 'want' line. See `rev-list`
305for possible filter-spec values.
306
307Once all the 'want's and 'shallow's (and optional 'deepen') are
308transferred, clients MUST send a flush-pkt, to tell the server side
309that it is done sending the list.
310
311Otherwise, if the client sent a positive depth request, the server
312will determine which commits will and will not be shallow and
313send this information to the client. If the client did not request
314a positive depth, this step is skipped.
315
316----
317 shallow-update = *shallow-line
318 *unshallow-line
319 flush-pkt
320
321 shallow-line = PKT-LINE("shallow" SP obj-id)
322
323 unshallow-line = PKT-LINE("unshallow" SP obj-id)
324----
325
326If the client has requested a positive depth, the server will compute
327the set of commits which are no deeper than the desired depth. The set
328of commits starts at the client's wants.
329
330The server writes 'shallow' lines for each
331commit whose parents will not be sent as a result. The server writes
332an 'unshallow' line for each commit which the client has indicated is
333shallow, but is no longer shallow at the currently requested depth
334(that is, its parents will now be sent). The server MUST NOT mark
335as unshallow anything which the client has not indicated was shallow.
336
337Now the client will send a list of the obj-ids it has using 'have'
338lines, so the server can make a packfile that only contains the objects
339that the client needs. In multi_ack mode, the canonical implementation
340will send up to 32 of these at a time, then will send a flush-pkt. The
341canonical implementation will skip ahead and send the next 32 immediately,
342so that there is always a block of 32 "in-flight on the wire" at a time.
343
344----
345 upload-haves = have-list
346 compute-end
347
348 have-list = *have-line
349 have-line = PKT-LINE("have" SP obj-id)
350 compute-end = flush-pkt / PKT-LINE("done")
351----
352
353If the server reads 'have' lines, it then will respond by ACKing any
354of the obj-ids the client said it had that the server also has. The
355server will ACK obj-ids differently depending on which ack mode is
356chosen by the client.
357
358In multi_ack mode:
359
360 * the server will respond with 'ACK obj-id continue' for any common
361 commits.
362
363 * once the server has found an acceptable common base commit and is
364 ready to make a packfile, it will blindly ACK all 'have' obj-ids
365 back to the client.
366
367 * the server will then send a 'NAK' and then wait for another response
368 from the client - either a 'done' or another list of 'have' lines.
369
370In multi_ack_detailed mode:
371
372 * the server will differentiate the ACKs where it is signaling
373 that it is ready to send data with 'ACK obj-id ready' lines, and
374 signals the identified common commits with 'ACK obj-id common' lines.
375
376Without either multi_ack or multi_ack_detailed:
377
378 * upload-pack sends "ACK obj-id" on the first common object it finds.
379 After that it says nothing until the client gives it a "done".
380
381 * upload-pack sends "NAK" on a flush-pkt if no common object
382 has been found yet. If one has been found, and thus an ACK
383 was already sent, it's silent on the flush-pkt.
384
385After the client has gotten enough ACK responses that it can determine
386that the server has enough information to send an efficient packfile
387(in the canonical implementation, this is determined when it has received
388enough ACKs that it can color everything left in the --date-order queue
389as common with the server, or the --date-order queue is empty), or the
390client determines that it wants to give up (in the canonical implementation,
391this is determined when the client sends 256 'have' lines without getting
392any of them ACKed by the server - meaning there is nothing in common and
393the server should just send all of its objects), then the client will send
394a 'done' command. The 'done' command signals to the server that the client
395is ready to receive its packfile data.
396
397However, the 256 limit *only* turns on in the canonical client
398implementation if we have received at least one "ACK %s continue"
399during a prior round. This helps to ensure that at least one common
400ancestor is found before we give up entirely.
401
402Once the 'done' line is read from the client, the server will either
403send a final 'ACK obj-id' or it will send a 'NAK'. 'obj-id' is the object
404name of the last commit determined to be common. The server only sends
405ACK after 'done' if there is at least one common base and multi_ack or
406multi_ack_detailed is enabled. The server always sends NAK after 'done'
407if there is no common base found.
408
409Instead of 'ACK' or 'NAK', the server may send an error message (for
410example, if it does not recognize an object in a 'want' line received
411from the client).
412
413Then the server will start sending its packfile data.
414
415----
416 server-response = *ack_multi ack / nak
417 ack_multi = PKT-LINE("ACK" SP obj-id ack_status)
418 ack_status = "continue" / "common" / "ready"
419 ack = PKT-LINE("ACK" SP obj-id)
420 nak = PKT-LINE("NAK")
421----
422
423A simple clone may look like this (with no 'have' lines):
424
425----
426 C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \
427 side-band-64k ofs-delta\n
428 C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n
429 C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n
430 C: 0032want 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n
431 C: 0032want 74730d410fcb6603ace96f1dc55ea6196122532d\n
432 C: 0000
433 C: 0009done\n
434
435 S: 0008NAK\n
436 S: [PACKFILE]
437----
438
439An incremental update (fetch) response might look like this:
440
441----
442 C: 0054want 74730d410fcb6603ace96f1dc55ea6196122532d multi_ack \
443 side-band-64k ofs-delta\n
444 C: 0032want 7d1665144a3a975c05f1f43902ddaf084e784dbe\n
445 C: 0032want 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a\n
446 C: 0000
447 C: 0032have 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01\n
448 C: [30 more have lines]
449 C: 0032have 74730d410fcb6603ace96f1dc55ea6196122532d\n
450 C: 0000
451
452 S: 003aACK 7e47fe2bd8d01d481f44d7af0531bd93d3b21c01 continue\n
453 S: 003aACK 74730d410fcb6603ace96f1dc55ea6196122532d continue\n
454 S: 0008NAK\n
455
456 C: 0009done\n
457
458 S: 0031ACK 74730d410fcb6603ace96f1dc55ea6196122532d\n
459 S: [PACKFILE]
460----
461
462
463Packfile Data
464-------------
465
466Now that the client and server have finished negotiation about what
467the minimal amount of data that needs to be sent to the client is, the server
468will construct and send the required data in packfile format.
469
470See linkgit:gitformat-pack[5] for what the packfile itself actually looks like.
471
472If 'side-band' or 'side-band-64k' capabilities have been specified by
473the client, the server will send the packfile data multiplexed.
474
475Each packet starting with the packet-line length of the amount of data
476that follows, followed by a single byte specifying the sideband the
477following data is coming in on.
478
479In 'side-band' mode, it will send up to 999 data bytes plus 1 control
480code, for a total of up to 1000 bytes in a pkt-line. In 'side-band-64k'
481mode it will send up to 65519 data bytes plus 1 control code, for a
482total of up to 65520 bytes in a pkt-line.
483
484The sideband byte will be a '1', '2' or a '3'. Sideband '1' will contain
485packfile data, sideband '2' will be used for progress information that the
486client will generally print to stderr and sideband '3' is used for error
487information.
488
489If no 'side-band' capability was specified, the server will stream the
490entire packfile without multiplexing.
491
492
493Pushing Data To a Server
494------------------------
495
496Pushing data to a server will invoke the 'receive-pack' process on the
497server, which will allow the client to tell it which references it should
498update and then send all the data the server will need for those new
499references to be complete. Once all the data is received and validated,
500the server will then update its references to what the client specified.
501
502Authentication
503--------------
504
505The protocol itself contains no authentication mechanisms. That is to be
506handled by the transport, such as SSH, before the 'receive-pack' process is
507invoked. If 'receive-pack' is configured over the Git transport, those
508repositories will be writable by anyone who can access that port (9418) as
509that transport is unauthenticated.
510
511Reference Discovery
512-------------------
513
514The reference discovery phase is done nearly the same way as it is in the
515fetching protocol. Each reference obj-id and name on the server is sent
516in packet-line format to the client, followed by a flush-pkt. The only
517real difference is that the capability listing is different - the only
518possible values are 'report-status', 'report-status-v2', 'delete-refs',
519'ofs-delta', 'atomic' and 'push-options'.
520
521Reference Update Request and Packfile Transfer
522----------------------------------------------
523
524Once the client knows what references the server is at, it can send a
525list of reference update requests. For each reference on the server
526that it wants to update, it sends a line listing the obj-id currently on
527the server, the obj-id the client would like to update it to and the name
528of the reference.
529
530This list is followed by a flush-pkt.
531
532----
533 update-requests = *shallow ( command-list | push-cert )
534
535 shallow = PKT-LINE("shallow" SP obj-id)
536
537 command-list = PKT-LINE(command NUL capability-list)
538 *PKT-LINE(command)
539 flush-pkt
540
541 command = create / delete / update
542 create = zero-id SP new-id SP name
543 delete = old-id SP zero-id SP name
544 update = old-id SP new-id SP name
545
546 old-id = obj-id
547 new-id = obj-id
548
549 push-cert = PKT-LINE("push-cert" NUL capability-list LF)
550 PKT-LINE("certificate version 0.1" LF)
551 PKT-LINE("pusher" SP ident LF)
552 PKT-LINE("pushee" SP url LF)
553 PKT-LINE("nonce" SP nonce LF)
554 *PKT-LINE("push-option" SP push-option LF)
555 PKT-LINE(LF)
556 *PKT-LINE(command LF)
557 *PKT-LINE(gpg-signature-lines LF)
558 PKT-LINE("push-cert-end" LF)
559
560 push-option = 1*( VCHAR | SP )
561----
562
563If the server has advertised the 'push-options' capability and the client has
564specified 'push-options' as part of the capability list above, the client then
565sends its push options followed by a flush-pkt.
566
567----
568 push-options = *PKT-LINE(push-option) flush-pkt
569----
570
571For backwards compatibility with older Git servers, if the client sends a push
572cert and push options, it MUST send its push options both embedded within the
573push cert and after the push cert. (Note that the push options within the cert
574are prefixed, but the push options after the cert are not.) Both these lists
575MUST be the same, modulo the prefix.
576
577After that the packfile that
578should contain all the objects that the server will need to complete the new
579references will be sent.
580
581----
582 packfile = "PACK" 28*(OCTET)
583----
584
585If the receiving end does not support delete-refs, the sending end MUST
586NOT ask for delete command.
587
588If the receiving end does not support push-cert, the sending end
589MUST NOT send a push-cert command. When a push-cert command is
590sent, command-list MUST NOT be sent; the commands recorded in the
591push certificate is used instead.
592
593The packfile MUST NOT be sent if the only command used is 'delete'.
594
595A packfile MUST be sent if either create or update command is used,
596even if the server already has all the necessary objects. In this
597case the client MUST send an empty packfile. The only time this
598is likely to happen is if the client is creating
599a new branch or a tag that points to an existing obj-id.
600
601The server will receive the packfile, unpack it, then validate each
602reference that is being updated that it hasn't changed while the request
603was being processed (the obj-id is still the same as the old-id), and
604it will run any update hooks to make sure that the update is acceptable.
605If all of that is fine, the server will then update the references.
606
607Push Certificate
608----------------
609
610A push certificate begins with a set of header lines. After the
611header and an empty line, the protocol commands follow, one per
612line. Note that the trailing LF in push-cert PKT-LINEs is _not_
613optional; it must be present.
614
615Currently, the following header fields are defined:
616
617`pusher` ident::
618 Identify the GPG key in "Human Readable Name <email@address>"
619 format.
620
621`pushee` url::
622 The repository URL (anonymized, if the URL contains
623 authentication material) the user who ran `git push`
624 intended to push into.
625
626`nonce` nonce::
627 The 'nonce' string the receiving repository asked the
628 pushing user to include in the certificate, to prevent
629 replay attacks.
630
631The GPG signature lines are a detached signature for the contents
632recorded in the push certificate before the signature block begins.
633The detached signature is used to certify that the commands were
634given by the pusher, who must be the signer.
635
636Report Status
637-------------
638
639After receiving the pack data from the sender, the receiver sends a
640report if 'report-status' or 'report-status-v2' capability is in effect.
641It is a short listing of what happened in that update. It will first
642list the status of the packfile unpacking as either 'unpack ok' or
643'unpack [error]'. Then it will list the status for each of the references
644that it tried to update. Each line is either 'ok [refname]' if the
645update was successful, or 'ng [refname] [error]' if the update was not.
646
647----
648 report-status = unpack-status
649 1*(command-status)
650 flush-pkt
651
652 unpack-status = PKT-LINE("unpack" SP unpack-result)
653 unpack-result = "ok" / error-msg
654
655 command-status = command-ok / command-fail
656 command-ok = PKT-LINE("ok" SP refname)
657 command-fail = PKT-LINE("ng" SP refname SP error-msg)
658
659 error-msg = 1*(OCTET) ; where not "ok"
660----
661
662The 'report-status-v2' capability extends the protocol by adding new option
663lines in order to support reporting of reference rewritten by the
664'proc-receive' hook. The 'proc-receive' hook may handle a command for a
665pseudo-reference which may create or update one or more references, and each
666reference may have different name, different new-oid, and different old-oid.
667
668----
669 report-status-v2 = unpack-status
670 1*(command-status-v2)
671 flush-pkt
672
673 unpack-status = PKT-LINE("unpack" SP unpack-result)
674 unpack-result = "ok" / error-msg
675
676 command-status-v2 = command-ok-v2 / command-fail
677 command-ok-v2 = command-ok
678 *option-line
679
680 command-ok = PKT-LINE("ok" SP refname)
681 command-fail = PKT-LINE("ng" SP refname SP error-msg)
682
683 error-msg = 1*(OCTET) ; where not "ok"
684
685 option-line = *1(option-refname)
686 *1(option-old-oid)
687 *1(option-new-oid)
688 *1(option-forced-update)
689
690 option-refname = PKT-LINE("option" SP "refname" SP refname)
691 option-old-oid = PKT-LINE("option" SP "old-oid" SP obj-id)
692 option-new-oid = PKT-LINE("option" SP "new-oid" SP obj-id)
693 option-force = PKT-LINE("option" SP "forced-update")
694
695----
696
697Updates can be unsuccessful for a number of reasons. The reference can have
698changed since the reference discovery phase was originally sent, meaning
699someone pushed in the meantime. The reference being pushed could be a
700non-fast-forward reference and the update hooks or configuration could be
701set to not allow that, etc. Also, some references can be updated while others
702can be rejected.
703
704An example client/server communication might look like this:
705
706----
707 S: 006274730d410fcb6603ace96f1dc55ea6196122532d refs/heads/local\0report-status delete-refs ofs-delta\n
708 S: 003e7d1665144a3a975c05f1f43902ddaf084e784dbe refs/heads/debug\n
709 S: 003f74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/master\n
710 S: 003d74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/team\n
711 S: 0000
712
713 C: 00677d1665144a3a975c05f1f43902ddaf084e784dbe 74730d410fcb6603ace96f1dc55ea6196122532d refs/heads/debug\n
714 C: 006874730d410fcb6603ace96f1dc55ea6196122532d 5a3f6be755bbb7deae50065988cbfa1ffa9ab68a refs/heads/master\n
715 C: 0000
716 C: [PACKDATA]
717
718 S: 000eunpack ok\n
719 S: 0018ok refs/heads/debug\n
720 S: 002ang refs/heads/master non-fast-forward\n
721----
722
723GIT
724---
725Part of the linkgit:git[1] suite